Clearance issues on tappets

Ok, so I’m having some issues with getting the clearances right on my tappets. According to the ROM, the adjustment shims start at .085" and go up by .001" increments up to .110".

The clearance with shim is supposed to be .012" to .014". This means the minimum clearance without shims installed should be .097".

Mine are .056"-.069". It’s too big to not have shims but too small to insert any. I’ve turned the crankshaft one full time to make sure that the tappets weren’t just stuck somewhere above the valve, but they aren’t.

Any ideas where I’ve screwed this up?

Was any machine work done on these heads? Reseating valves, etc.?

It might help if you clarify which engine you’re speaking of. 5.3 H.E.?

Right, sorry Kirby. It’s a 1990 H.E. The heads and valves are brand new, all i had to do was lap them in a little to get a good seal.

If the heads and valves are new, did they recut the valve seats? It may be that they’ve taken more off the seats than they should.

Hopefully the heads are still off the car. The best, although most expensive option is to take them back for installation of new seats. Get them to cut the seat height to give you around a 100 thou shim requirement.

If they suggest cutting the valve stems down instead, consider this carefully. Some valves have hardened material at the end to minimise wear. If you cut past this into softer material you may have trouble in the future.

You can get custom shims made to any thickness, but you really don’t want to go much under the minimum stock size.

It sure sounds like a machinist got aggressive with the seats. Ouch.

Well, I’m happy to report that the only issue with the new heads is me being stupid and getting in a hurry. I was cleaning shims to see what all sizes I had at home when I realized that I had forgotten to install any before I checked the clearances! :man_facepalming:

Thanks for the replies and advice, guys, but it looks like I just need to pay more attention to what I’m doing.

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You might also want to check the clearance spec. The Non-HE spec is .012-.014". The HE calls for .010-.012" . I have found that .012" works best inlet and exhaust.

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