Horse Power gain guestion

[Duster Don]

I am going to put a crankcase evac set up on my car and I was wondering if any body knows what ( if any?) horse power gain I might expect. My rear wheel horse power is close to 420 hp. A friend of mine read somewhere you could gain 10to 15 HP. That sounds like a lot but I have no idea. How much HP do you loose from the crank to the rear tires?

[B1]

Realisticly, you lose about 20%, but it depends on the type of trans, and so on. crank evacs are like cams, if your engine really needs to get rid of crankcase pressure, then you might gain 20HP. if your engine is not building alot of pressure, then you may gain only 5HP. most racers build the engine with the evac in mind, like going to .043 rings, and using light tension oil rings. then you may gain 30HP by going to the evac.

Brian

[Jims451]

I thought the Evac system mainly is used to help piston ring seal at higher RPMs, and when using the thin "race" type valve springs. I think there is also a side benifit of less air being pushed around in the crankcase "under" the pistons?
Race engine can get a pretty good HP benifet from a crankcase vacuum system, I don't know how much a mild street/strip engine would benifit, or at what RPM level you would see the gain in power?

For example, in the latest CarCraft they ran a 440 engine with and without the windage tray. There was no HP gain below 4,000 RPM, but above that they gained 5 to 7 HP (I think that was the HP gain?)

[Billydelrio]

I think he means thin piston rings, not thin valve springs. I agree that all engines will not respond to a low crankcase pressure the same. Maybe some of our Dyno users can help us with this question.

Don, maybe this year I will get to see you race while I am up in Dover.

Billy

[Jims451]

Yep, your right I ment piston rings.
I must have been half asleep when I wrote that?