440 piston ring grooves?

[polkat]

While checking ring clearance in my stock non-HP 440 pistons, I noticed that the second compression grooves are a tad smaller then the tops on ALL of the pistons. I've measured the top ring clearance and got the proper .004" on all of them, so, while I know the top groove wears the most, these are good. But the second rings are tighter. Measuring the grooves, the tops are .082" while all the seconds are .080" on all. Otherwise, the pistons are in nice shape.

I thought all the compression rings were the same size, so what am I missing here? Thanks!

 

[sst3193]

Can't say from direct experience what size those grooves should be, but it makes sense to have more clearence on the top ring, 'cause they have to take more heat. I would imagine that the second ring, being shielded by the first, runs at a much reduced temperature.

 

[Meep-Meep]

Yeah, sounds like a slightly worn 5/64" ring grove to me. It's possible the extra .002" was caused by wear since its at the top and sees more abuse. I assume you are checking this with new rings?