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Valve lash - Is this how it is done?

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Ray Brandes

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We are rebuilding a 907 engine for a Jensen-Healey. We are having the valves re-ground.
We are eliminating the paper gaskets under the cam towers and will use the 515 sealant.
Both of these things will reduce the thickness of the shims.
I will make some temporary shims, a bit undersized, and measure the lash.
Based on these measurements I will grind the original shims for the proper lash.
Is this how it is done?
Regards, Ray
 
You make it sound easy. If you have the skills and tooling to make the shims, that will help. Also make a good chart of all your measurements. I've not done a Lotus but in the past did a Fiat and a SOHC Triumph TR7 (Also read that the TR7 shims are the same size as the Lotus). Both took me several tries to get even reasonably satisfactory clearances. The more accurate, orderly and methodical you can be (I'm none of those) the better the results.
You might find this interesting too:
https://www.jensenhealey.com/forums/view_topic.php?id=746&forum_id=2&page=3
Tom
 
Done many, including my own three Lotus'. Shims are available at Dave Bean Engineering (NFI). I've a set made from brass and cut to 0.040" to use as a "base" reading and do the math to come up with proper clearances. A felt-tip marker is useful to write the measurements on the lip of the head adjacent to each pot.


BTW: The shims are hardened, need to be lapped to make 'em thinner. A real chore to be accurate with those little buggers. Best to get the proper thickness from a supplier.
 
Thanks guys! I have a surface grinder to set the shims to the correct thickness. I made a steel set of .085" for a base and went from there.
I kept putting in feeler gauges going up .001" at a time until one wouldn't go. I recorded that value and the one under it that went.
I used these measurements in a spread sheet to get the new shim values.
Regards, Ray
PS: Made urethane tail light gaskets for my BMW 700. Turned out great!
before-after.jpg
 
Ray,
As with your points gap question, I'm too late to the party to be helpful, but...

The shims are case hardened, not hardened all the way through. If you grind them much thinner, the case hardened layer will end up too thin. A couple of thousandths is okay, but if you plan to make up for both deleting the gasket and grinding the valves, I fear the shims will have to be ground too much, and the hard layer will become too thin.

Deleting the cam carrier gasket also involves cutting a counterbore around the front oil passage/ dowel pin, and installing an O-ring there... one per cam carrier. If you know all of that, then you're good. If not, ping me and I can give you the dimensions for the C-bore and O-ring.

Basically, you're on the right track, just watch those details. The clearances close up with wear, so always shim to the top of the clearance range. That will give the longest mileage interval before the job has to be re-done.

0.005" - 0.007" Intake... Target 0.0065" dry.
0.010" - 0.012" Exhaust, Target 0.0115" dry.

The anaerobic sealants have a half-thousandth film thickness. So when the Loctite 515 or 518 is added during final assembly, the film thickness will 'float' the head up another half-thousandth, and give a final 0.007" Intake, and 0.012" Exhaust.

515 & 518 are both good. But 518 is more fluid, easier to spread (paint it on with a flux brush), while simultaneously better at gap filling. Given a choice, I use 518. But if you have 515 it works well... it's just more difficult to apply.

Regards,
Tim Engel
a Lotus fan
 
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