TheSamba.com :: View topic

Thu Jul 10, 2025 5:25 pm

Ok, so AA 90.5 cylinders and pistons. Bently says .003" to .004" piston ring to land clearance. On my AA pistons I have .002" 1st ring, less than .002" 2nd ring. Exactly the same all pistons. I have to say "less than" because I have no way to measure less than .002" as a feeler gauge.

I called AA and enquired, they said their spec is .001" to .002"

That seems tight! Although, all rings can be spun in the groove easily even if dry. And they all fit well for depth, also.

AA says run them...yet I'm paranoid...

Thu Jul 10, 2025 6:19 pm

mcjweller wrote: Ok, so AA 90.5 cylinders and pistons. Bently says .003" to .004" piston ring to land clearance. On my AA pistons I have .002" 1st ring, less than .002" 2nd ring. Exactly the same all pistons. I have to say "less than" because I have no way to measure less than .002" as a feeler gauge.

I called AA and enquired, they said their spec is .001" to .002"

That seems tight! Although, all rings can be spun in the groove easily even if dry. And they all fit well for depth, also.

AA says run them...yet I'm paranoid...

The Bentley manual is referring to the original cast aluminum pistons that would have came in the car. The AA pistons are cast hypereutectic & they wont expand as much as standard aluminum ones will so the gap doesn't need to be as big.

I'm not the expert & I'm sure someone will come along & Tell me how wrong I am.

Thu Jul 10, 2025 8:24 pm

Your good to go

Thu Jul 10, 2025 8:25 pm

.001-.002 is good
.004" is the wear limit IMO

Fri Jul 11, 2025 9:07 am

Do make sure to check them for piston-to-cylinder clearance, then check your ring gaps afterward!

My AA piston to wall clearances were really tight as boxed and needed to be honed.

Fri Jul 11, 2025 2:44 pm

Thanks everyone, for the sanity check! Looks like I am good to go on all counts.

Thanks,

Matt