Thread: Crankcase Vacuum For Power

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I have plumbed my 454 with a Moroso kit to suck from the valve covers to the header collectors. Then I began to wonder if this setup has the potential to cause problems - like pulling gaskets in! I do not have a PCV setup as that would seem to defeat the purpose. What do I need to do, or lookout for?

Thanks, Rad

What do you have for breathers? The header evac system won't pull enough vacuum to suck a gasket, at least I've never had them do it.... The best part is that at high rpm all the positive crankcase pressure has a place to go besides pushing the valve cover gaskets out.... As long as you installed the backfire valves in the hose at the header, shouldn't be any problems.....

Yes, backfire valves are in the tubes welded into the collectors. However, the vacuum outlets are stuck into the valve covers where the breathers would normally go. So, no breathers at all. No PCV.

I would make sure you have baffles in those valve covers............ Lon

You'll be ok.... Never had a problem with the scavenge system without a PCV valve.... The cylinder scavenging will not pull enough of a vacuum to pull a gasket in....

As rat said, you should have baffles and/or some tall breather tubes in the covers.... Simple system that works good and no added maintenance.....

Yes, there are baffles under the valve cover breather holes. I assume you are concerned about sucking oil out of the rocker arm galleys. But would not breather tubes defeat the purpose of the suction. In that the suction generated off the exhaust would only pull air in from the breathers, and not create a crankcase negative pressure?

Yup, somewhat. That was my concern, that you didn't have a couple extra breathers that would limit (somewhat) the amount of negative pressure in the crankcase.... Running the system as you have it will work fine. Without baffles it would pull some oil. On one of my BBF valve cover sets, I run a tall, baffled tube with the evac hoses and caps connected to them... Never pulls any oil, but sure does a nice job of pulling enough negative pressure to get the oil vapors out of the engine.....

A good working system can and will pull a cork gasket from a Moroso chrome steel valve cover---use a cast alum and a paper gasket or o-ring gasket and you won't have any problems

On my set up that pulled the gaskets it was also drysumped which created higher vacume

Thanks All,

I think I just need to run it and see what happens. I was thinking of some nice sand cast ribbed valve covers anyway...........