Intermittent crankcase pressure issues

moper said
You're right. And they seal the same way at 0 rpm, 4 rpm, or 7500 if it's working the way it's supposed to. I'm not sold on anything. I'm simply following what your results are telling me based on how an engine actually works. I think that last part is what's being struggled with here.

Higher rpm can push the top ring off the ring land and lose seal. That's what I'm thinking is the issue. But that's a ring, ring gap, or piston problem. Not a head problem...lol. Check the gap on the top vs 2nd rings. If the top was gapped to be large because of the KB directions, and the 2nd was left at the usual ".004 per inch of bore" deal that's your problem. File the 2nd ring gap to .003" more than the top ring gap and clean the bores and it should be fine.
But I've been wrong before and I'm sure you'll figure it out.

Yeah pulling the pistons out is the next stop for sure. I don't wanna take out the bottom end if I don't have to though. Sucks waiting but I can't say I could use a break at this point. Dealing with headers and the starter is never fun. The bellhousing bolts put up the toughest fight though surprisingly.

teringer said
did you get thin race rings? instead of std ring thickness? for the KB pistons? also is the exhaust cross over in the intake blocked or gasket blew out on intake cross over letting exhaust into engine ,I replaced a 200,000 mile engine that I though was wore out turned out just the intake gasket blew out and let exhaust pressure in engine

The intake gasket looked new and was still whole.

Keith Black KB Performance Piston Ring Sets 3910BD8-030

These are the piston rings I used. They came pre-gapped to their suggest standard and we double checked each one as they went into the engine. Not planning on running boost or NOS so I didn't need to file them down.