Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: Bryan Boyle on Saturday,December 17, 2022, 11:57:07 AM
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I started pulling my spare head apart to make sure all was assembled properly (doesn't everyone have a spare head?). Glad I did, because, while the valve seats were redone (the engineer's blue to check valve seating is still apparent around the seats on the casting), it seems that the cam bearings were not changed (there is evidence of them being 'experienced'; the journals on the cam are fine, no marks, but there was no evidence of assembly lube when they were put back together.
This also leads me to think I should pop the valves and make sure the stems were lubed before assembly, too.
But one question: the seal on the input cam (they're D cams, for what it's worth) needs replacing...but I'm pretty sure the tool that's called out in the manual to put the new seal on has been many years lost to history, and I note that there is a split ring on the cam in between where the alternator pulley would sit (maybe a locating fitting?) and the seal.
For those who've done this...is that ring (easily?) removable so I can slide the new seal on? Or...is there some other method that's been used in the past.
(I've ordered a new set of bearing shells and have a tube of Graphogen to put it all back together...btw). Just want to get it right (without bunging up the new seal, which I have in hand).
Plan is to just swap heads (this one has been surfaced lightly and I checked with a straightedge; it's flat) when I pull the lump, but want to get it right so I'm not doing it a second time...
BB
3291R
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If the shop thought the head was going to be used, it would not be unusual to just lube everything with engine oil. As long as it doesn't sit too long, under a year, it works just fine.
Myself, I wouldn't be too concerned about the valve stems. If you are worried, just place the head upside down and use an oiler to put a drop or two of oil on each stem through its port and let it sit for a few hours.
The ring locates the cam pulley -- which is why you need to be careful not to over tighten its nut.
If you just push the seal on, the groove for the ring may damage the seal. You just need something "soft" for the seal to slide over this sharp spot. You could use electrical tape, heat shrink, thin plastic tube, etc. lube things up generously and fit it carefully.
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If the shop thought the head was going to be used, it would not be unusual to just lube everything with engine oil. As long as it doesn't sit too long, under a year, it works just fine.
Myself, I wouldn't be too concerned about the valve stems. If you are worried, just place the head upside down and use an oiler to put a drop or two of oil on each stem through its port and let it sit for a few hours.
The ring locates the cam pulley -- which is why you need to be careful not to over tighten its nut.
If you just push the seal on, the groove for the ring may damage the seal. You just need something "soft" for the seal to slide over this sharp spot. You could use electrical tape, heat shrink, thin plastic tube, etc. lube things up generously and fit it carefully.
This head obviously sat for a while in the shop. I disassembled the cams from the head and clipped off the old crumbling seal. A couple of the long studs are bent a little; the shorter ones are ok, so, will replace the 8 long studs, and use new nylocs all around when I go to put it all together. Not replacing hardware and consumables is false economy in my book.
The woodruff key is in the cam real tight...will pop it out later and remove the ring and use your idea of taping the shaft to slide the new seal on with generous lubing...and then put all back together. Like your idea about oiling valve stems though their ports, and will reassemble with graphogen or the ZDDP Paste (I've a tube of both) when I get to that stage. But, there were obvious wear marks on the shells, no scuffs or marks on the cam journals, so, thinking 'it's apart, just replace the shells" to forestall any issues down the road.
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Hi Bryan,
I've nothing really to add to what John's said, the cam seal is an easy fit and commonly available. I didn't need any special tools and from my notes the dimensions are ID 22mm, OD 34.5mm, 6mm wide if you have a local bearing supplier.
From your comments on worn cam shells & bent studs then I would be suspicious on the rebuild and want to check valve clearances before it goes back together. As the cams are off I'd also pop the followers out and make a note of the shims in there so if the clearances are wrong then you'll know what shims to get. It's much easier to do whilst the head is on the bench than leaning over into the engine bay.
If you don't already have a copy, one thing I would get is Miles Wilkin's book on the Twin Cam engine. It's been revised in the last few years for newer sealants but the main benefit is the number of photos as he takes you through a complete strip/rebuild and the comments along the way about the best way to do things. It's a bit like Brian Buckland's book on the Elan, written with the average DIYer in mind.
Brian
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Hi Bryan,
I've nothing really to add to what John's said, the cam seal is an easy fit and commonly available. I didn't need any special tools and from my notes the dimensions are ID 22mm, OD 34.5mm, 6mm wide if you have a local bearing supplier.
From your comments on worn cam shells & bent studs then I would be suspicious on the rebuild and want to check valve clearances before it goes back together. As the cams are off I'd also pop the followers out and make a note of the shims in there so if the clearances are wrong then you'll know what shims to get. It's much easier to do whilst the head is on the bench than leaning over into the engine bay.
If you don't already have a copy, one thing I would get is Miles Wilkin's book on the Twin Cam engine. It's been revised in the last few years for newer sealants but the main benefit is the number of photos as he takes you through a complete strip/rebuild and the comments along the way about the best way to do things. It's a bit like Brian Buckland's book on the Elan, written with the average DIYer in mind.
Brian
I have a new seal in my stock of parts along with all the top end gaskets (head, timing case, d plugs, valve cover, carb o-rings, secondary throttle (though it's been stripped of the throttles) bases, exhaust, thermostat). Examining the head I have on my bench now, I'm wondering if that plug next to the hole for the head/block breather tube in the existing head is not the source of the leaking. Will be interesting to check when I pull the existing head off.
You make a good point about checking the clearances...will add to the list. Agree it's easier on the bench...really don't want to be fiddling around with it in situ. Spending an hour of bench time checking clearances and figuring out if everything is copacetic is a lot easier than pulling the darn thing apart with the lump mounted in the frame.
I have wilkins' book and have been memorizing it...like I do with most tech manuals. What's that old saying "Trust, but verify"? Trying to line up everything I can (within reason...there is always the 'by the way' things that get you.
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As you are changing the valve seals, you’ll be removing the valves regardless and smear the stems with oil on reassembly.
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The ring locates the cam pulley -- which is why you need to be careful not to over tighten its nut.
I know that to be true since I did it. The result was that unbeknownst to me, the split ring was rotating, or not, I guess, caught on the cam cover, and damaged the groove in the camshaft. I did see little flakes of aluminum in the air and shut it down, but not before the camshaft damage.
It looks to me that the design is such that the ring should be held captive by the sleeve that protrudes from the backside of the pulley. I think mine is ever-so-slightly bell-shaped and doesn't prevent the ring from popping off when the screw is over-tightened.
I accomplished a fix by having a washer welded to the pulley so that I didn't need the split ring any longer.
The initial idea was to change the oil seal to prevent oil from spraying about. I got to do that twice! But I also adjusted valves and re-torqued the head while I was at it.
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When setting the valve clerances the head should be attached to the block. Use an old head gasket and torque the head. If not the clearances will change.
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I'll admit that I've heard that statement before, usually that they tighten up but they really shouldn't change significantly.
The critical dimension is between the valve stem/shim/follower assembly and the cam lobes and I just can't see how that's going to change when the head is bolted down. I agree it's important to torque the cam holders/bearings correctly before measuring and wonder if that's the reason folks have found the clearances altering ? Not correctly tightened on the bench ?
Anyway, we know clearances tighten up in use so all I do is to set them at the high end. Then if they do close up by one or even two thou then you'll still be within spec.
I did see a change last time I did the job on the Europa, most were exactly the same as on the bench but I think one (memory hazy) was a thou different. I put that down to user error with the feeler gauges, it's not logical for a single valve to change when the other 3 stay the same is it ?
Brian
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Just finished cleaning up the head and removing the old bearing shells, and mic'd all the existing shims, so, I'll know what I need to change, if anything. (everything is marked as to which cylinder it came from..and the bearing caps are stamped with a number (as is the gasket flange) and arrow so everything should be ok when it goes back together).
Noted that the set of existing shells were all the same width; according to Ray (and Ken), the #1 and #10 shells should be a bit narrower and the new set coming in has the proper widths. There are no marks on the cam bearing surfaces (or lobes), so, should be good to go there.
Made up a stand so that the head is off the bench top so I won't bend anything when checking the clearances. Wilkins describes doing the clearance check before the head is mounted; I get why you might do it with the head bolted on, a couple folks I've talked to who've done more than one said the difference in a street engine with stock components is nothing to loose sleep over (but also agree that erring on the high side of the tolerance is better than the low side to account for minor bedding in).
Replacing the woodruff key (which was buggered to begin with) and the input shaft was missing the oil galley plug in the back end; pulled one out of my spares stock and put that in.
My plan is to build up this head, with copious amount of assembly lube, and when the lump gets pulled (next month), put the engine up on a stand, and just swap out with the existing head. Also get the clutch done (the output seals on the tranny aren't leaking (yet), and, since the lower link bushings are roached, putting in adjustable lower links.
Debating whether to pull the front cover and rebuild water pump and new cam chain...while it's out...the water pump is not weeping, and have 3/4" of thread showing on the chain adjuster...thinking (along with replacing the transfer tubes) that the hard part (pulling the lump) will be done, so get everything out of the way while it's accessible...
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Hi Bryan,
Personally, if the engine is out, the head off, then I'd do the water pump as well unless you are very, very sure it's only just been done and perfect. The overhaul kits are (were ?) cheaper than the head gasket sets and it's a very simple job to press in the bearing/impellor in a bench vice. The cost of gaskets alone is reason enough to make sure it's 100% before putting the head back on..
One thing that's cropped up on the Elan forums is that pumps fail more often these days because they spend most of the year sitting and not moving every day like they used to do. The anecdotal evidence is around the mechanical seal sticking slightly and wearing more than it should on those infrequent starts. I don't know if that's true or not but I suspect there may be some merit to it.
Timing chain, unless it's definitely worn on the sprockets, I'd leave alone. The Europa still has the original chain from 1972, the Elan I replaced in the 80s IIRC simply because it'd been there since 1968, but to me they just don't seem to wear. I wonder if keeping the right adjustment is the reason and a loose, floppy chain will wear quicker ?
Brian
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Hi Bryan,
Personally, if the engine is out, the head off, then I'd do the water pump as well unless you are very, very sure it's only just been done and perfect. The overhaul kits are (were ?) cheaper than the head gasket sets and it's a very simple job to press in the bearing/impellor in a bench vice. The cost of gaskets alone is reason enough to make sure it's 100% before putting the head back on..
I have a new kit (in the bag) that came in the 2 packing cases of both replaced and new parts when I bought the car. I'm of the opinion that if it's accessible (and would be if the engine is out), it would probably be false economy to bypass it. Just another afternoon worth of work (and a couple o-rings and such, especially if the rear plate doesn't come undone)
One thing that's cropped up on the Elan forums is that pumps fail more often these days because they spend most of the year sitting and not moving every day like they used to do. The anecdotal evidence is around the mechanical seal sticking slightly and wearing more than it should on those infrequent starts. I don't know if that's true or not but I suspect there may be some merit to it.
There is something to that. Though, I think over the last few months, she's probably had more miles put on her than in the previous few years; when I was underneath doing the oil pan seals, I took a look up there and didn't see any rust stain or weeping coolant out of the weep hole. But, again, if I'm in the area, right?
Timing chain, unless it's definitely worn on the sprockets, I'd leave alone. The Europa still has the original chain from 1972, the Elan I replaced in the 80s IIRC simply because it'd been there since 1968, but to me they just don't seem to wear. I wonder if keeping the right adjustment is the reason and a loose, floppy chain will wear quicker ?
Brian
Well, when I had the cover off last spring, it had the proper tension (as measured between the two sprockets) and didn't look like the sprockets were excessively worn; I don't have any chain noise or whining...so, it may be just a case of backing off the tensioner when I go to pull the head (to give me some slack to remove the sprockets) and putting it back together properly.
FWIW, I did take my straightedge and front to rear, side to side, and diagonally on the head I have on the bench right now, and it appears to have been at least dressed flat. Couldn't get my thinnest feeler in there, and shining a light through from the backside of the straightedge, didn't see any light through the machined surface. Thinking, all things being equal, if the block is the same, a fresh gasket and front case seal, new D plugs, new input cam seal, and new valve cover gasket will work properly. At least, that's my hope.
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Also assuming, looking at the exploded diagram, that when I pull the head off, the chain tensioner (red arrow/box, including the sprocket) comes out at the same time with it (or do I release it first and pull out the top, then insert after the head is back on)? Which means I have to back off the threaded adjusting assembly (green arrow/box) down in the block. I understand, from Wilkins, there are special washers involved...another thing to put on a future list, right?
Also thinking out loud that the dizzy has to come out since when I release the cam sprockets and the chain is limp, it will probably drop off the jackshaft sprocket, loosing the timing relationship between the cams and the distributor setting. Not an issue, I'm thinking, since if I line up the crank to TDC as specified to the front cover and the marks on the cam sprockets (or the #4 lobes rocking to the center as in Wilkins, I can reset the dizzy to #1 and get it back to where it belongs (probably easier when the lump is out of the car than reaching over the rear and under the intake...). Am I on the right track?
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Hi Bryan,
Easy answer first - yes, I tend to set the engine to TDC but as you say, once the chain moves independently of the cams/crank you have no assurance that the jackshaft/distributor has stayed put. So the re-assembly means starting from scratch to set the timing. You'll be doing that with the cams anyway and arguably the cam timing is more important than the ignition; duff ignition won't go, duff cam timing could be expensive !
For the next one, I can only tell you what I do, whether that's right or the easiest way I don't know, it's just what I'm comfortable with.
I'll cable tie the cam sprockets to the chain in a couple of places. Slacken off the adjuster bolt/screw and then remove the cam sprockets from the cams. With a bit of fiddling, they'll slip out of the way. This means you don't have to split the chain or remove the cams. If you decide to do the water pump/front cover as well that's optional but it would retain the relative timing of the cams to each other if not the crank, you won't (potentially) be a tooth out on relative cam timing. If you're retaining the chain I'd also retain the sprockets it's been running with.
Mark up a diagram with the bolts to remove. Head bolts are easy, it's the timing cover ones you overlook and then wonder why it won't come apart !
I'm pretty sure I've left the brass tension arm/sprocket in place. It gets in the way when you want to set the head down afterwards but otherwise no problem.
The awkward part is lifting the head with the wear strip/chain guide that's part of the front cover and goes into the head space. It's at an angle so you can't do a straight vertical lift until you're clear - more jiggling about !
General rambling - thinking aloud.
As you're intending to remove the engine block then I think in that position I'd invest in a timing disc and use that for timing. If nothing else you will know if the marks on the cam sprockets are right or not and it's something Wilkins does in his book IIRC ? (I tried a disc but had the engine in the car and gave up as "too hard", going with the sprocket marks instead)
Do you have a sump gasket set to replace as well ? In theory removing the front cover should be possible without the sump but I've never managed it. With the engine out I'd consider replacing every potential leaky gasket/oil seal as a good investment.
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All good points, though it makes me wonder how to slide the head on (maybe I'm getting ahead of myself) if the slipper on the left side is proud of the block but the block has 2 studs as locators....maybe I'm just overthinking...the TC is a new experience (tearing apart 821s and doing jug seals is easy compared to this...;)), so just running through the potential issues.
wire tie the sprockets to the chain are something we do when working on the AJ27 4 litre engines in the early aught Jag XJ series when we do the tensioners (the originals were plastic...and crack...and the chain jumps a tooth...any more than one, and you bend valves in the interference engine design). Great thought!
OTOH, some parts came in to day: new long studs (a couple of them are bent) for the cam cover, zddp paste to put it together, NEW proper size bearing shells, woodruff key, and oil galley plug for the intake camshaft (it is missing). Back to the shop to pull the old long studs out and put the new ones in...
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I left the front alignment stud out then swung the head into position while holding away from the block, then screwed the front alignment stud in and lowered the head. Great fun all by yourself, I would recommend help!
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I left the front alignment stud out then swung the head into position while holding away from the block, then screwed the front alignment stud in and lowered the head. Great fun all by yourself, I would recommend help!
There are a couple guys at the non-profit I am on the board of directors for who are 1) gear (petrol) heads, and 2) offered to help...so, thinking this would be a good test to see if they are willing to step up (and there is an adult beverage refrigerator in the garage, so...) when it gets to that. I can tell you that when I've driven the buggy down to the building we're restoring...there is a lot of parking lot banter and popping engine room lids...
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Getting things lined up to set my valve clearances. There is a range in the book, thinking that setting the clearances at the wider end of the spec is preferable to account for bedding in of the valves. I don't think (and am ok with being proven wrong) that any wear on the lobes, bucket, and shim is minimal and most of the wear will occur at the valve head due to the pounding on the seat as it closes rather than what should be constant contact of the bucket, shim, and top of the valve stem.
Thoughts?
(photo of emptied out head ready for new bearings, graphogen, and cams for reference.)
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An interesting issue I found is that you will get slightly different intake clearances with the alternator belt installed and tightened. I think this difference will go away when the the cam is rotating on a bed of oil on the bearings.
However, it is puzzling when you first encounter it.
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That is very interesting.
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I would think spring pressure normally pushes the cam upwards in the caps leaving the bearing clearance at the bottom, tightening the belt overcomes that tension and pulls the cam downwards leaving the bearing clearance on the cap side :confused:
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Bryan: I vaguely recalled that somebody concluded that the consensus is to set the clearances somewhere other than exactly what the manual says.
I now remember, it was Rob Siegel, and he wrote about it here: https://www.hagerty.com/media/maintenance-and-tech/laborious-process-of-valve-adjustment-in-a-shimmed-engine/ (https://www.hagerty.com/media/maintenance-and-tech/laborious-process-of-valve-adjustment-in-a-shimmed-engine/)
He's not really a Lotus aficionado, but he's a knowledgeable amateur mechanic (much more than I) and he asks questions. Maybe he even asked about this topic here. And he lives not too far from you in the Boston area.
Vince
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Bryan: I vaguely recalled that somebody concluded that the consensus is to set the clearances somewhere other than exactly what the manual says.
I now remember, it was Rob Siegel, and he wrote about it here: https://www.hagerty.com/media/maintenance-and-tech/laborious-process-of-valve-adjustment-in-a-shimmed-engine/ (https://www.hagerty.com/media/maintenance-and-tech/laborious-process-of-valve-adjustment-in-a-shimmed-engine/)
I think that clearance dimension in the article refers to the very early manual for the Elans where the inlets were 5-6 thou, exhausts 6-7 thou. But that was in '63 and the original 105bhp TC engine, not what was used in the Europa TC.
I don't know when they increased the clearances but by the time I got my first Lotus manual in the mid 70s the clearances had become the 5-7, 9-11 that we know today. In fact I only know about the earlier dimensions because I bought one of the original S1 Elan manuals (ex Len Street dealership) which ironically has far better detail than the later one I was/am using !
I've not found clearances altering with belt tension but given the spec on allowable cam bearing clearances I could see how a thou' of so difference could happen. With new bearings I doubt you'll have a problem, especially if you go for the upper end of the ranges.
Brian
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***DELETIA***
I've not found clearances altering with belt tension but given the spec on allowable cam bearing clearances I could see how a thou' of so difference could happen. With new bearings I doubt you'll have a problem, especially if you go for the upper end of the ranges.
Brian
That's what I was thinking, Brian. I did manage to pull off (and keep track of) the buckets and shims last night and wrote down the thicknesses (of those I could see) etched on the shims. I'm going to pull out my micrometer (it was 9PM last night when I was fiddling with it, if I'm honest) and check to make sure what's etched is what it is.
I'm waiting for a shipment of plain 5/16-24 nuts (as well as the 5/16-24 nylocs, and a bunch of other hardware to come in...the pleasures of stocking hardware in a second garage 290 miles from my other residence/hangar) to come in so I can torque down and measure the clearances that were ostensibly done by the rebuilder...and decide what changes/new shims or not?/or just leave be as rebuilt.
In the meantime...no snow or salt on the roads here in SE Massachusetts...supposed to be in the high 50s today...thinking getting the oil circulating and coolant up to temperature might not be the worst thing to happen on the last Friday of the year! And, a week from tomorrow will be one year since I was introduced to 3291R: not running, split upholstery, no carpets, distributor out, leaking oil from the pan, and sitting in the air on a 4-post jack in Beverly MA. She's not perfect, not even close, but she is on the road again, and has been, since april of this year.
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Brian- Thanks for the clarification!
-Vince
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Well...assembled the intake side (copious amounts of Graphogen on all the rotating surfaces...per Wilkins). Guess I need to get a set of shims; they are close, but not close enough for me. Caps torqued to specified 9 ft/lbs, no binding when turning the intake cam.
Cylinder Clearance existing shim thickness change to give .007 (ie if existing is .085, then replace with .084 to increase)
1 .006 - .001
2 .005 - .002
3 .008 +.001
4 .008 +.001
Now to mic (going to be a messy job cleaning off the buckets so I can extract them...again, used copious amounts of Graphogen...lol) the existing shims, and give ray a call. They are cheap enough, right? Also need the special washers for the tensioner bolt and pivot pin. Might as well have them in stock.
Was always trained my professional mechanics that getting things as close to their intended tolerances (I could live with #1 and 2 measurements, but if I can get it closer...why not...) pays dividends in the long run. One or two thousandths doesn't seem like a lot, but if you can get it closer without splitting atomic structure distances and the supplies are available...why not if you're in the area?
Still to do, the exhaust side. Do that tomorrow.
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Never go tight. Never ever. A thou loose, maybe. Myself, I always take the time to get it right. Lots of time spent with emory paper, flat glass and bleeding finger tips.
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Never go tight. Never ever. A thou loose, maybe. Myself, I always take the time to get it right. Lots of time spent with emory paper, flat glass and bleeding finger tips.
I'm aiming for the intakes at .007 and the exhaust at .011 so as the seats wear...I've got .002 to allow it to close up thus decreasing the clearance (I don't believe that there is measurable wear on the shim or bottom of the tappet; I'm happy to be disabused of that notion; all the clearance-dependent wear, I think, would be on the valve/seat face; not taking into account guide ovality or wear which shouldn't change the length of the stem.) I'm aiming for loose, as you point out, but within spec. I'm taking my time, and keeping things together in their respective positions.
Three of the 8 shims have no markings as to the thickness; will pull out the digital mic tomorrow and get the thickness readings for the exhaust side after running through the feeler gauge routine. I'll have a good handle on that, and post back the proposed shim solution for comment.
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My question without notice is this:
Presumably new shims come with some predetermined surface finish spec.
Do they wear in more than old shims?
How much are new shims expected to 'shrink' in, say, 10K miles after initial installation? . . imperceptible?
Just curious.
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My question without notice is this:
Presumably new shims come with some predetermined surface finish spec.
Do they wear in more than old shims?
How much are new shims expected to 'shrink' in, say, 10K miles after initial installation? . . imperceptible?
Just curious.
I've had both brand new and s/h shims over the years and can't say I've noticed any reduction in thickness regardless of how old they were. Very often I've noticed a bright area where the valve stem contacts and at first glance this looked like wear, but when I checked with a mike it's just polished. In theory it should have some metal removal if it was polished but I couldn't measure it.
If you take the trouble to get them right using the tolerance for valve seat wear them it's been fit & forget. But I'll admit to being a nerd whenever I do the job. I'll fiddle for so long that you'll only have to show a spanner to the cam bearing studs and they'll start undoing themselves. And when I'm finally ok I'll walk away and come back the next morning to repeat the measurements, just in case the fairies have changed things overnight. ;)
Brian
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Shims and stems wear, absolutely. In the Jag world it is very common to flip them which restores them to their original spec. One to two thou wear is common and I have seen more, a lot more. Make sure you lube the shim, both sides. Oil really doesn’t get in there.
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Shims do not shrink. They do wear.
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As best I can tell, using a micrometer calibrated to 0.000 before each slug measured, and a sliding, yet somewhat firm feel on the feeler gauge...thinner shims increase clearance, thicker shims decrease clearance.
Engine Initial Existing Projected Estimated
Cylinder Clearance Shim Change New Shim Clearance
Intake (.007 clearance)
1 .006 .071 - .001 .070 .007
2 .005 .083 -.002 .081 .007
3 .008 .088 +.001 .089 .007
4 .008 .076 +.001 .077 .007
Exhaust (.011 clearance)
1 .011 .098 --- --- .011
2 .012 .104 +.001 .105 .011
3 .013 .106 +.002 .108 .011
4 .013 .108 +.002 .110 .011
Caps torqued to 9 ft. lbs, existing shims mic'd to nearest thousandths. Graphogen assembly lube, measured on heel of cam with lobe perpendicular to tappet face.
Anyone have thoughts? Want to get this right! Is my logic sound?
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Looks right to me. IIRC, you have marked your followers for their position. It’s probably not an issue on the TC but I might mark the shims with their position and in your notebook note the size of the shim and where it goes for the next time. Check your clearances again after your caps are torqued to mark double dog sure it’s right. I suspect you were going to do those things anyway. :)
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I wondered if the graphogen could be thick enough to affect the measurement? Would it be more accurate (but require an additional disassembly/reassembly) to measure it all dry?
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I wondered if the graphogen could be thick enough to affect the measurement? Would it be more accurate (but require an additional disassembly/reassembly) to measure it all dry?
I'd not want to rotate the lobes dry on the tappets. I'd venture that pushing the feeler in, displaces enough of the assembly lube that it's not a significant issue.
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Looks right to me. IIRC, you have marked your followers for their position. It’s probably not an issue on the TC but I might mark the shims with their position and in your notebook note the size of the shim and where it goes for the next time. Check your clearances again after your caps are torqued to mark double dog sure it’s right. I suspect you were going to do those things anyway. :)
Everything is marked as to its position and bank. Both on the top of the tappet (in sharpie) and inside the tappet itself. Yeah, there are a bunch of notes stapled to the requisite shop manual pages as necessary; after 40+ years of fiddling with these little beasts and absorbing the manual like a sponge when I was the overnight transmission supervisor at ABC Radio, there isn't a lot I've not seen, but managed to avoid the TC formula until earlier this year...which is a new experience, at least on the engine side.
Probably overthinking the whole process and verbalizing it, but, if it clarifies, for future users, what goes into making these things last..why not?
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I was thinking more about any lube on the shims and inside the buckets
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I thought my BDA might be easier to set the valve clearances on because the cams are housed in a cam carrier and taking that off the head takes cams, followers, and sometimes a shim or two. Boy was I wrong! Some shims stick to the followers, some stay in the valve spring retainer and some fall out onto the head or on the floor (and there are 16 of them)! Keeping track of stuff like what size shim goes where is critical! I don't think it's that big a deal with the TC but I think keeping track of what size shim goes where it's a good habit to get in. If nothing else, it will help you order the correct shims the next time.
Lotus Ltd. used to have a shim exchange back in the day but I doubt they still do. There are far more Loti that don't need those shims than do.
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Dunno if this is helpful, but attached is a spreadsheet written by Tim Engel which does the calculations for the shim job. He wrote it with a Lotus 907 type engine in mind, but I expect it could be used for an 8 valve engine, just fine. He even included Sealant Film Thickness (which is probably only relevant to the 907 engine cam trays).
Tim being the thorough gentleman he is, also includes instructions on how to use it.
I trust he's OK with my sharing this as it's posted in the files section of an Esprit group.
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***DELETIA***
I've known Tim for a long time; I modified the file to focus specifically on the TC engine and it jives with my manual calculations. It's vastly simplified (we only have 1 intake and 1 exhaust valve per cylinder...) and I set up the formulas for the loose end of the intake and exhaust; if you speak excel, modifying it for the clearance values you prefer is left as an exercise..
What a way to spend new year's eve, right?
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It's New Years Day (afternoon) here, Bryan . . . 27°C (80.6°F) bright and sunny. 8)
Happy New Year to all and may your shims stick to your buckets.
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It's New Years Day (afternoon) here, Bryan . . . 27°C (80.6°F) bright and sunny. 8)
Happy New Year to all and may your shims stick to your buckets.
Well..being antipodal to us...it's just gone 7:30AM and 37 degrees F out here. Happy new year, everyone.
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New shims in (and RD mic'd and marked them for me, so it saved me a step...but I checked just the same...;)) and the clearances all prove out to .007 for the intakes, and .011 for the exhaust (one exhaust is an RCH tighter than the rest, thinking it's a couple thou; I have some 400 grit carborundum paper...maybe a little cutting oil, and polish it a bit...but that's probably, at this point, being too OCD for even me). Have to pull off the plain nuts and install the nylocs and washers. Pull tappets off, put a little lube on the top of the valve stem, put tappets back in, torque 'em down (freshen up the graphogen since I have to clean off the tops of the tappets to get the valve lapping tool suction cap to stick...)
(Thanks Ray!)
On to putting the cam seal on (I have a supply of them brand new in sealed bags I found in my parts stash, but, I had acquired a fresh one from RD before I knew I had a few bags of them, so, thinking not knowing the age of the ones in my stash, using the fresh on the cam is probably the best path to take.
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Well...done...#4 exhaust is .0105 versus .011...oh well, .0005 tighter is well within tolerance, no? Worked out pretty good. Splitting hairs at this point, so, I could spend time buffing that shim down an RCH or just live with it. Numbers on the outer flanges are the measured clearances; I rotated the cams a couple times to seat the tappets in the bore before measuring, then made sure the tip of the lobe was perpendicular to the tappet, slid the feeler gauge in...light resistance...and noted the size on the flange. And, yes, the head is sitting on wood blocks to keep the valves happy...
Note: the big torque wrench was on the bench being used to set my wheel bolts...realized that some might get the wrong impression that I was using a 5-100 ft-lb wrench instead of a smaller one...they are not that accurate at the limits, so...actually used the inch-pound wrench (the shorter one; take ft-lbs and multiply by 12 to get the inch-pound setting...which in this case, 9 ft-lbs is 108 inch-pounds) to set the new nylocs.
Lots of graphogen, new nylocs and washers, new bearings, new inlet cam seal at the back (I used the fresh seal I had ordered from Ray; it seemed more flexible than the ones in the bag I had discovered), warmed in hot water, single layer of tape over the snap ring, some grease...slipped right on nicely...in it's groove in the head with a touch of RTV in the channel to seal it up).
On to pulling the tranny, then the lump. Progress, right?
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A half a thou tight isn't terrible. I'd rather it be a half a thou loose - especially on the exhaust but I wouldn't sweat it. I might still "introduce" the shim to some wet/dry since it is now known to be tight but if I couldn't measure that close (and I can't) I'd be happily ignorant!
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A half a thou tight isn't terrible. I'd rather it be a half a thou loose - especially on the exhaust but I wouldn't sweat it. I might still "introduce" the shim to some wet/dry since it is now known to be tight but if I couldn't measure that close (and I can't) I'd be happily ignorant!
At some point...it's really splitting hairs. if it was outside the range entirely (and it's not...it's within spec, this is not a blueprinted engine by any stretch) then it might be cause to pull out the wet/dry and some cutting oil and having at it...and there is noise on the FB page about the clearances changing when the head gets torqued down. I'm not going to worry about it; Wilkins doesn't mention any issues in his book, neither does the factory manual, and except for my OCD following of both manuals while I'm doing this, pretty sure I would have caught that warning. I'm set at the maximum of the limits published; if anything, I'm thinking that even if it does move, it's not going to change enough to worry about; I'll be more concerned with valve seat wear closing it up over time as the valve receeds in.
Pretty sure that Miles (considering the number of engines he built over his career) and other folks I've talked to (Ralph at RS, Ray, Banks, and a fellow lister here (and on FB) who has a lot of experience with the twink) would have mentioned it when I discussed the job and my approach with them. No one mentioned it. Worst that happens is that I pull the VCG, d-plugs, remove the sprockets, tie up the chain, and re-shim. Going to have to pull the VCG anyway to retorque in 500 miles anyway, so I'll spot check then (or if any strange noises emanate from the thing when I start it.)
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I think you misunderstood me. At a half a thou within spec you don’t need to do anything nor is there anything to apologize for (I know you’re not apologizing but I think you get my drift). I was only describing my OCD. If I knew I was only half a thou off, I might be tempted to rub off that half thou regardless how useless it would be.
You’re golden, obviously! I can’t wait to hear your first report that it made noise! :)
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I read that comment on FB as and thought BS. Done some Twinks, lots of Jags and others, and the clearances don't change when you torque down the head. Heck, I've done Aston Martins. You have to remove the head to adjust valves on them!
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***DELETIA***
You’re golden, obviously! I can’t wait to hear your first report that it made noise! :)
Yeah, that will be a good day (assuming, of course...realized that I had not replaced the butterfly shaft seals in the Strombergs when I freshened them up earlier (found the little bag with the seals and brass keepers when I was looking in my parts drawers for something)...that it all goes back properly and tighter in terms of fluid retention. Give me a chance to clean off the block and repaint it (trying to find the right color Ford grey...I think it's the same color they painted tractor engines with...) and generally freshen up/clean the back end...along with a new clutch.
Figure it's a good month of sporadic pulling apart, cleaning up, reassembly, etc. after the Real Work(tm) is done. Pretty sure I have all the bits and pieces on the shelf...if not, it's a couple days for the bits to get here from our PA friend....;)