How you plumb the topend of the engine is really dependent on the scavenge ability of the pump and whether it can maintain vacuum on the crankcase when the engine is wound up. If you can't maintain vacuum when the engine is at max rpm you have to vent the crankcase pressure to somewhere or you're going to have blow-by issues.
I started out with a 3 stage Dailey that made vacuum at idle but with the 4.125 stroke crank I have it couldn't maintain vacuum when we revved it up. I added 2 more scavenge stages, I can now maintain 15" of vacuum at 8,000 rpm and picked up 20 hp. I initially ran it sealed but with street driving I started seeing moisture accumulation in the tank oil cap and the valve covers. I plumbed a -4 line from the drivers side valve cover to the top of the tank to turn the air over and cured the moisture issue.
What I have done with the 3 stage pumps is to run one -12 line from the valve cover to the top of the tank, you can run it to the tank breather but you'll just fill with oil quicker.
Last edited by 71RS/SS396; 01-14-2019 at 08:58 AM.
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