In order of success, from least to best, here is what I have tried for crank case ventilation.
Normal PCV system with a breather on one valve cover and the PCV on the other. Works poorly at high RPM due to lack of vacuum. There was oil vapor venting from the breather as well.
No PCV and breathers on both valve covers. Works fairly well but can be messy. Efficiency was cut when the breathers were piped into the air cleaner to keep the valve covers clean. I also had to gut the foam material from the breather caps after piping to the air cleaner.
No PCV and Mr. Gasket header ventilation system. Works the best so far. The engine is sealed except for the two breathers connected through check valves to headers. I use a 3" exhaust system with Flowmaster 40's. There is virtually no back pressure and it has excellent vacuum at both hoses, at least at an idle. The Mopar style breathers do have filters in them that reduce airflow though. I may try my other "gutted" breathers.
Currently I have no oil leakage unless I am under WOT and above 5K rpm. For the most part I had no leakage from any of the ventilation systems I have tried unless I was WOT at 6K.
JohnZ, I agree with your statement. I have put together a lot of small blocks, but this is the first 400, and I have seen crank case pressure but have never seen a leak like this at a distributor. Please keep the ideas coming, I never discount any of them.
I may not be able to read any replies for a few days. At 5:30 AM tomorrow I head for Joliet to the Spring Nats. Anyone else going to be there?