My head's were changed a while ago. The only change I made this last time was oil pump and pan.69chev496 wrote: ↑Wed Jul 15, 2020 10:49 am Let me share my experience. I have a 598 with AFR 335 CNC "S" version heads. I found there was not enough ventilation holes drilled in the heads. What happened is the blow-by escaping the sump into the valve covers to exit the breathers was blocking the oil flow return from the valve covers to the sump and the valve covers were filling with oil during a hard run. This happened under load when the blow by was greater. When the engine returned to idle, the blow by was reduced allowing the oil to return to the sump. I ended up drilling additional holes in the heads to allow ventilation solving my issue. I see the AFR heads were a change you made. Not sure what vintage heads you have. I believe AFR fixed this issue with their newer heads. I can find some pictures if needed.
But my head's are 5-6 years old and this version just came out, actually had to wait for them, they are the V2 if memory is correct. I have seen other manufacturer heads that have the area in the center at top be wide open. Mine are not like that. I can see what you are saying, and that may be happening in my case. There is not much room around the push rods since I am using 7/16 pushrods.