What's going on with my valve clearances? (sanity check)

[The Veg]

It may be that your new shims are not seating properly in the spring caps ..... have a read through this thread, particularly Tim Engels post.

viewtopic.php?f=39&t=46183

Noted. I have two types of shims, some the 'disc' type and some the much smaller 'cap' type. Some of the disc types have a chamfer around the edge of one face, one or to have it around both edges, some do not have a chamfer. I'll put this on my list of things to check, but so far they've all fit smoothly.

[The Veg]

Check that the Shim contacts the Valve Stem and NOT the Collet Retainer
Alan

Also check what shim thickness are you using and what is the shim pad step size inside the follower as you can have the top of the retainer contact the bottom of the follower rather than the shim contact the shim pad if the shims are to thin for you retainer and follower combination.

In other words, make sure that each shim stands proud above the top of the retainer? Yes, they do.

[The Veg]

If none of the posts from the previous poster's help I would be inclined to check the fit of the followers in their respective sleeves, and flatness of shims / valve tips / followers (pads underneath included).
I have seen clearance issues on engines with too much follower clearance which allows the follower to tip and give a different figure each time. Also, poorly ground shims (ie not completely flat all the way across) will give problems.

The WSM says .0014 max between the follower and sleeve; my thinnest feeler gauge is .0015 and it would not go into the gap on any of them and they all feel nice and smooth and free of wiggle when I slide them in or out. That said, the wear-pattern on the follower in the picture is typical of what I've seen on all of them. To my novice eye it looks like their motion hasn't been completely free of tipping but I understand that a tiny amount will happen with even the smallest gap. Does it look OK or suspicious? How much difference in diamater should I see between the worn areas near the edges and the unworn central area?

Follower pads: I have checked two of them, measuring four places around the circle of the pad and on one all four were within .0005 of each other; on the other one they were within .001.

As for shim flatness, that's going on my list of things to check next session in the garage.

I also saw this problem on a BDA which just about drove me to never touch one ever again : 16 valves isn't always better when they've all got problems!

I used to have an Esprit. I did the valve-adjustment with it once and didn't have anywhere near this amount of headache with getting the 16 clearances right! That head had about 23K miles on it vs maybe about 1K since my TC head was rebuilt before I owned the car. The rest of the job with that engine, dealing with all the belts in situ...I never want to do that again!

[The Veg]

+1 to what Rohan and Alan said regarding the follower contacting the retainer.

Doesn't seem to be an issue since all shims are tall enough to protrude from the retainers.

Have you gone back to the original shims you removed from the engine (the ones that got you .004” on the intake) to see if they yield the same clearances as before? Trying to obtain repeatable results is usually where I start when chasing ghosts like this.

If I'd known that this situation or question would come up, I would have tracked each one...but alas, when I ran into problems I swapped some around and any not in use got set side with no more ID than their thicknesses (although based on my notes, I may be able to reconstruct that setup). But in the spirit of repeatability, during today's session I spun the shafts a few times then measured clearances again, not having disturbed anything since yesterday's measurements. For today's on each one I measured, spun the cam twice, then measured again and all were the same before and after two spins. Here's what I got:

Yesterday
I E
1 .009 <.0015
2 .012 .012
3 <.0015 <.0015
4 .013 <.0015

Today
I E
1 .009 <.0015
2 .008 .011
3 <.0015 .014
4 .010 <.0015

But before yesterday's attempt at adjustment, I2 measured .010, I3 .018, E1.021, E3 .021, E4.032(!).

According to my notes the initial measurements before the head was off were:
I E
1 .004 .008
2 .004 .011
3 .004 .014
4 .004 .016

[The Veg]

You are hereby granted unlimited access to my shim collection. Should you need it I'll be over your way in the next week.

Wow Mike, that is an impressive collection! I don't know if I'll know what I really need in time for that, but I still have your contact info and can get in touch if need be- thanks in advance!. Do let me know when you'll be by this way in case you have time to drop by and see project in person! I have a biz-trip in your direction in a couple of weeks so I might be able to do likewise.

[The Veg]

Are you re-using any shims that have a slight depression worn in the center where the valve stem previously made contact. If so, then it's imperative that you measure the shim at the center by using a micrometer. It's round anvil will fit down in the depression and measure the actual working thickness of the shim... which is something less than the shim's rim thickness. Then make absolutely certain that you install the shim with the depresion side down against the valve stem.

I hadn't thought of that, but if any do have such depressions they are not dramatic-enough to be visually obvious. By 'round anvil,' do you mean that the anvil should be rounded on the end? Mine has a nice flat anvil, which seems to be pretty close to the diameter of the tips of the valves. For the 'cap' type shims it takes up most of the space inside the underside. For the 'disc' type shims I did always measure the center, but did not think to check whether one side or the other had a depression since none was visually obvious.

In any event, this too is now on the list of things to check next session.

Every used shim has two thicknesses... the rim thickness is greater, and the center depression thickness is less. It is okay to use either thickness, but you must keep your head engaged and match your measurement to how the shim is installed.

Depression up against the tappet = effective.rim thickness.
Depression down against the valve stem = effective center thickness.

Definitely noted!

And Tim, I appreciate your advice as always. I'm the same The Veg that you may remember from the Esprit forum and Turbo Esprit mailing list. I'm still grateful for the guidance with the Esprit's valves, which were much less troublesome at least in the actual clearance-work.

[rgh0]

Hey Veg,

You are hereby granted unlimited access to my shim collection. Should you need it I'll be over your way in the next week.

Cheers,

Mike

Hi Mike - it looks like you have an identical shim collection set like I bought off the internet many years ago at a bargain price when someone was clearing out old stock !!!

cheers
Rohan

[rgh0]

if your confident you shim measurement and shim change maths is consistent and correct and also If your confident the shims are resting on the valve stems and being contacted correctly by the follower pad and there is no interference affecting them and you still get inconsistent clearance measurements and also that the follower is not moving in the guide and tilting and affecting the clearance measurement then you need to start digging deeper into the valve train assembly.

In general I have found that impression of around .001" in a shim from the valve stem is usually visible. As other have said if reusing a shim with a visible impression from the stem put that face with the impression to contact the follower pad as you can get inconsistent measurements if the valve stem is not fitting exactly into the impression.


The next two further areas I would check next are:

1. Cam bearing clearances - excessive clearances can allow the cam to move around in unpredictable ways affecting the measured clearance depending on how it is sitting in the journals versus the clearance being measured.

2. Valves, Valve springs and followers - bent valves, damage or collapsed valve springs or followers sticking near their top of their travel can all result in the valve not returning to the fully closed position consistently and thus the clearance measurements randomly varying. One way to test for this is the measure the clearance and then use a wooden rod and hammer to bounce the valve and follower a little to see if the measured clearance closes up a little

cheers
Rohan

[alan.barker]

You need to be sure the dia of the Collets is not too small(correct Collets) or they will be too deep in the Collet Retainer Tapered hole
Alan

[avro]

You need to be sure the dia of the Collets is not too small(correct Collets) or they will be too deep in the Collet Retainer Tapered hole
Alan

The suggestion by some that the cause of your problem might be that the underside of the cam follower is hitting the top of the valve spring retainer before taking up the tappet clearance and opening the valve is certainly a very strong possibility .
As Alan suggests a pair of collets with a slightly larger diameter will cure the problem.
I do keep these in stock and when fitted the retainer sits .050” further down the valve. If you do fit them then you will need to check that the valve springs do not get close to becoming coil bound at full lift , especially if you have high lift cams fitted.

An alternative fix if you have standard cam followers fitted (.220” pad thickness) is to use a thin pad cam follower.
These are readily available at .160” . This will then allow you to use a thicker shim and thus cure the problem of cam follower to spring retainer contact.

Either way if you discover that this has been the cause of your problem what l would advise is that you change the cotters as a matter of course . The constant hammering effect from being loose and tight on the valve can shear the locating rings on the cotters resulting in a dropped valve.

Nick

[2cams70]

I got rid of these issues hopefully by installing top hat shims!! The disadvantage of course is that they have to be individually machined because they aren't readily available in a wide range of sizes.

[Esprit2]

I hadn't thought of that, but if any do have such depressions they are not dramatic-enough to be visually obvious.

A 0.001" deep depression would not be dramatic to the eye. But when your entire target clearance range is only 0.002" wide, one thousandth is a lot. I was going to say that shimming valve clearances is a matter of splitting hairs, but hairs are really fat compared to what you're playing with.

By 'round anvil,' do you mean that the anvil should be rounded on the end?

No, flat on the end. "Round", not spherical. A typical micrometer is like a C-clamp. On the fixed side, there's a short, cylindrical pad with a flat end. The moving side is also cylindrical with a flat end. In some places, both the stationary and moving sides are referred to as 'anvils'.

And Tim, I appreciate your advice as always. I'm the same The Veg that you may remember from the Esprit forum and Turbo Esprit mailing list. I'm still grateful for the guidance with the Esprit's valves, which were much less troublesome at least in the actual clearance-work.

Yup... the Lotus community is small enough that many of the same names show up in different 'model' forums. It's interesting to see who you know is going to show up somewhere else.

Stay well,
Tim Engel

[Esprit2]

The WSM says .0014 max between the follower and sleeve; my thinnest feeler gauge is .0015 and it would not go into the gap on any of them and they all feel nice and smooth and free of wiggle when I slide them in or out.

The chances of accurately measuring a 0.0015" or less arc'd gap (cylindrical, not flat) with feeler gauges is pretty much nil. You would have better luck accurately measuring the tappet OD with a micrometer, and the bore ID with a bore gauge, then subtracting. For reference, typical household kitchen aluminum foil is about 0.001" thick. But you would be hard pressed to use a narrow strip of it as a feeler gauge. It would be like pushing on a rope.

That said, the wear-pattern on the follower in the picture is typical of what I've seen on all of them. To my novice eye it looks like their motion hasn't been completely free of tipping but I understand that a tiny amount will happen with even the smallest gap. Does it look OK or suspicious? How much difference in diamater should I see between the worn areas near the edges and the unworn central area?

The original Lotus tappets were chilled cast iron. Okay for street-stock, but not really up to the task with aggressive high lift cams and high rpm. In 1988, Lotus switched to steel tappets, and discontinued the cast iron version.
A026E0024Z, 0.218" thick crown, 22mm skirt, Pre-1988, Chilled Cast Iron.
B920E0017Z, 0.224" thick crown, 21mm skirt, 1988 on, Steel.

The iron tappets had a 22mm skirt length, and the newer steel ones were a millimeter shorter, at 21mm. Neither was particularly generous with skirt length, and the tappet could be more inclined to cock in the bore with aggressive high lift cams. When the tappet is prone to cocking in the bore, bands of wear marks and scoring near the top and bottom are typical. Such wear/ roughness is not a good thing, and to my eye, the tappet in your photo should be replaced. Lotus later issued a TSB advising that their steel short skirt tappets should not be used with aggressive high lift cams.

If you shop around with independent Lotus specialists, you'll find that most carry non-Lotus steel tappets that have both longer skirts and a lower price.

The last time I checked with Garry Kemp in the UK, he offered two steel tappet options.
0.220" thick / 23mm skirt = Near stock, but a longer skirt.
0.240" thick / 25mm skirt = Thick Crown for re-ground cams, and long skirts so a tappet that must extend further out of the bore to follow a smaller, reground cam lobe won't run into issues with insufficient bore engagement.

And the last time I checked with JAE
0.240" thick / 23mm skirt,0.220" thick / 23mm skirt,
0.200" thick / 23mm skirt,
0.180" thick / 23mm skirt,
0.140" thick / 23mm skirt,
Steel, Hi-performance/ race upgrade tappets for Twin Cam, also fits the Lotus 9XX engines.

It's been quite a while since I checked with them, and what either company offered seem to be in flux over time. If interested, call and ask what is currently available before making any plans.

Stay safe,
Tim Engel

[The Veg]

By 'round anvil,' do you mean that the anvil should be rounded on the end?

No, flat on the end. "Round", not spherical. A typical micrometer is like a C-clamp. On the fixed side, there's a short, cylindrical pad with a flat end. The moving side is also cylindrical with a flat end. In some places, both the stationary and moving sides are referred to as 'anvils'.

That's what I thought, but wanted to make sure I wasn't missing some knowledge. Thanks. This is a learning experience at every turn for sure.

[The Veg]

Thanks gent's for all the advice. With so many things to check and possibly rectify, much of it being beyond my expertise or shop capabilities, I'm going to pull the head again and have a pro give it a going-through. The good news is there is an expert in my local area, the bad news is he's in the process of moving his shop and won't be ready to take it until late May at a guess. I was going to wait until the engine was done and basic road-testing was satisfactory before putting the interiour back together, but I guess I could focus on doing that and other repairs while I wait for the head.