Lotus Elan

Thinner Valve Tappets

PostPost by: paw140 » Wed Jun 02, 2021 12:48 pm

I'm still pretty new to the Elan world and thought I was really close to getting my 69 S4 on the road... I bought it last fall from a guy who bought it in the mid 70's, broke the timing chain in 1980, and it sat ever since. When I bought it, most of the car was in pieces but the engine was mostly put back together and the head was 'rebuilt' by a local machinist who supposedly specializes in older cars. I've recently gotten it to the point where I was able to drive it around the block a few times but noticed a tapping noise coming from one of the intake valves. So I took off the valve cover to check the clearances, and the #3 intake valve had zero clearance. I think the intake valve wasn't closing all the way, and the tapping noise was actually combustion gasses escaping a tiny bit back into the intake.

Last night, I got the camshaft off and removed the tappet, only to discover that the shim size is around 0.050" and is not thick enough to contact the tappet pad. So the tappet is basically pushing on the valve spring retainer, not the shim. I removed the rest of the intake tappets, and the shims range from 0.030" up to 0.050". From what I read on this forum, going thinner than 0.060" is big risk, both for possibly breaking the shim and also to ensure the tappet isn't hitting the valve retainer. Obviously the machinist who rebuilt the head didn't understand the implications of shimming a twin cam, and I won't be using him anymore.

I read in other places on this forum that people sell tappets with a thinner pad that will allow me to use a properly thick shim. I called RD Enterprises and they said that thinner tappets are not available and that I could possibly replace the valve and hope there is enough material to give me more clearance, or worst case that I would need to have all the valves and seats replaced. Is this truly what I need to do, or are thinner tappets available? I measured mine (not super accurate with calipers) and calculate the tappet pad thickness to be around 0.22", which appears to be standard.

Thanks!

Paul
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PostPost by: lotusfan » Wed Jun 02, 2021 1:30 pm

Hi Paul

QED in UK do a thinner cam follower which is 0.16 in thick compared with your 0.22 in standard. I can't help thinking though that you should bite the bullet and have new valve seats fitted to the head.

Link to QED https://qedmotorsport.co.uk/product/cam ... -thin-pad/
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PostPost by: TrevorJones » Wed Jun 02, 2021 2:07 pm

hi Paw120







Hi
I cannot see how a thinner tappet is going to fix the issue, currently there is no clearance gap cam to tappet and the tappet is pushing on the valve spring retainer! You need clearance from the tappet to the retainer (ideally 0.100", you need tappet clearance of 0.006" just to start with.

Rohan posted an invaluable xls spreadsheet on this site some time ago. I would start there and work through the measurements before spending any more time or money on the head. There are a load more settings/clearances to consider in addition to the tappet clearance.The spreadsheet will allow you to work out exactly what is right or wrong and what you can do about it. Getting this wrong could lead to a valve being released from its retainer, valve bounce (incorrect fitted spring length), burnt valves or worst case jamming the valve train up and snapping another timing chain.

Once sorted I believe QED can supply the right valves, springs, retainers, buckets, shims etc (no affiliation).

Hope this helps
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PostPost by: bitsobrits » Wed Jun 02, 2021 2:15 pm

Going to thinner tappets is what my English grandfather used to call bodge stacking. The real issue is that some sort of (unknown) bodgery, likely overly machined valve seats and/or valve heads has already occurred, and the right course of action is to have a credible someone with Twin Cam experience sort the head for you. If the prior shop thought overly thin shims were okay are you going to trust they got the valve guides right, etc?.

Sorting a Twin Cam head isn't cheap, but once done they are good for a very long time given how few miles they tend to get driven these days.
Steve

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Elan S3 1967 FHC pre airflow

Formerly:
Elan S1 1964
Elan S3 1966 FHC pre airflow
Elan S3 1967 FHC airflow
Elan S4 1969 FHC
Europa S2 1970
Esprit S2 1979
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PostPost by: Billmack » Wed Jun 02, 2021 2:20 pm

You would have to thin the tappet from the top. The protrusion inside the tappet would have to be left alone if not increased to make that work. Doesn't bode well for the machinist who did the seats last
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PostPost by: paw140 » Wed Jun 02, 2021 2:33 pm

Assuming that the rest of the valve job was done properly (and this is a BIG if!), wouldn't using the thinner tappets from QED solve the problem? Does anyone know how the thinner tappets from QED are designed? If the thickness is reduced on top side, wouldn't this work? I'd really like to avoid pulling the head and getting all new valves and seats installed, although I realize it may come down to that. I'm a little worried about finding a skilled machinist that can do it right, after my previous experience.
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PostPost by: paw140 » Wed Jun 02, 2021 4:03 pm

I called JAE and they had nothing that could help, but suggested that I call Ken at Dave Bean. Ken was super helpful and suggested that I try thinner tappets that they supply. He said they are 0.090" thinner than stock, so this should give me plenty of extra clearance to install the proper shims. Fingers crossed that I'm not missing something....
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PostPost by: lotusfan » Thu Jun 03, 2021 10:33 am

Hi paw140

I happen to have one of QED's thin tappets and I have measured it up as best as I can.

The outside diameter is 1.3745 in, the inside diameter is 1.325 in. The overall length is 0.785 in. The cam contact area is obviously flat. Inside the top there is a centrally positioned 'pip' which is approx 0.4 in diameter and is 0.16 in thick measured from the cam contact face. The thickness of the rest of the top is around 0.08 in with radiused corners.

Hope that helps but the concensus of opinion is to have new valve seats fitted to your head.
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PostPost by: rgh0 » Fri Jun 04, 2021 4:44 am

You could certainly fit thinner buckets to get an acceptable valve shim thickness and keep the follower from hitting the spring retainer.

However I would be concerned if damage has been done to the collets and retainer from the follower pushing on them rather than the valve tip and I would personally remove the head to inspect. You could do a quick check to look if any variation in depth from top of retainer to top of the valve stem and whether this dimension is different from standard, as significant variation from the standard could indicate damage to the retainer or collets or valve stem.

I would also be concerned why the valve stems are so close to the cam base circle in the first place. The most likely cause is valve seats cut to deep which you could live with by installing the thinner followers but given the work was clearly done by people who did not properly understand the valve train setup on a twin cam anything could have been done wrong and other changes from standard design could be more catastrophic such as using the wrong length valves or incorrect alternative springs or retainers from standard.

cheers
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PostPost by: mr.vman » Fri Jun 04, 2021 9:29 pm

I have successfully used thinner valve lifters in the past. But, There are many situations, variables that might have happened through time. Base circle of cam is larger than OEM. The valve seats could have worn (sunk/recession). The valves faces could also be worn (check margin). I have seen machine shops grind valve tips down for adjustment, to attempt to use the old shims after a valve job. Consider taking the head apart. Cams out, remove valves and check the valves and seats for wear. Measure base circle of cams. Might as well check valve guides also. This procedure should not be that expensive. Most vehicles on the road now have aluminum heads, overhead cams. Machine shops are used to this type of cylinder head. Be safe on this one. Avoid expensive problems later. For the cost of new lifters, you might be well on the way to a good valve job. Hope this helps and does not confuse. Steve V.
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PostPost by: paw140 » Fri Jun 04, 2021 9:37 pm

Thanks for the advice, everyone! I just got my shipment of new tappets from Dave Bean, but I took a quick look at the top of the ‘problem’ valve per Rohan’s suggestion and it visually looks like the part of the valve above the collets is slightly shorter than the rest... meaning the collets might be ready to let go. I’m going to play it safe, pull the head, and inspect everything. Probably better in the long run and these heads aren’t exactly cheap and widely available. I’ll update this thread as I learn more.

Thanks,

Paul
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PostPost by: nmauduit » Sat Jun 05, 2021 8:57 am

paw140 wrote:Thanks for the advice, everyone! I just got my shipment of new tappets from Dave Bean, but I took a quick look at the top of the ‘problem’ valve per Rohan’s suggestion and it visually looks like the part of the valve above the collets is slightly shorter than the rest... meaning the collets might be ready to let go. I’m going to play it safe, pull the head, and inspect everything. Probably better in the long run and these heads aren’t exactly cheap and widely available. I’ll update this thread as I learn more.

Thanks,

Paul


Don't want to mud your decision to pull the head (depending on servicing history etc), but you should be able to swap the collets and inspect the valve tip grove without pulling the head, in case your eager to get back on the road ...
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PostPost by: paw140 » Sat Jun 05, 2021 12:38 pm

I’ve done some research on removing the valve retainer and collets with the head installed and I understand the general procedure, but I don’t quite understand the tool I’m supposed to use. Do I need to make my own? Does anyone have a picture?
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PostPost by: RichardHawkins » Sat Jun 05, 2021 7:03 pm

Paw 140,

I have not done this myself, but Keith Franck (vintage technology garage) in San Francisco sells a tool to do this work. He may be able to help.

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PostPost by: nmauduit » Sun Jun 06, 2021 4:11 pm

I don't have at hand the tool I last used, but it would be something like that :

5495_Right.jpg and
in situ valve removal tool


the idea is that you have a leverage tied to a nearby valve cap stud to press the cup and remove the cotter.

My preferred option to maintain the valve is to pressurise the chamber, some people stuff a rope via a port (or possibly even the spark plug hole) : the tricky part is that one needs to have the corresponding piston precisely at TDC so that the engine does not rotate because of the pressure (I don't usually use the full compressor capability, rather 4 bar max) - it's pretty quick for say changing a broken spring...

good luck !
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