Houston we have a problem

I have all my shims marked. Should I go 1 or 2 sizes smaller to be safe?

Use the table in the manual to determine which shim sizes to use. It makes it very easy to decide and removes any guesswork. Ed

It's a guess if don't know the old gap.

I think if there is a tight gap less than the thinnest feeler on a running engine, assume the clearance is zero. It's probably between zero and .001" if it runs OK but you can't get a feeler gauge under it.

Beaner242 wrote: Bought new valve cover gasket and am checking the valves while I have it off. first one was right on at .05mm according to manual. the rest are all tight, as in cant get a .04mm gauge in there and that is the smallest gauge I have.

There are gauge sets available that go down to .001" (.025 mm). I got one just for this purpose.

loudhvx wrote: It's a guess if don't know the old gap.

You are absolutely right! That's why all gaps should be measured and recorded before pulling any shims. Ed

Where minimal clearance exits --
With cam pointed away from the bucket and thinnest gauge won't insert between cam base and shim, but can turn shim with your fingers, the next size thinner shim will likely provide clearance within specs (being the minimal existing clearance plus .05mm additional clearance that's provided by the next size thinner shim).

Zero clearance exists --
If the cam base is contacting the shim, and can't turn shim with your fingers, a shim two sizes smaller will likely provide clearance within specs. Because an only one size smaller shim will still provide less than .05mm.

Good Fortune!

For the record, all the valve clearance measuring and adjusting should be done when the engine is stone cold (as in after parked overnight).

Good Fortune!