Lotus Europa Community
Lotus Europa Forums => Technical Articles and DIY tools and tips => Topic started by: Bryan Boyle on Monday,March 07, 2022, 11:03:20 AM
-
Question:
Loose and block off the shaft openings (removing the levers and bits from the carbs to actuate)?
or
Keep?
(as an aside, before removing the carb stack this afternoon, measured the clearance from the adapter plate to the secondary body...there was NO gap; the thackery washers were torqued down tight. O-rings in the secondary body were hard as a rock (the front carb had orange RTV around the ring...uh, no. Not proper. Replace the damn o-ring, don't goop up with RTV. Damn DPOs.)
-
Mine had the secondary shafts and butterflies removed. It reduces impediments to airflow, and the shaft holes are probably easier to seal than the shafts.
Just my two cents. It's also been suggested to flip over the secondary manifold to produce a sort of Euro-style high balance tube manifold. But I haven't really evaluated that.
-
I suppose you could try to remove just the butterflies themselves if that is possible and keep the shaft in place but then the shaft holes could be source of air leakage past the shaft. It might be simpler to totally remove the entire secondary butterfly assembly.
Ken, thinking about your idea to flip over the inlet manifold to create a balance tube effect. I believe with the stock setup in place, and the butterflies closed, the air/fuel charge enters the bottom passage in front of the butterfly, and exits the inlet manifold into one of the crossover tubes over to the exhaust manifold back to the other crossover tube and back into the inlet manifold and exits behind the closed butterfly. Most owners just block off the crossover tube passages on the inlet manifold. Can somebody explain how a balance effect is created with the crossover pipes blocked off? I should probably look up the system in the manual.
Thinking it over, it appears that both passages connect internally maintaining the balance.
-
I still meant to remove the butterflies and shafts, and close off the crossover tube opening. With all of that done, I think the two carb throats are connected by a balance tube that runs along the bottom of the casting. So, rotating it 180 degrees would put the balance tube on the top. I haven't done this. I just read about it (probably here) and thought it would be worth looking into the next time I have the carbs off.
-
Mine had the secondary shafts and butterflies removed. It reduces impediments to airflow, and the shaft holes are probably easier to seal than the shafts.
Just my two cents. It's also been suggested to flip over the secondary manifold to produce a sort of Euro-style high balance tube manifold. But I haven't really evaluated that.
so what would be the advantage to that (besides eliminating perhaps a locus for the fuel to puddle (fwiw, the cross over tubes were deleted and the mounting flanges blocked off at some point in the hairy past on this car...).
-
You can flip the secondary manifold over but Stromberg mounting points are also flipped over causing the Strombergs to be mounted upside down. As you said, the down side of low balance passages is the pooling of fuel in the passages.
-
Which would mean flipping the plates that the strombergs are mounted to, also. wonder if that would work...IE would the intake line up...etc.
-
Of course...there is this which got me thinking...but may be too much carburetion for this engine, since it's set up for a TR6...but nice thing about webers is that they are almost infinitely changeable...lol.
-
That looks like an awful intake design...didn't someone on here have those and swap to Mikunis?
-
Would it be possible fill/block the lower holes in the secondary manifold in addition to removing the shafts and blocking those holes? ???
Then only the upper tube in the manifold is connected from side to side, just as you're requesting.
Or am I missing something (probably)?
-
Would it be possible fill/block the lower holes in the secondary manifold in addition to removing the shafts and blocking those holes? ???
Then only the upper tube in the manifold is connected from side to side, just as you're requesting.
Or am I missing something (probably)?
Nice seeing you again, Peter! Hope all is well! You know I post dense text when I'm working on a project, and this one is pushing the envelope for me in new directions...
Was just spitballing (poking a stick in the cage?). Have the intake down to the head flanges all apart...finding all sorts of DPO happiness (like no nuts on the 2 bottom studs holding both of the carbs on the adapter plate to the secondary throttle assembly), copious amounts of RTV squeezed out of joints, thackery washers torqued down tight, idle trim screws set vastly different between front and rear carbs, 2 different tapered needles (I have their mates in a box of spare parts...) in the pistons...So...back to 'stock' (except for the lack of secondary throttles) and set up per the book.
Have cleaned up the threads on the pile of 5/16x24 nuts, ran a die down all the studs to clean up those parts, have a stack of new split and flat washers to use where needed, new thackery washers, new gaskets, new diaphragms, new o-rings, new floats, new needle valve, a gallon can of carb dip and a couple parts brushes. Time to dig in, clean up, rebuild, and reinstall...
-
Would it be possible fill/block the lower holes in the secondary manifold in addition to removing the shafts and blocking those holes? ???
Then only the upper tube in the manifold is connected from side to side, just as you're requesting.
Or am I missing something (probably)?
Peter, it possible do just that. Blocking off the two bottom holes in the secondary manifold appears to just leave the upper passage and openings at the top of the manifold connected for balancing the two throats. The photo shows the back of the manifold with the upper return back to the manifold exiting at the top.
I'm starting to wonder if the the pooling of fuel in the low balance tube manifolds has some truth in it or it's just a potential problem that might happen. Most TCs back in the day and even now have the secondary butterflies removed and the cross over pipe opening sealed up. The upper and lower openings in the throat of the manifold were left open. Has anyone heard of these modified manifolds giving carburation problems due to pooling of gas in the lower passage and the symptoms? My TCS was left in that state for years and may be I was too ignorant to know I was having issues.
-
It's good to see you've also found this forum, Bryan. Things are going fine over here in Denmark, thank you. :D
The TwinCam will keep you occupied for a while. But I guess that was always the plan. :))
Time to dig in, clean up, rebuild, and reinstall...
While you are inside the Strombergs, remember to adjust the temperature compensators equally. Whether they are always shut or working is not so important, if they just work the same/balanced way on both carbs.
And consider having the plugs in the bottom of the fuel bowl welded. I assume your carbs are adjusted by the needle from the top, and eliminating 2 o-rings between the fuel bowls and the ignition parts below can't be a bad idea.
-
Peter, it possible do just that. Blocking off the two bottom holes in the secondary manifold appears to just leave the upper passage and openings at the top of the manifold connected for balancing the two throats. The photo shows the back of the manifold with the upper return back to the manifold exiting at the top.
The previous owner of my Europa had the secondary manifold replaced with the UK/Stromberg high balance tube manifold along with distributor and carbs updated to UK specs. So I never had one of these original secondary manifolds with butterflies and all. It really is an interesting contraption. :o
-
Those UK high balance tube manifolds are hard to find. I've been looking for one.
I thought the pooling of fuel problem in the US manifolds had to do with the manifold catching fire if there was a backfire or something, not that the pool caused variation in fuel/air ratios. It's all starting to sound like some legend whispered in the back rooms, than anything based in fact. (After that, I should probably go get my Nomex coveralls >:D)
-
Those UK high balance tube manifolds are hard to find. I've been looking for one.
I thought the pooling of fuel problem in the US manifolds had to do with the manifold catching fire if there was a backfire or something, not that the pool caused variation in fuel/air ratios. It's all starting to sound like some legend whispered in the back rooms, than anything based in fact. (After that, I should probably go get my Nomex coveralls >:D)
I'm thinking along the same lines; otherwise it would have surfaced a lot sooner than the 50 some odd years since these things hit the roads...Going to leave them unplugged; I think it's more important right now to set up the carbs per both the stromberg manual and the Lotus workshop books and go from there.
-
Just some random photos
#1...as removed. Neither carb had nuts on either of the bottom mounting studs.
#2...the secondary throttle body, sans the butterflies, and the adapter plates for the carbs cleaned up and the flanges (mostly) polished to present a good surface for the gasket.
#3...carb air chamber removed, will renew the diaphragms, and discovered the needles are the euro taper. I have the original spec taper needles...wondering which would be more appropriate for this area?
#4...the plugs made to seal the secondary throttle openings made from the shaft of the butterflies and will be secured with high-temp epoxy.
(yeah, I wish I had a parts washer and maybe an ultrasonic tank. Maybe in the next life...will clean up as best I can before reassembly. Maybe I should hold off on reassembly and bring the secondary body down to the airport, seal off the openings, and bead blast the shell. Buy a dunk can of carb cleaner and strip down to the bare bones and let the bodies soak? Nah...I'll just keep on doing what I'm doing.)
-
The pooling was associated with the low balance pipe manifolds fitted to UK Elans and Europas, not the US manifolds.
The high pipe was the cure.
-
The pooling was associated with the low balance pipe manifolds fitted to UK Elans and Europas, not the US manifolds.
The high pipe was the cure.
Thanks for the clarification! Going to leave well enough alone, and get things as back to stock as I can...and correct the DPO happiness.
-
Bryan, I like your reuse of the secondary shafts as plugs. Very Chapman!
When I got my car, back in 1989, and had to get it smogged, the needles and seats were worn enough I had to replace them. The old-Lotus mechanic I bought the car from recommended the Euro, floating needles. And all of that passed CA smog. (now it's grandfathered and I don't have to do that anymore)
-
Bryan, I like your reuse of the secondary shafts as plugs. Very Chapman!
Thanks for the compliment!
When I got my car, back in 1989, and had to get it smogged, the needles and seats were worn enough I had to replace them. The old-Lotus mechanic I bought the car from recommended the Euro, floating needles. And all of that passed CA smog. (now it's grandfathered and I don't have to do that anymore)
The needles in my car are the Euro taper, but whomever (and it wasn't the PO; going to start saying PPO, since the gent I bought the car from admitted that he was in over his head and was hoping someone like me would take it off his hands...) replaced them in the piston and never set the height correctly (there are a few other gotchas that I'm discovering...like 2" long idle adjust screws, which are just 6-32s but a case of the originals probably rolled off the bench, so the wrench just pulled something out of the parts box that fit..). Just taking my time, correcting the issues, using new rebuild kits (from Joe Curto), and setting up per the manual as the starting point.
Once that is done...on to mucking with the brakes. And, oh, yeah...got new throttle and choke cables. Thinking replacing them is going to be a goat rodeo...a lot easier when the lump is out of the car, but not there yet, so...
-
***DELETIA***
Have cleaned up the threads on the pile of 5/16x24 nuts, ran a die down all the studs to clean up those parts, have a stack of new split and flat washers to use where needed, new thackery washers, new gaskets, new diaphragms, new o-rings, new floats, new needle valve, a gallon can of carb dip and a couple parts brushes. Time to dig in, clean up, rebuild, and reinstall...
Finished first carb (rear carb...the front is almost there.) New gaskets where needed, temp compensator checked and they're close, need to find proper size drift to set the butterfly shaft seals, needles set correctly, float level set for 11/16", but for now...polished (I know, geeky) the top cap...and need to set the initial settings on the bench per the manual.
Waiting for the gaskets for the base of the secondary throttle block to the head, and have new viton o-rings to set the adapter plates at the proper clearance on the secondary with new thackery washers and have ALL the proper 5/16x24 nuts and washers at the ready. New teflon-lined throttle and choke cables coming...pretty sure that snaking the new cables will be a messy exercise...but needs be done. More as it happens, stay tuned. Headed towards seeing if I can get it started this weekend or next week.
-
Runs. Not sync'd yet. And idle is up around 1700 even with needles backed out...still work to do (new throttle cable, new choke cable...)
-
Well...got new cold start cable (it's not really a choke) in with zero issues (except for making another blood offering through the chassis access hole in the cockpit...). This is what I did...
1. Remove the inner cable from the new sheath (carefully...don't want to kink or start separating the strands at the cut end...), and put aside.
2. Remove the old cable assembly from the carbs and the mount under the armrest. Toss in the bin.
3. Push the new sheath in through the front mount, slip the lock washer and nut over the sheath, and thread the sheath through the backbone out the back, tighten the nut down on the cockpit side,
4. Go into the front of the engine room, making sure the cable misses the pulleys and belt, and gently pull the end up along the passenger (right) side. Now, the universal fit cable assembly that Ray sells is meant to be cut to length. So, keeping a nice sweeping arc out of the chassis bulkhead (and supporting it with an adel clamp set on the cross-tube where the catch can would normally be) down to the front carb. I used a dremel with a cut-off wheel to cut to length (using a set of dykes would crush the sheath), and then ran a needle file through the cut end to clean up any swarf.
5. Threaded the lightly lubed (I use LPS #2 from my days in an aircraft maintenance hangar...) inner cable through the sheath and out the other side in the engine room.
6. attach the cable to the clamp in the front carb, ensure the inner cable is pulled back all the way, and thread through the cable attach fitting on the cold start lever and tighten down the capture nut, leaving an inch or so past the fitting, again, using the dremel, cut off the excess inner cable.
7. Check operation. Pretty basic but still good to check that it works both all the way out (and the capture nut is tight) and all the way in. (Just a note, you never set a cable up so that when you push it all the way in, the knob bottoms out on the ferrule; leave a little gap so that the controlled lever is at its stop, not limited by the cable bottoming out. Just how I was taught when restringing control cables in airplanes...;))
Done. Now, on to the throttle cable. I'm thinking of leaving the existing sheath in place and just replacing the inner whilst lubing as I did with the cold start cable so I don't have to pull up the carpet on the driver side for now. I'm going to ruminate on it a bit.