Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: 4129R on Friday,September 16, 2016, 07:38:56 AM
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I am exploring the feasibility, and cost, of cutting off part of the Zenith inlet manifold, and welding on a 45DCOE Weber manifold for a Lotus Twin Cam head.
It looks possible and relatively cheap compared with the cost of a new head (£3,000 ish) and the cost of a decent second hand Weber head North of £1,000, which usually is wanting some machine work, guides, valve seats etc.
I was told by a Lotus engine specialist that the cost of cutting off the inlet and grafting on a new one would be prohibitive, but I am not so sure.
If I find a cost effective way of doing this, how many of you out there would be interested in doing this? I was thinking of getting an inlet casting made up that could easily be welded to the cut back head, and if I get someone to make the casting, they would want to know how many castings to make. The greater the number of people interested, the more the cost of making up the mould for the casting would be divided up, making it cheaper for all.
I tried to contact an engineering company in the US who did this years ago, but I got no reply.
Alex in Norfolk.
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Was Omnitech (http://omnitech-engineering.com/category/automobile/auto-article/lotus-port-tuning-for-volumetric-efficiency) the folks you called? Dave Bean was the first I heard of who was selling them. It wasn't cheap and I highly suspect he took orders for Omnitech. I would guess there are shops on your side of the pond who at least used to do it, but I wonder if the engine has gotten too old for many people to want such a high dollar mod. I would also think there are fewer Stromberg heads in Europe and thus even less a market for it. For your sake, I hope I'm wrong.
Let us know what you find out.
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I need to speak to my machinist and get his take on the feasibility of the project.
Rather than weld on the Weber manifold, anyone see why they can't be bolted on instead, assuming the casting around the intake area is thick enough.
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Cutting off the old manifold flush with the head is trickier than say 1" away.
A bolt on would be much easier. I wonder what will happen when the 8 holes are drilled and tapped into the casting. Will it go into the waterway?
Alex in Norfolk.
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A bolt on would be much easier. I wonder what will happen when the 8 holes are drilled and tapped into the casting. Will it go into the waterway?
Alex in Norfolk.
Would it matter if it did ? I suppose if you were using bolts it would be a problem, but I would expect a permanent stud would be ok. It's not as if you'd be pulling the manifold section on and off, it would most likely be a fit and forget installation.
I haven't seen a Stromberg head close up but I can't imagine why it's not feasible if the later head was a modification of the original design. It might be expensive to cast a section unless you were doing a hundred, but a fabricated item might be cheaper for one or two items. If you can weld it yourself or get a cheap source of welding, say an exhaust fabricator, then I would think it's an economic project. If you have to go to a machining shop then I'm more doubtful.
Brian
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I'm pretty sure Omnitech bolted a Weber inlet manifold to a modified Stromberg head. Besided having better carbs, there were advantages in porting the input runners because they were shorter so there was more control of the grinder and bur and thus a better job.
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Well BDA, ya got me curious..... and I reckon you're right. These look familiar ? :)
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I had contacted Omnitec. No reply.
If I were to use brass or stainless steel studs into the head, if they went into the waterway, they would not corrode, so would be replaceable.
I remember old Minis had brass 1/2" nuts on the exhaust/inlet manifold studs to stop corrosion, so it must work, even with high exhaust temperatures.
All the old Elans in the UK had Zenith carbs, so there would be a market in both the US and the UK for a bolt on inlet manifold.
I have a scrap Zenith head here, so I will explore possibilities. I even bought a 45DCOE cast aluminium inlet manifold on eBay which was for a Zetec engine to see if I could use that. It had TURBSOPORT cast into the manifold. It seems the casting people (Chinese?) could not spell. I will contact Turbosport, who are not too far away from me, to explore options of casting a special manifold, costs, feasibility etc.
Alex in Norfolk.
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I'm pretty sure Omnitech bolted a Weber inlet manifold to a modified Stromberg head. Besides having better carbs, there were advantages in porting the input runners because they were shorter so there was more control of the grinder and bur and thus a better job.
I also recall in my conversations with Bean that the Stromberg head was a good candidate for Weber modification. He machines off the Stromberg intake and bolts on a Weber manifold. The question is it worth the $1350.00 for the conversion plus another $798.00 for the Weber carburetor setup (Bean also sells). :confused:
(http://www.davebean.com/images/head1a.jpg)
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Well BDA, ya got me curious..... and I reckon you're right. These look familiar ? :)
The captions on those photos look the wrong way around to me.
Alex in Norfolk.
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Apparently you don't need to weld the cast alloy, it is more like soldering using an aluminium filler rod, and oxy-acetylene to heat up the surfaces and melt the rod.
But if a bolt on manifold is cheap enough, it cannot take long to cut off the old manifold, machine the head flat using a milling machine, drill and tap 8 holes, and put liquid gasket in place to seal the joint.
Alex in Norfolk.
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Brian, that's the way I remember it.
Joe, is that current information from Bean? His website is WAY out of date. Regardless, I think it would at least be an interesting exercise to call them over at Bean and ask about it. Bean used to have a machine shop - he built my engine - but I don't think he has one any more. That certainly isn't to say that he doesn't or couldn't farm out machining projects to a shop. For that matter, that may have been the way he built my engine! ;D
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The question is it worth the $1350.00 for the conversion plus another $798.00 for the Weber carburetor setup (Bean also sells).
$1,350 seems a ridiculous price for 2 hours work in a machine shop and a cast manifold. Most cast manifolds retail around £120 + VAT which at post Brexit exchange rates equates to around $175.
Alex in Norfolk.
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Brian, that's the way I remember it.
Joe, is that current information from Bean? His website is WAY out of date. Regardless, I think it would at least be an interesting exercise to call them over at Bean and ask about it. Bean used to have a machine shop - he built my engine - but I don't think he has one any more. That certainly isn't to say that he doesn't or couldn't farm out machining projects to a shop. For that matter, that may have been the way he built my engine! ;D
I'm taking the information off Bean's website. I know it is very old so I would not be surprised if the prices have increased, assuming he still offers the modification. Alternatively there is always the conversion to SUs. And there is also a conversion to a Weber 38/38 downdraft. Both of those don't require modification to the head.
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If anyone in the USA is on speaking terms with Omnitec or Bean, and they would be kind enough to give them a ring to find out if they have any manifolds left, I need 7 inlet manifolds to convert all the Zenith heads I have accumulated here.
I can get the machining done locally, and the manifolds would only be gathering dust on a shelf somewhere.
Alex in Norfolk.
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Brian, that's the way I remember it.
Joe, is that current information from Bean? His website is WAY out of date. Regardless, I think it would at least be an interesting exercise to call them over at Bean and ask about it. Bean used to have a machine shop - he built my engine - but I don't think he has one any more. That certainly isn't to say that he doesn't or couldn't farm out machining projects to a shop. For that matter, that may have been the way he built my engine! ;D
I'm taking the information off Bean's website. I know it is very old so I would not be surprised if the prices have increased, assuming he still offers the modification. Alternatively there is always the conversion to SUs. And there is also a conversion to a Weber 38/38 downdraft. Both of those don't require modification to the head.
There is also the Mikuni HSR conversion to consider. I was seriously considering experimenting with a setup for my Hermes S2 with a single DCOE45. The setup should be similar to the Stromberg head for the twin cam.
http://www.v-performance.com/products/air_fuel.html
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Apparently you don't need to weld the cast alloy, it is more like soldering using an aluminium filler rod, and oxy-acetylene to heat up the surfaces and melt the rod.
But if a bolt on manifold is cheap enough, it cannot take long to cut off the old manifold, machine the head flat using a milling machine, drill and tap 8 holes, and put liquid gasket in place to seal the joint.
Alex in Norfolk.
Hmm, not sure about the soldering process on this application. My memory is hazy but I recall being able to join aluminium using a zinc based solder, I think it was a tin-zinc alloy similar to what we used to solder titanium sheet for Chlorine cells. It's a good bond but nowhere near as strong as a conventional weld and given the weight of the webers hanging off it I'd want a large surface area of bond before I'd go that way.
Bolt on looks the way to go to me.
Brian
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BDA wrote "but I wonder if the engine has gotten too old for many people to want such a high dollar mod"
Twin Cam Lotus engines are heavily used in various vintage racing applications. There is a whole industry built up around their manufacture, maintenance and performance upgrading. See the summer 2015 issue of "Historic Racing Technology".
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4129 wrote " it cannot take long to cut off the old manifold, machine the head flat using a milling machine, drill and tap 8 holes, and put liquid gasket in place to seal the joint"
But "where" to cut the head? Where to machine? What other mods may be required for it all to work: a spot of weld here or there, plug this passage, open up that one? And the spacial jigs required to make the whole operation easily repeatable. It's a lot more involved than it appears.
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It always distresses me when someone pours hundreds of hours developing a really useful modification and people cry foul because they have to pay more than the equivalent weight of scrap aluminium. All I can say is thank goodness for those of us who are not only willing but delighted to pay the prices required to support and continue these developments.
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If anyone in the USA is on speaking terms with Omnitec or Bean, and they would be kind enough to give them a ring to find out if they have any manifolds left, I need 7 inlet manifolds to convert all the Zenith heads I have accumulated here.
I can get the machining done locally, and the manifolds would only be gathering dust on a shelf somewhere.
Alex in Norfolk.
I talked to Ken at DBE the other day on another matter and asked if they still offered the Weber conversion. According to Ken, they no longer do the conversions and don't have any manifolds left. They refer customers to Omnitech instead.
Instead of casting new inlet manifolds, I wonder if you can adapt an existing aftermarket Weber manifold (cut and weld )to suit.
I plan on following up on this with my machinist next week and get his input on labor and cost for the conversion. I'm pretty confident that he's capable of doing the job. The problem again is sourcing the manifolds.
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So far, I have cut the manifold to 3 & 4 cylinders back flush with the head for an easy fit for a manifold. 1&2 cylinders will need milling to get a flat surface to bolt a manifold to. I go to my local tool shop tomorrow to see if the cut down manifold head will fit in their milling machine.
To cut back the manifolds, I used an enormous cut off machine I bought 15 years ago which has been sitting in my garage gathering dust. So far it has blown 2 x 13 amp fuses, but it cuts through the cast aluminium easily with the metal blade. I had to cut back the bottom of the guard to the blade by about 40mm to clear the head, but the remainder of the guard makes the machine quite safe to use.
Two options for a manifold. Steel plates connected by appropriate tubes, or get a specialist to cast one in aluminium. I prefer the aluminium route, as it will be easier to match up the ports and polish the insides, but it could be expensive, even for the 7 manifolds I need.
Alex in Norfolk.
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Very gutsy and interesting project! Good luck and please keep us up to date on it!
:lotus:
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How about posting a picture of where you're up to Alex ?
On the steel manifold option, I made one several years ago for a Volvo engine by exactly the same route you mention; 3/8" steel plate for the flanges and steel pipe between them. I think I even used 90 deg fittings suitably hacked about for some parts. All much easier than it sounds although making it look nice was a harder job.
But in your case it could make sense because should you decide to go for a cast manifold, you'll have a prototype all ready for them to see and perhaps use as a basis for a mold.
Another option whilst you're in the thinking stages, ever thought about converting one to throttle bodies or similar fuel injection ? A few guys on Lotuselan.net have fuel injection systems and it does seem an alternative way to go if you're cutting metal ?
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I am taking photos of the head as I go. I will reduce them in file size and post them during the week.
I also took photos of 4688R before the bodyshell went on a wooden pallet trolley to the ex-Lotus bodyshop for repair and painting. I screwed 2 4ft lengths of 4x2 to a pallet which came over in the 40ft container, and screwed on 4 trolley wheels, 1 to each corner. Then I used rachet straps to hold it down on the trolley. The whole shell weight not a lot, and can be pushed around a flat surface very easily. I saw the Formula 1 pit crews pushing the cars around on those trolleys, so I thought I would do the same.
To put the shell on the trolley, I cut 4x2 to put through the engine bay where the tanks were, and lifted the back with an engine crane, then used 2 metal trestles or bandstands, put an 8ft length of 4x2 side to side, and then chained the 4x2 from the bodyshell to the 4x2 on the trestles. Then I repeated the whole thing on the front, so the whole shell was held on 2 x 8ft lengths of 4x2, and the trolley went underneath, I lowered the shell onto the pallet, strapped it down, and pushed it on to my trailer to take it to the body shop.
Dave Golding, one of the two who run the bodyshop place, used to make the doors for Europas. He told me he made 6 doors a day, and more than half of the total made.
The problem I forsee in making the manifold is that the tubes taper in size from the 45mm down to around 40mm where they will bolt to the head. The valve seats seem to be 36mm, so the inlet tube further reduces in size during the last 75mm or so from where the manifold joins the head, to the valve.
I am thinking of either finding another cast aluminium inlet manifold of similar tube sizes and adapting that, or buying a solid 55mm diameter aluminium bar, and boring a 40mm hole down the middle, and then gas flowing it from 45mm down to the 40mm using an internal grinder.
It looks very do-able, once you have found the recipe. If the manifold and head are properly gas flowed, and the Webers properly jetted, I cannot see why 125bhp - 130bhp would not be easily available from a very tractable engine, for not a lot of expense. I forsee the actual machining of the head will take about 4 hours (1 hour with the grinder cut off tool and 3 hours with a milling machine).
My car (4129R) with its new Weber head, new cams etc cost a fortune to build the engine, but the car pulls to 6500 in 1st to 4th very quickly.
As I have around 8-12 weeks to wait until 4688R returns from the bodyshop in Lagoon Blue, I have time on my hands to experiment with the heads, as I have no more space left to strip down the 3 other TCS that I have waiting in the queue.
Alex in Norfolk.
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Well I have invested in a decent accurate milling & drilling machine, and I have cut into 3 & 4 cylinder inlet manifolds as far as the 80mm long milling bit will go.
I am about 25-30mm short of cutting back enough to get a proper fixing around the inlet port, so I will go online to find a longer milling machine cutter bit.
It is like drilling for oil, hoping that you don't find oil !!!
I will post photos soon.
Luckily I had a Zenith head with no cam bearing caps which was therefore worthless, so there is nothing to be lost by exploration.
Alex in Norfolk.
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Well I have invested in a decent accurate milling & drilling machine
Oh, that's interesting Alex, what did you get ? I've often thought that a milling machine would come in handy but never gone past the "wishful thinking" stage.
Brian
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I'm very interested in your progress as well! I consider it a pretty brave undertaking even if you have a "junk" head to explore on! :)
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https://www.machinemart.co.uk/p/cl-cmd300-mill-drill/
It seems to be able to do what I want.
It can only handle small items, but I have found a way of getting to where I want to cut, and it is very accurate.
Alex in Norfolk.
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When I read this thread, I thought "hmmm' that's a idea. I bought a mill earlier this year, and have a TCS engine sitting in the shop. After looking at the head, seeing how much material will have to be removed, and not knowing whats under the surface, said 'hmmm' again, went back into the house
Alex, I admire your taking on this project. Getting the head set up, and removing the substantial amount of material that needs to be removed, you will be turning cranks on that table quite a bit!
Please do post photos. And if you can, photos of how you set up the head to table. I'm just guessing you used a slotted angle plate?
BTW, nice mill. They really do come in handy!
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QED carries cam bearing caps. You would have to line bore them, of course.
http://qedmotorsport.co.uk/qed-shop/lotus-twin-cam/cylinder-head-components
Weber, Dell, Mikuni, Solex carbs flow way better than their period competition, absolutely, but, they have primary and secondary venturis which limit flow quite a bit compared to throttle body injection or, cheaper and easier to tune, modern flat-slide motorcycle carbs. I don't think you would have any problems hitting your horse power targets with a two port TC head and flat slides.
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Just a thought, plastic manifold? May be worth looking at. There may even be a 3D printing technic that could do it? Temperature stability and strength are the issues. It may even be possible to make up something that joins onto the cut off inlet stumps.
Dave
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Two options for a manifold. Steel plates connected by appropriate tubes, or get a specialist to cast one in aluminium. I prefer the aluminium route, as it will be easier to match up the ports and polish the insides, but it could be expensive, even for the 7 manifolds I need.
Alex in Norfolk.
Alex, just curious why you are building up 7 heads/manifolds? Do you have 7 Europa's or are they spares for a race car? Cheers, John
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Two options for a manifold. Steel plates connected by appropriate tubes, or get a specialist to cast one in aluminium. I prefer the aluminium route, as it will be easier to match up the ports and polish the insides, but it could be expensive, even for the 7 manifolds I need.
Alex in Norfolk.
Alex, just curious why you are building up 7 heads/manifolds? Do you have 7 Europa's or are they spares for a race car? Cheers, John
I actually do have 7 Europas which all had Zenith Stromberg heads. 2520R, 3089R, 3755R, 4129R, 4259R, 4483R and 4688R.
6 of them were basket cases requiring complete renovation with 3089R being very rusty and 4688R having a bad front end shunt, with a new chassis, and really awful paintwork. All 7 will be converted to RHD, and if I can find the right recipe, 45DCOE Webers.
Alex in Norfolk.
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https://www.machinemart.co.uk/p/cl-cmd300-mill-drill/
It seems to be able to do what I want.
It can only handle small items, but I have found a way of getting to where I want to cut, and it is very accurate.
Alex in Norfolk.
Thanks for the info and link Alex.
If you can do a cylinder head on that then I can't think of anything else I would ever do that's larger. I'm quite impressed, the last time I got as far as actually looking at prices they were more much expensive than that. Could be a winter project there.....
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I hope these are just small enough in file size.
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It's amazing what you can do when you put your mind to it. From the Machine Mart link you'd never imagine you could do something so complex on that miller, oh, I can see where the next share dividends are going !
It looks as if there's still a fair bit of machining to do at the back of the head, I wonder if that's a solid lump ?
Great pictures and invaluable for anyone else considering the same route. I've never seen anyone DIY this sort of thing before, well done mate !
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The pictures came out great! It looks like you're on your way! Good luck and keep those pictures coming!
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I have found someone who will cast the manifolds.
It is nowhere near as expensive as I thought.
If anyone else is thinking of going down this path, please let me know so we can see the numbers involved.
They say drilling into a waterway is no problem, just Loctite the studs in place.
I am thinking that the rubber O ring and metal sandwich plates are the best way of sealing the manifold to the head.
I am now waiting for a longer milling cutter/reamer to arrive from Hong Kong so I can proceed with flattening 1 & 2 ports.
Alex in Norfolk.
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Alex,
Quite the project!
Thanks for posting photos of the head secured to the mill table.
Work holding has taken a new meaning to me since I sent a piece of 2" stainless pipe zinging across the shop.
Are you using a end mill or roughing mill in the Jacobs chuck?
Andyh
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It is an end mill but it cuts through the cast ally sideways about 8-10mm at a time.
I hope the newly ordered 160mm long cutter from Hong Hong will be able to get to the lower bits.
Alex in Norfolk.
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Alex,
Good work so far, impressive. Be interested how you get on with the aluminium cast inlet manifold if you say it is not too expensive.
Dave
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I have found someone who will cast the manifolds.
It is nowhere near as expensive as I thought.
If anyone else is thinking of going down this path, please let me know so we can see the numbers involved.
They say drilling into a waterway is no problem, just Loctite the studs in place.
I am thinking that the rubber O ring and metal sandwich plates are the best way of sealing the manifold to the head.
I am now waiting for a longer milling cutter/reamer to arrive from Hong Kong so I can proceed with flattening 1 & 2 ports.
Alex in Norfolk.
Alex, I'll be talking to my machinist later on this week to get his thoughts on the conversion so consider me tentatively interested in possibly two sets of manifolds (for two heads).
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Alex, you're wrong about Elans. Almost all in UK are Weber heads. Only a short production of the S4 were Stromberg, then Weber and later Dell'Orto on Sprints and plus 2s.
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It seems it is best to carve off as much of the cast alloy inlet manifold as possible with a disc before using a milling machine.
The cutter is only 85mm long and cannot reach the lower bits of 3 & 4 cylinders.
I bought a long reamer but that just shakes a lot, works loose in the chuck, and falls out regularly.
I go in search of a 160mm long end cutter tomorrow at a specialist milling supply shop.
When I get the cutter on to the cast ally, you have to nibble off a small bit at a time (1.0mm -1.5mm) or the ally overheats at wraps itself around and sticks to the cutter shaft, needing a hammer and screwdriver to bash off before continuing.
The R&D continues. When I have the right length cutting bit, and the right cutting method, it should be much easier.
Now on to the manifold replacement scenario.
Turbosport of Bedfordshire quoted me £1,500 + VAT to make up the mould, and £30 + VAT for each casting, and £30 + VAT to machine each casting (faces flat, 16 holes drilled and 8 tapped).
A cast ally inlet manifold is one route to follow. The other way is ally plate and tube, carefully cut and welded. I now have the plate (3/8" x 4", they measure it in inches still) , I have the tube 50mm ext diameter with a 38mm hole.
Now the technical bit.
In 1970, I helped for a very short while, to prepare a Mini Cooper S for the 1970 RAC International Rally. It had an 8 port crossflow head with 4 Amal carbs, which cost an arm and a leg. Therefore I must assume that 4 separate inlet ports are potentially better than 2 siamesed inlet ports. The airflow must be much better.
Looking at it from a geometrical point of view, the 175 Strombergs have a cross sectional area of pi times (1.75 x 25.4/2) squared, or pi times 494.17 sq mm
The Webers have a cross sectional area of either pi times 36/2 x 36/2 for 36 mm chokes or pi times 38/2 x 38/2 for 38mm chokes, both times two, as there are two chokes per 45DCOE. That equates to 648 pi or 722 pi.
So 494.17 pi for Z/S versus 648 pi for 36s or 722 pi for 38s.
It seems apart from the Y branch on the siamesed inlet ports, the twin 45DCOEs potentially let in a lot more air than the twin Z/Strombergs.
Are you with my logic so far, and do you agree with this logic?
Second question:-
If the chokes in the 45DCOE are 38s (for maximum airflow for say a 145bhp potential power level), or 36s (for a 125 bhp potential power level), what diameter should the inlet tubes be for maximum airflow?
I have bought 38mm ally tubes on the basis that if the air has been restricted to a 38mm hole in the 45DCOE choke, what is the point of a bigger tube? Plus the valve seats in the combustion chamber look like 34mm.
Is the 36mm or 38mm choke tube in the 45DCOE deliberately smaller to allow a pressure drop when it increases to 45mm as it exits the carb, to allow the fuel to get sucked into the inlet airflow?
A manifold made from plate and tube welded together is alreadt very smooth all over, so minimal machining and minimal gas flowing required.
Constructive discussion please.
Alex in Norfolk.
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https://en.wikipedia.org/wiki/Cylinder_head_porting
Gas flowing looks like a job for the experienced.
Alex in Norfolk.
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"Is the 36mm or 38mm choke tube in the 45DCOE deliberately smaller to allow a pressure drop when it increases to 45mm as it exits the carb, to allow the fuel to get sucked into the inlet airflow?"
Yes, that's it exactly. Air flow increases as the passage narrows at the venturi. This creates a pressure drop which is used to draw fuel in.
A 45DCOE bolts to a manifold with 45mm wide ports. The ports taper down to x% where they join the head, also at x% and further taper to valve seat width. And, yes, there is a crap load of science and experimentation in shaping ports.
As to the Webers flowing more air, direct comparisons can be misleading. For instance the Weber also has auxiliary venturis in there as well while the Stroms do not. Not arguing in favour of the Stroms mind, they have running issues that arise from the use of siamese ports.
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So a gradual taper from 45mm down to about 34mm from the flange where the DCOE bolts on to the manifold to the valve seat.
As the manifold is accessible from both ends, and as the ports in the head are now much shorter, that should be easier than normal to achieve.
Alex in Norfolk.
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For the little I know, I think your logic is pretty good. I know that there are more choices for weber chokes than you mentioned and a weber throat is not completely open as there is an auxiliary venturi but for round numbers I guess you can ignore it. However as Alex and John have said, porting heads and intake runners is something for the experienced.
If this is an experimental project to expand your knowledge or just have fun at or it is something you might try to market (if it works out), I'd say, go for it. Otherwise, it sounds like you're getting to a cost level that is a significant portion of one that you can assume is right off the self and you haven't factored a development effort. That being the case, the "off the shelf" option would make more sense from a financial point of view.
But then when we're talking about your motivation, I'm probably not telling you anything you haven't already thought about.
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Question, why 45DCOEs not 40DCOE. If you are going for 150 bhp or less 40s are fine and will perform better lower down the rev range.
Dave
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Question, why 45DCOEs not 40DCOE. If you are going for 150 bhp or less 40s are fine and will perform better lower down the rev range.
Dave
Max possible choke for a 40DCOE is 36mm. I have 38mm chokes in my 145BHP engine as suppied by Quorn who did all the head work.
45DCOEs have "future tuning" possibility, 40DCOEs are limited.
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45's verses 40's always an interesting discussion. Richard Winter says he gets 150 with 40's and 32mm chokes and a very tractable motor. I have 40's with 34mm chokes, the largest size chokes for historic racing production class. I think 40's will get you to up to 170ish on bhp but the limitations are the head gas flow work, and the use of steel crank etc.
I question how tractable 45's would be low down, compared to 40's. run ok but not the best.
On inlet manifolds have you looked at off the shelf one's and converting? the crossflow manifolds for twin side drafts may be worth a look at with an adaptor plate and save a lot of grief. I suspect close but not Carling! I think the stromberg head port direction will be offset too much but would be easy to measure up to check
Dave
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45's verses 40's always an interesting discussion. Richard Winter says he gets 150 with 40's and 32mm chokes and a very tractable motor. I have 40's with 34mm chokes, the largest size chokes for historic racing production class. I think 40's will get you to up to 170ish on bhp but the limitations are the head gas flow work, and the use of steel crank etc.
I question how tractable 45's would be low down, compared to 40's. run ok but not the best.
Interesting comment there from Richard Winter, it ties up with my (hazy) knowledge on the topic. I have the old "Tuning Twin Cams" book by Dave Vizard and his comments were that it wasn't worth changing from DCOE40's until you were north of 155bhp.
I think you're right on the low speed running aspect with 45's, I could imagine the air velocity being significantly lower through a 36mm choke than a 33mm one and maybe not getting as good atomisation. Perhaps that's how Richard gets his 150bhp and tractability, by retaining the smallest choke practical for the top end power ?
SidedraftCentral on Yahoo groups is the place to go for weber tuning, the guys there lose me very easily !
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I have both 40s and 45s, so I will try both to see which gives better low down tractability, and if this affects top end power 5500-6500.
I can see the argument for both scenarios, which is similar to the 8 valve versus 16 valve head argument.
Specialist milling shop was useless, so the hunt for a 160mm long end on cutter continues.
I bought a 6ft length of 3/8" x 4" ally to make the carb end of the manifolds. Cost £40 and it should make 5 ends. So cost of ally for 1 manifold is likely to be in the region of £25 + welding + gas flowing. Just bought a pair of 40 DCOEs for £250 which will need cleaning and jetting, so costs look like around £350 plus the machining time/cost for head adaption.
Alex in Norfolk.
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Not wishing to drift too far off topic, by coincidence Kieth Franke has just posted a message on Sidedraft Central about getting 181bhp from an Elan TC engine with DCOE40's at 7000rpm. It's not a 1558 engine but 1700cc and with a later head, but the principle illustrates just how much you can get through a dcoe40. I suspect this has Kieth's own design of jets, which do seem to be an improvement on OEM Weber parts.
Back on topic, I see there are hiccups on the machining front. The chances of me being able to suggest a way forward are minimal but I'd like to see a photo of where you are and what the issue is when you've got a moment ?
Brian
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Alex -
concerning the cutter chattering and coming loose in the chuck - have you tried using a collet? some wd40/lube on the cutter may help with the buildup.
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I have bought a different chuck which takes up to 16mm diameter cutters. It has collets to grip the shaft of the cutter, rather than the 3 moving thingies on a standard drill chuck tightened with the gear key thingy.
Tomorrow morning, Cromwell Tools will have a 150mm long end cutting mill bit at their Norwich branch for me, which has a 16mm shaft. So by the time I get home, progress on milling starts around midday.
Meanwhile a replacement MGB fuel gauge sender for about £20 has arrived but the arm is too short. Otherwise identical, so I have to try to get the longer arm off the old sender, and put it on the new sender. 1/2" UNF bolts have arrived to plug the drain holes in the tanks, so I can continue restoring a pair of rusty tanks, full of sh1t. I think chipmunks have been nesting in the left tank. Luckily, access with the gauge sender removed is much easier.
Photos of progress this weekend to follow.
Alex in Norfolk (about a 90 minute drive from Brian in Lincs !).
P.S. Changing the arm on the fuel tank sensor is very easy. Bend 3 retaining tabs up, remove cover and spring, remove float from arm, change arms, replace spring, replace cover, bend back 3 tabs, replace float in shepherds crook on end of arm, job done.
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Here are the progressing photos of milling #3 & 4 inlet ports to get a large flat plate to bolt a flange to.
Two holes appeared. I was a little concerned that I had cut into the waterways. The last photo shows the holes from the other side. Easily welded or plugged up from either side.
Next task, make up 4 x head to manifold plates based on standard gaskets in the head gasket set. Then make up the one piece manifold to 40 DCOE plate from 4" x 3/8" ally plate.
Alex in Norfolk.
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I have started making up the manifold plates/flanges, to see fixings to the head, using a standard gasket.
1 & 2 cylinders were fairly straight forward, using a 60 degree slant on the studs.
3 & 4 cylinders were more difficult. A 60 degree hole struck the hole where the valve spring goes, so I am drilling 90/270, rather than 60/240. I have hit a waterway, but there is sufficient metal to tap a thread with 6 turns +.
Cutting the 32 and 40mm holes for the flanges is proving a challenge. I have found a decent type of cutter, and with 10mm ally plate, you have to cut from both sides, as the cutting blades quickly fill up with cut swarf.
I have ground the end off a tap to make the 5/16th UNC threads in blind holes. I am assuming 6 complete turns is enough stud in the head.
Next, I continue making the flanges, and make the stud holes flat. I will have to mill and pack with a washer to get the surface of the stud hole in the same plane as the inlet port.
The Weber flange I am copying from a manifold I cut up, placed on a 10mm ally plate, sprayed with black paint, and now I am cutting the black bits to get the right shape.
Alex in Norfolk.
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You're making great progress! Congratulations!
Six turns of a screw should get you most of the possible strength of the joint. A thread insert like a helicoil or timesert would be better.
I'm not a machinist and I they may not work in your situation and it may not help since you've already ground a tap, but they make bottom taps to get threads at the bottom of a hole - basically what you made yourself.
This is getting exciting!
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I think the 90/270 studs on 1 & 2 may not offer enough support to the Webers vibrating, so I will make the flange for the 90/270 lower below the port so that it will stop vibration snapping off the weld or straining the studs too much. This would also need a bigger gasket.
I will explore drilling and tapping a hole at 180.
The 60/240 studs do offer greater stability for up and down vibration on the studs.
Alex in Norfolk.
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Cutting the 32 and 40mm holes for the flanges is proving a challenge. I have found a decent type of cutter, and with 10mm ally plate, you have to cut from both sides, as the cutting blades quickly fill up with cut swarf.
If you are using a hole cutter in a drill to make these holes, then it's similar to what I was doing recently with steel. I picked a tip up from Youtube to prevent swarf build up. What you do is start off the hole and then drill another hole, say 9mm or so, at the edge of the circumference. That broke up the circle and although not perfect for me it did slow down the swarf build up.
https://www.youtube.com/watch?v=jTj8JVWDV6Q (https://www.youtube.com/watch?v=jTj8JVWDV6Q)
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Proper cutting fluid helps. I also found the incomplete circle makes it much easier, but with a decent cutter, it is quite quick. 5 mins maximum for a 40mm hole, even with changing sides so 5mm from each side.
32, 33, & 35mm cutters on order.
I will be using 5/16 stainless bar for the studs, then only thread them enough so they tighten before they run out of threaded hole. Not sure which type of Loctite for S/S to ally.
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So far, I have cut back the head Z/S ports to the main head block, made 8 holes for the 4 pairs of studs to attach the new manifold, made lots of prototype flanges with 32mm holes to attach the manifold to the head, made a 4 x 40mm hole 10mm thick ally flange to attach the 2 x 40 DCOEs, and now I am playing with my new lathe trying to make 4 x tapered tubes from 40mm to 32, to go between the Weber and the head flanges.
Cutting the tapered tubes on the lathe is only a challenge because I cannot yet find the right internal cutting tool to put in the lathe. Several ordered on eBay should be delivered for this weekend.
For a timing point of view, I reckon it takes 6 hours to machine the head and drill and tap the 8 stud holes, about 2 hours to make the 4 hole Weber flange, about 2 hours to make the 4 head flanges, about 4 hours to make the 4 tubes, and then the tubes need to be welded to the flanges on a jig, and then the ports and inlet tubes polished.
Total cost about £50 for the ally tube and plate, probably £100 for the polishing, about £50 for the welding, and a minimum 10 hours with the milling, drilling and lathe machine.
I am worried that the 1 & 2 ports will not match the 3 & 4 ports for air flow, due to the angles of the ports cast into the head, and the 2 40DCOEs will therefore need different jetting. Time alone will tell.
Is it worth it? Well, I either throw 7 Z/S heads away, sell them on eBay for not a lot, and but 7 Weber heads on eBay of varying quality and fault, or go down this route. Quite which is better, time alone will tell.
Will a 40 DCOE Federal head, with Federal cams, be much better than the Z/S head? I have no idea, but it should sound the part with the intake roar, and should be much easier to gas flow, and should have much more variation on the carb set up for various stages of tuning.
When the 4 tapered tubes are done, when I have the right internal cutting tool for the lathe, I will post photos of the parts ready for welding together.
Alex in Norfolk, with a garage full of ally swarf.
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I admire your gumption! Can't wait to see your pictures!
One of the great benefits to converting the Z/S head to a Weber head is that porting can be much more accurate since the intake runners are shorter and a porter would have much more control over the grinder throughout the length of the runner. It would be interesting to have your head ported by someone who is experienced with Weber heads when you're done so he could compare a traditional head with yours.
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It looks like you have left the breather box containing part of 3 and 4 inlets in place.
Why not cut the box off completely?
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It looks like you have left the breather box containing part of 3 and 4 inlets in place.
Why not cut the box off completely?
I think I will explore that route next to see what is involved, and how else to vent the breather which used to go into the air filter box.
Alex in Norfolk.
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Alex, I'm a little late in reading about your adventure but it seems that you are headed in the right direction.
I have some weber head photos that might be of use to you.
About two years ago I was asking a lot of questions (on Elan.net as I was rebuilding an Elan S1) about the twin cam weber head regarding the casting and where the water and oil ways were located exactly in the head as well as the thickness of the casting walls in certain areas. Couldn't get detailed enough answers so I sourced a used head that was no longer usable and had a machine shop cut it apart and mill away one area of the head. After media blasting and filing the entire head (knife edge sharpness where it was cut) I painted the water ways blue.
Here are the results:
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It is what lies in the square bit on the left of this photo which is the mystery.
I have Weber heads, so I know the dimensions of the inlet port tubes, but getting them even in size and shape, and to work properly with good air flow, is the challenge.
Plus getting the machining time down to an acceptable level, for both cutting away the Federal head, and making up the 5 flanges and the 4 tapered tubes.
Getting a cast manifold is only really economically feasible if large quantities are requires, and the casting would still need the flanges made flat by machining, the carb fixing stud holes drilled and threaded (5/16 UNC), and the port tubes gas flowed, so making up the manifold from 5 flanges and 4 tubes seems the easier and cheaper option at the moment. Welding it together will need a jig made to hold it in the right position while the parts are tacked together.
This is quite a challenge for someone who is used to working in wood rather than metal. Learning milling and lathe cutting techniques is interesting. The ally sticks to cutting tools and blades unless you frequently dip or coat them in cutting fluid, which seems a bit like gearbox oil.
I was using a hand held jig saw to cut the 4 hole carb flange to shape after cutting away as much with the 40mm hole cutter as possible. The jigsaw blade soon got clogged with molten ally until I frequently dripped cutting fluid on it, and then it cut through 10mm ally plate really quite quickly and accurately.
Hopefully the internal lathe tool is on its way so cutting the tapered tubes can continue.
Her indoors is getting a bit frosty, but at least she knows where I am; just follow the sound of 60's &70's music, and I will be close to the source drilling and milling away.
Alex in Norfolk.
P.S. thanks for the cutaway photos, they may be of help, but I think the Federal Z/S head is quite different, but only on the side I am cutting away.
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The cut away head is from the UK. I had it shipped to me in the US. I was just showing you exact locations of water and oil ways in the casting of a weber head. I don't know how different they may be on a stromberg head.
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Omnitech takes the breather box off completely. You should be able to see some of it in the video they have on their website. The last time I saw one of their converted heads it was already in the car (Elan) so all I could see was the top of the motor.
http://omnitech-engineering.com/category/automobile/engine_development (http://omnitech-engineering.com/category/automobile/engine_development)
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Thanks very much for that link.
Taking the box off reveals 3 strange extra holes. From the look at the manifold he has, it looks like he just blanks those holes off. I think 1 of those connects to the block with the strange rubber tube you get in the head gasket set.
The manifold has a complicated curve in its face. I wonder if that can be made into a straight line crease between the two planes.
I see much more ally swarf on the garage floor soon !
Alex in Norfolk.
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I started cutting away the breather box next to 3 & 4 inlet tubes.
First I started using a milling machine. It was far too slow, and all I succeeded in doing was wrecking 1 long milling cutter which cost me £60.
So I attacked the cast ally box with a small hand held angle grinder and a 3lb hammer. Much quicker.
Then all I have to do is smooth off the cut edges to give a flange to mount a flange plate on.
Without cutting back 3 & 4 inlet tubes to the same length as 1 & 2, I ended up with unbalanced inlet port tubes, and a bad K shaped change of direction on 3 & 4 which you could not rectify with any amount of porting or polishing. So, to make the inlet port tubes balanced for length, diameter, shape, and polishing, the vent box has to come off.
When the vent box is removed, you end up with the vent from the block which is normally connected to the head with a rubber tube, and a vent down from the cam cover area, with no connection to anything, so I am thinking on making a plastic T piece, and fittings to the block and underside of the cam cover area, and venting them into a catch tank if I am not using the standard inlet air filter to which the head vent is normally connected.
I will downsize photos and post soon.
Next I will screen capture the Omnitec photos to see where they mounted the studs to attach the manifold to the head, and start drilling holes for the same head stud fixings.
Alex in Norfolk.
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Photos of cutting off the breather box with an angle grinder.
I cut back the face too far cutting into the cam cover, so when I do this for real, I will have to face the head carefully about 5-6mm further out.
You can see after cutting off the breather box, the ports are the same length, the same shape, and very easy to polish.
The manifold plates and tapered tubes have been made up as a prototype to see feasibility. If all 4 tubes will be the same length and all point in the same direction, the manifold may be easy to cast up. I will make 4 long tapered tubes and a decent flange to attach to the head, and see if the cast head is easy to produce.
Alex in Norfolk.
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Great stuff, Alex!
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Wow!
This is very interesting. Thank you for photographing and sharing.
It appears with the right tools, this is a doable modification.
The tapered intakes look great.
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You need a compound lathe to taper. The bit moves at an angle of 3' for the long tubes, and 5' for the shorter tubes. I worked out the angles using a circular saw and cutting plywood to the right shapes. The circular saw has accurate calibrations so you know exactly the angle you are cutting to the nearest degree. It is very accurate.
You have to taper the insides of the tubes first, as the lathe chuck cannot hold the tapered outside end.
Once I have the right recipe, I will do most of the cutting myself and get a proper machine shop to do the final facing, as it is very difficult to get all 4 flange mounts in exactly the same plane without a very big milling machine or grinding machine.
I actually used the lathe to face 3 & 4 ports as the milling machine won't fit, it is too small. I put the milling bit in the chuck of the lathe, and moved the whole cylinder head at right angles to the cutter as the cutter rotated.
I will get the hang of it all soon.
Cutting the tapered tubes is actually very quick providing you get the tube exactly square in the chuck. I rotate the chuck by hand to see if there is any wobble or run out before starting the lathe.
Alex in Norfolk.
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Was the integrated intake manifold originally a cost saving measure?
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Was the integrated intake manifold originally a cost saving measure?
I cannot see how making up molds for two different heads, the Z/S version and the Weber version, can be cost saving.
I would have thought making molds for two different bolt on cast ally manifolds would be a lot cheaper.
I cannot see any reason for making the carb flange and inlet manifold part of the head casting. It makes no sense to me at all.
Alex in Norfolk
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Was the integrated intake manifold originally a cost saving measure?
I cannot see how making up molds for two different heads, the Z/S version and the Weber version, can be cost saving.
I would have thought making molds for two different bolt on cast ally manifolds would be a lot cheaper.
I cannot see any reason for making the carb flange and inlet manifold part of the head casting. It makes no sense to me at all.
Alex in Norfolk
I suppose it depends on the circumstances at the time, remember Colin Chapman was supposedly famous for wanting to shed all possible weight and achieve minimum production costs so I'll guess he looked at all options.
A separate manifold would mean fitting studs, more machining operations, gaskets and assembly time plus marginal weight increases (this from a guy who allegedly said "why are you letting those washers go for a ride on my car ?" so if you were never planning to have anything other than webers on your car, there is a case for all-in-one.
Back in 1962/63 when setting out with the Elan it probably seemed logical to have a single casting, especially if he could flog them to Ford with an attraction of reduced assembly-line time. It's only much later when the US emissions kicked in (?) that he had to find an alternative to webers, and he did try to convert all Elans to stromberg heads around 1969-ish. If that had worked out ok with the UK market I doubt we'd ever have had dellorto equipped Europas, both the Elans & Europa would have ended their days with Strombergs and the same base casting.
With our 20/20 hindsight and knowing that Lotus would need to offer variations 7 years down the line it does make sense to have a head casting with separate manifolds, but back in 1963 I'll be the accountant vetoed it !
Brian
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The switch to Strombergs was for two reasons. Firstly for emissions, Stromberg would assist manufacturers meet emissions standards. Something Weber wouldn't do until years later. Second, the Stromberg heads with non-emission carbs put out the same power as the Weber heads for production tuned engines. Stromberg carbs were MUCH cheaper so, for a while, both Euro and Federal production engines came with Strombergs. The Euro market protested which led to the reintroduction to production cars of the Weber/Dell head.
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They only had to make moulds for the inlet manifolds, not the entire head. They always were separate moulds.
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After much machining of the cast inlet ports on the head, I have now come to a halt on R&D as I have hit 4 problems, 2 of which are considerable, and 1 of these is a deal breaker in my mind.
If I didn't cut off the breather box, 3 & 4 ports had a nasty K kink in them, so it had to come off.
The Problems:-
1) There is a iron plug in the head, which presumably plugs a waterway casting, which gets in the way of machining a flat surface. It will protrude about 1/2" proud of the flat surface. This can be overcome with making a round cut out in the flange which needs to be bolted to the head.
2) There is an oil breather from the head, and another breather from the block, which need to be linked and vented into the inlet air filter or a catch tank. So a plastic T piece needs to be fitted to the head when it is fitted to the block, similar to the existing rubber tube.
3) When cutting the head flat to get a completely flat surface on which to bolt the manifold, you cut in to the camshaft area in the top of the head. This could be solved by a 60' change in the plane of the flange to be bolted to the head which Omnitech did,, but this needs complicated machining to both the head, and to the flange to be bolted to the head.
4) I think this is the deal breaker. After machining the face of the head flat, and I was cutting 10 thou off a time until I got a flat surface, there is not sufficient meat left in the head casting to drill and tap holes for stud fittings. I was hoping for 6 full turns of the 5/16" UNC thread. I don't think I can find sufficient places where this depth in metal remains after machining the face of the head flat. I have drilled many holes into the head in suitable fixing places, but very few are now suitable.
I looked at the manifold Omnitech had bolted to the head, worked out where their holes were drilled, but there just was not enough meat there to cut 6 turns. With the shear force of the 2 x 40DCOEs wobbling up and down, you need decent a large number of fixings for the manifold to the head. I think 8 studs would be good, 6 a bare minimum, but I can only find about 3 decent fixing points, and these are all in a line in the middle of the inlet port, so not of sufficient top and bottom spacing to prevent shear from the inevitable carb wobble.
Therefore my research will stop unless I get some inspiration to solve these problems.
I have taken a photo of the 4 problems listed above, and will post mid week when I can reduce the file size of the photo.
My investment in time has been considerable, about 12-14 days so far, my investment in machinery has been a lathe £1200 with cutting bits, a milling machine about £750 with milling cutters, and a belt sander machine about £200 with the sander belts etc. I just hope I
find things to use these for to justify this expense. Well, as they say, nothing ventured, nothing gained, and if you don't try, you will always be wondering "what if".
My next challenge is to get the soda blaster working so I can clean up all the rusty and dirty parts easily. Cleaning cast ally is the challenge, so I will try to work out how to use the pressure blasting cabinet I have bought. I had to buy an extractor fan to join to the side to remove all the dust, as when you start blasting, you can see FA without extracting the dust.
Alex in Norfolk.
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You sound a bit down Alex, and to be honest I'd probably feel the same. But, as my old boss used to say "research isn't easy, if it was it wouldn't be research". Or something like that anyway.
There's going to be a way forward, it's just a case of finding it. Someone else has done this trick so it must be possible. Let's see some photos of where you've hit snags and maybe we'll have a lightbulb moment. I think you've done well so don't give up just yet.
Ideas, first thoughts and no doubt all to be discarded but maybe it will spark something else that will work.
You say the wall is too thin to take a stud, ok, one way out of that would be to cut say a 1/2" hole and then weld in a small (but thicker) plate for drilling/tapping. It will reduce the waterway behind it, but probably not enough to matter.
The other, and this might be ridiculous but I don't know until I see the area, is to overlay with weld to bring it up to thickness. So far I'm assuming your aim to get a flat surface has been by removing metal, maybe adding some is one way forwards. Aluminium is easily MIG welded and that can put a lot of metal down quickly, far more than the usual TIG approach.
This is too interesting a project to pack in just yet ! ;)
Brian
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I have coloured in the problem areas on the head. I will post photos soon when I can downsize.
Red are the holes with insufficient thickness.
Green are the holes with about 6 UNC thread depth.
Black is where I have broken into the cam chamber. Just welding a piece of 5mm x 5mm bar would sort that out.
White chalk is where the oil breather comes down from the head into the old vent box. Drilling a 15mm hole and sticking a tube in that would work easily.
Blue is 5 areas where I could weld 6mm or 10mm ally bar with already drilled and tapped bolt holes in it. they will be each side of the 4 ports, which seem very equally spaced.
Photos probably Monday evening. My other computer has photoshop elements on it which I use to downsize the photos.
Alex in Norfolk
P.S. I seem to have found another way of downsizing 3Mb photos.
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I have a better idea.
Make up identical flanges in 10mm ally plate, drill and tap 5/16" UNC threads, and weld the flange plates to the head using a jig to keep them in the exact correct position.
Then use the same jig as part of the jig to make the manifold for welding.
So the sandwich will be head, 10mm plate, gasket, 6mm plate, tapered tube, 10mm plate 40 DCOE.
I will make the flange plates and the jig next weekend to see if this is possible.
Alex in Norfolk.
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A single plate welded to the head will not be sealed "behind" the plate. You would have to weld multiple plates; and then machine them all to the same plane afterwards. There's a good reason Omnitech uses a CNC angled "cut" and you have found it.
Stock, there is not much to choose between the Stromberg and Weber euro set-ups though the Webers may be a little quicker revving. If it is power you are after, fitting flat-slide motorcycle carbs to your Stromberg heads will easily meet/exceed the air-flow capabilities of 40DCOEs, perhaps even ITBs. When the slide is fully raised there is virtually no restriction all.
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Hmm, I can see you've been having fun drilling holes !
As John says, a plate welded on top will have problems although not insurmountable. I'm struggling to envisage the geometry to some extent and that gives rise to concern about exactly how you'll get a plate welded over the 4 inlet holes. One snag will be the need to weld/seal the bores at the plate/head interface. It could be do-able but depends on the tig torch you have I suppose.
It's definitely blue sky stuff but looking at what you have makes me think of a weld overlay. Not practical with TIG welding but aluminium mig welds quite easily and although it would be expensive in terms of wire I could see 3-6mm of weld metal going down over the length of the head without too much problem and very quickly. That would give machining and tapping clearances without any snags that I can see and a solid base to work forwards from.
How deep are those red holes, would another 3mm give you sufficient thread ?
Brian
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Looking at the machining that Omnitech does compared to your head, it looks like they dont mill the inlet tracts completely flat. It looks like their intake manifold has a bit of the intake tract cut into the angled portion. I wonder if this keeps more material on the cylinder head. It also looks like they did the machining via CNC, the little bulges for the cam studs look untouched. I'm sure you could machine them off then build them back up with weld, but that involves welding.
I also do recall reading somewhere that the reason Omnitech didn't weld a manifold or a plate on was due to warpage when welding. Also, you would lose any heat treatment to the head.
Also, I had a thought about the stud engagement, could you machine up some blind threaded bosses and weld them into the head? Drill or machine out a pocket with a step, then weld in some top hat section bosses?
Rod
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So Plan B, to make up 10mm thick flanges, with 5/16" holes already tapped into them to take the studs, continues.
These flanges are to be welded to the head around their entire perimeter to give an airtight seal.
Technical Problem:-
The venturies in the 40DCOE are supposed to be 32mm diameter for standard state of tune.
The valve seats measure 34.4mm diameter at the combustion chamber.
Having machined the inlet tubes off the head to the first flat face available, the inlet ports at this place are 29.6mm diameter.
I made the holes in the flanges 32mm diameter.
Question:-
When I make up the flanges, and the inlet tubes for the manifold, the tubes start off at 40mm as that is the size of the carb at the flange. I reduced the tubes from 40mm down to 32mm by careful machining. When I get the ports gas flowed so the manifold and head match up properly, do I get the ports on the head where the manifold bolts on, increased in side to 32mm, 34mm, or leave them at around 30mm which is what they are.
If they stay at 30mm, I am going to have to make up another set of flanges and tubes, which is no big deal now that I have the tools and the method.
The heads will have standard Federal spec cams, I can get the compression increased slightly by planing the head, but otherwise, with just gas flowing, 40DCOEs correctly jetted, and a tubular exhaust manifold, I would class the engine as stage 1 tuned, and I would expect around 120-125 BHP.
Does anyone out there know about port sizes, or should I consult a Lotus Twin Cam head porting expert?
Alex in Norfolk
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Hi Alex,
I see what you meant in the other thread about metal on your workshop floor !
I'll be honest and say I have no idea what the answer is to the port diameter questions, all I can comment is that it's not always a case of opening everything up as wide as possible, sometimes the venturi effects come into play. But quite honestly I've no idea if it applies in this instance.
I know it's potentially dangerous to take measurements from drawings but there's a sectional elevation in the manual regarding valve guides and followers which might give a clue as to the OEM design. If you look it does change sections in a few places and I could convince myself that it's not the same diameter as the inlet valve. Take a look for yourself at the image.
But the bottom line is that for best results you need someone who knows what they're talking about, and that's not me I'm afraid. I think if I were doing this I'd try to measure a weber head along the inlet tracts and see how that compares with what you're trying to do. If you haven't a "spare" weber head in your collection, I've got one in my workshop that I can try and measure up for you with some inside calipers. It won't be 100% accurate but it'll give an idea of the shape.
Brian
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Just invested in David Vizard, tuning Twin Cam Fords to see if there are any clues there.
I think I will call in at QED and have a chat when I pick up my ally seats from Loughborough. Quorn is very close, about 4 miles away, and on my way home.
Logic would say that a smooth transition from 40 down to 34.4 would give the best gas flow. I think the venturi effect is only needed to pick up the fuel. I would have thought once the fuel and air were mixed in the carb, a smooth air flow would be all that was needed into the combustion chamber.
Alex in Norfolk.
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Just invested in David Vizard, tuning Twin Cam Fords to see if there are any clues there.
I think I will call in at QED and have a chat when I pick up my ally seats from Loughborough. Quorn is very close, about 4 miles away, and on my way home.
Logic would say that a smooth transition from 40 down to 34.4 would give the best gas flow. I think the venturi effect is only needed to pick up the fuel. I would have thought once the fuel and air were mixed in the carb, a smooth air flow would be all that was needed into the combustion chamber.
Alex in Norfolk.
The guys at QED sound like your best bet. In all honesty I'm just guessing, you really need someone who's had a TC on a flow rig. Didn't Dave Vizard do a lot of work on them before he moved onto more modern stuff ?
The only reason I mentioned venturi is that I remember reading something about widening ports with DIY gas-flowing and how the wider areas lost velocity and hence fuel dropped out. It's hazy, could have been in something like an old issue of Car & Car Conversions back in the day. I think the main message wasn't to re-shape or remove metal, just to blend in obstructions around the valve guides.
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So a gradual linear reduction from 40mm down to 34.4mm would seem not to drop any pressure, whereas 40 down to 29.6 and then back up to 34.4 would seem to drop pressure and possibly upset the fuel/air mix.
Until I know the size of the ports where the manifold meets the head, I cannot make the flanges accurately, I can just work on the rough prototype.
But it does seem very easy to get to the ports on the head, and the inlet manifold, which are quite short, so gas flowing to the correct diameter would seem to be simple.
Alex in Norfolk.
P.S. Hamilton must be itching to get racing to get full points for the race, and hoping Verstappen takes out Rosberg on the re-start.
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A good port narrows as it approaches the valve guide to increase mixture velocity and density. The port then opens up from there to the seat as there is now a valve stem in the middle of the port and a valve head to work around as the flow goes through the port. It "looks" wider but it's not really.
Porting is not intuitive or there would be no need for flow benches.
Welding individual flanges just on the outside may also be problematic as there may be voids and gaps formed where the flange touches the head. This will create swirls and eddies that will negatively affect mixture flow. Welding the flanges on the inside may be required though I'm not suggesting you do so. You need to talk to someone experienced with welding on TC heads specifically.
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The Federal camshafts are the type C, or SE spec.
The power you're expecting is around that of an Elan Sprint or Europa Special, which used D type camshafts, 40 DCOES and 10.5:1 CR.
You'll be somewhere around SE spec, or 115bhp or so, I imagine.
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P.S. Hamilton must be itching to get racing to get full points for the race, and hoping Verstappen takes out Rosberg on the re-start.
That was quite a race! I had the same thought as you, but I wouldn't be unhappy if Rosberg wins the championship. I think he deserves it. Verstappen is amazing! His run through the field after that stupid stop for tires reminded me of Senna at Donnington in the rain in '93. Lewis needs to watch out for him.
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(part quote)
So a gradual linear reduction from 40mm down to 34.4mm would seem not to drop any pressure, whereas 40 down to 29.6 and then back up to 34.4 would seem to drop pressure and possibly upset the fuel/air mix.
I don't think it's solely down to the diameters, my suspicion is that it's more about the available cross section for flow at any point. As John points out, once you're at the valve guide you have an intrusion into the fuel stream, both from the guide coming out of the inlet wall, the valve stem and valve head to get around. Although you measured 34.4 at the valve seats, you're not going to have Pi x r^2 area available because it's cluttered up with a valve.
The area available for fuel to get inside the combustion chamber is going to come from the valve diameter & amount of lift on the cam. I'd guess at the point the fuel passes the valve head it's going as fast as it ever does, which of course will help atomisation, etc. (well out of my depth now :) )
None of which helps you I suppose, all just speculation. The fact is you're in the position where you've just got to give it a go and refine as you move along and things strike you.
Brian
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Reading David Vizard's book, page 21:-
"It will be seen from Fig 9. that roughly speaking, the inlet port can be divided into three sections. The first part is tapered, the second is a parallel section. After this comes a short section which slightly flares out to the valve seat diameter. With the exception of forming the venturi and blending the tapered port section, we must avoid removing any more metal than is necessary to achieve a smoothly contoured port with a good finish."
I read this as match up the carb 40mm at the gasket joint to the start of the inlet port tube of the manifold, gently taper the port down to the diameter of the parallel section, and then slightly modify the larger bit just before the valve seat, which is best done by a specialist.
So I need to measure the diameter of the parallel bit, and make up the inlet manifold to taper evenly down to the smallest diameter of the port, and then give the head to a specialist gas flow chappie, who can smooth out the manifold and the inlet port on the head, and smooth out and enlarge the bit just before the valve seat.
It is 0'C outside, 32'F, so my enthusiasm to venture outside to start making up the manifold tubes is cooled substantially. There is international sport on the TV for the next 6 hours, cricket,India v England, then soccer Manchester United v Arsenal, then England v Fiji in Rugby. Decisions !!!
Alex in frosty Norfolk.
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G'd evening Alex, it was cold up North in Lincolnshire this morning as well, so I don't blame you for huddling round a warm TV !
I've got that book as well and I'd agree about matching the gasket to the manifold. I think all you're looking for at this stage is to remove any obstructions and try not to leave any "gaps" which might cause eddies and fuel drop-out. For the first prototype I don't think I'd do anything immediately behind the valve or even very much around the valve guide, I'd just try to get something that hangs webers on the side of the head and actually runs.
Then it might be worth having a shot on a dyno to see what sort of power it produces as a baseline before attempting any more work to gas flow the installation. If you can't get access to a dyno easily then maybe the stop-watch dyno will have to do, but at least then you'll be able to see the benefit from any additional work. Whereas if you just dive in and go for broke you won't know if the 140bhp ( :) fingers crossed ?) comes from your conversion or the gas-flowing stages ?
Brian
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Hi Alex. Practical Performance Car did a piece in the last couple of years pouring Latex into ports so that the internal port profile could be visualized. They then sliced this like a loaf to measure the cross sectional area as it changed through the port length, using the results to steer metal removal.
I can't remember the right progression in areas, I'm sure it's somewhere on the internet though.
Perhaps its worth doing that on a Weber and a Zenith head just to see what the differences are in this respect?
Really very interesting project and thread, enjoying watching your journey here. Hope you carry on beating your frustrations!
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Well the long R&D continues, with trying to make up flanges out of 10mm thick ally to weld to the head, and a manifold made from 6mm ally to bolt to the flanges, and 10mm ally where the 40 DCOEs bolt on, and 50mm ally tube with a 30mm hole to make the inlet port tubes.
Enclosed is the progress so far.
R&D has been a mixture of finding the right machines, getting the right tools to fit in the machines, cutting bits, hole borers and milling cutters, and getting used to using the machines to their capability. Add trying to work out how much metal you can cut off the inlet side of the head, and trying to get it all to work from a gas flow point of view, and you have an "interesting" learning curve.
I now need to get the angle of dangle right for the tubes, so I need to make up a jig to keep all the bits in the right place while they are tacked together for proper welding.
Once the manifold and head have been welded, the finer grinding and polishing of the head can take place.
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Any more progress on this conversion project?
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These people already have a casting. It isn't cheap though. https://www.ebay.com/itm/Lotus-Elan-Stromberg-Head-Conversion-for-Weber-Carburetor/401707452794?hash=item5d87a1497a:g:sywAAOSwcHRcZNpp
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Hi Alex,
I have not spoken to John in a while (he built my engine with the Webber conversion). His email is john@omnitech-engineering.com and his cell is 001 360 820 1333
Cheers,
Bart.
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I found it was much easier to find a second hand Weber head, but having said that, I am trying to find an engineering company to cut the inlet cam groove into the heads I bought, where the alternator pulley attaches.
Cutting back the head is a very specialist engineering project, so by the time you do that, make up the inlet manifold to attach, and weld it all together accurately, I can see where the cost comes from.
Alex in Norfolk.
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Literary, thanks for the info on Stromberg heads today! It was great to talk with you!
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:beerchug: Back Atcha Turbo. And BDA: Turbo used to live in Louisiana.
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Another displaced cajun, eh? Who knew?
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I am from all over as my Dad was in the Air Force and then I joined for two terms of enlistment as an aircraft machinist and welder (SR-71 was one of the planes at my base).
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I have just had a conversation with Scholar Engines of Suffolk about converting the Zenith Stromberg head to a Weber 40DCOE head, and left 3 Twin Cam heads with them to determine feasibility and conversion cost, a Zenith head, a Weber head, and the head I cut up to see what was needed.
Alan who knows a lot about Twin Cams says there is a demand for the conversion so is trying to see exactly how this can be done on an economic basis.
I will let you know what transpires.
If this is economically viable, it may well be worth updating on the Elan Forum, as I am sure the demand there is greater than for Europas.
I sent him this link.
https://www.youtube.com/watch?v=PL0kcA2shRk&t=32s&ab_channel=JohnMcCoy
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Does Omni-tech no longer convert stromberg heads?
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This side of the pond would not know, and the logistics of shipping would not make that an option.
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Many years ago I bought an Elan Weber head and had Dave Bean modify it to include the hole out the rear of the intake cam for the alternator drive. I use 40 DCOE’s. Worked out very well.
Tom
74 TCS - 4605 R
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Good news for anyone with a Stromberg head who wants to convert it to a Weber head.
I have been working with Scholar Engines of Suffolk England, and they have found a simple way of converting a Stromberg head to a Weber head economically.
They are still working on the prototype for me, but when I saw their idea yesterday, and how they intend to finish it, it looks very good, and very simple.
They are doing it for twin 40 DCOEs but exactly the same method would be used for twin 45 DCOEs.
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These people already have a casting. It isn't cheap though. https://www.ebay.com/itm/Lotus-Elan-Stromberg-Head-Conversion-for-Weber-Carburetor/401707452794?hash=item5d87a1497a:g:sywAAOSwcHRcZNpp
This is the route Scholar Engines are following. It seems to be economically viable.
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Not experienced in this myself but I have heard that welding twink heads can be challenging. Hope it works out though.
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Not experienced in this myself but I have heard that welding twink heads can be challenging. Hope it works out though.
Between the owner of Scholar (Greg I think), the previous owner who still works there, and the engineer who is actually doing the work, they seem to have heaps of experience, and confidence that they will turn out a strong good looking conversion, with the inlet ports all gas flowed properly, for a realistic price.
They had made a template to hold the cut manifold in situ to tack weld up in position. Next they will fill in all around the joint to make strong, then they gas flow, finally they finish the outside to make it look original.
I remember Scholar used to make Formula Ford engines in the 1970s. They take pride in what they do, the current owner has an Emira on order, and he knows Lotus quite well.
He said that Lotus want to get production of the Emira up to 7,000 per annum (about 30 a day). He thinks the Emira will be the last Lotus made in the UK. He knows all the faults of the Merc 2 litre engine they will put in soon, apparently developing up to 350 bhp. It overheats, and the oil stops, causing everything to seize up.
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Sad if the Emira is the last Brit-built Lotus. Lotus was the last independent Brit car company. I heard that the Emira is going to be the last Lotus with a gasoline engine.
Then on the other hand, if they put motors that overheat and seize up in the Emira…
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I've no doubt that they can and will do a decent job, as you say they've been around for years and if they've retained the same core workforce, well, it's slam dunk.
I think they might struggle on price though if they're making a casting whereas a fabricated add-on should be quite possible. I'd hope they take it a bit better than that photo in the Ebay advert though, it looks like two cylinders have elbows in the inlet tract and that can't be as good as the OEM design.
Having said that, they have loads of race experience and I expect they'll bench flow to prove their conversion is as good as a standard head. I'd bet they make a straight inlet and weld them individually into place ? Can't see any obvious problems with that.
He said that Lotus want to get production of the Emira up to 7,000 per annum (about 30 a day). He thinks the Emira will be the last Lotus made in the UK. He knows all the faults of the Merc 2 litre engine they will put in soon, apparently developing up to 350 bhp. It overheats, and the oil stops, causing everything to seize up.
30 a day ? :huh:
good luck with that....... have Lotus ever made anything at that rate ? IIRC the Elise was the best thing they've had in recent years and it's a cheaper/simpler market but still nowhere near those numbers.
I love the shape of the car but I can't see those sorts of production numbers at a £75k price and even at £60k for the entry level it's a tough ask. I wish them luck though and if they do get to those numbers, perhaps the Evoras will become "cheap as chips old bangers" and I can get one to play with !
Brian
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At last I got my Stromberg head back from Scholar Engines.
They used a Weber manifold they had lying around, and did an excellent "cut and shut" job on the ally inlet manifold.
The R&D cost a few quid. They are working out a cost for me for converting the other Z/S heads I have lying around in my garage. They made up a steel template to hold the manifold exactly in place while they tacked it in place to the cut down head.
I think they did an excellent job.
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I think they did a great job too! :beerchug:
I suspect it was less expensive than what Omnitech would charge (I first heard about the conversion from Dave Bean but I suspect he was fronting for Omnitech but I could be wrong). Bean and Omnitech had bolt on rather than welded on solutions. Dave Bean claimed that it was better because it didn't interfere with the heat treatment. I'm sure Scholar took that into account. I never figured out why the intake manifolds were cast into the head in the first place!
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Well, it was Chunky. So cost would be my first thought. Does the head have enough meat in the right places for bolting a manifold, if Lotus had tried that approach?
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There is apparently plenty. https://omnitech-engineering.com/category/automobile/photos-engine-development
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Just finished rebuilding the engine with the Zenith Stomberg head converted to Weber inlet manifold.
The engineering shop forgot to drill and tap the hole for the brass tube servo vacuum take-off.
The thread is 1/8" NPT (National Pipe Taper). My local tool shop had the tap, I took the alternator pulley wheel off, stuffed kitchen roll tissue in the inlet manifold, made sure the inlet valve was shut, drilled an 8.5mm hole, and the tap went straight in with a bit of WD40.
The brass vacuum take off union fitted perfectly. I thought that was mission impossible. Result.