[avomcd]

How can you tell if you need to evacuate pressures from the motor through the exhaust or with a pump. I run a big-block now with 11:1 comp and no evac system and it runs fine.

 

[avomcd]

suggestion on when to evacuate pressure in engine (help)

suggestion on when to evacuate pressure in engine (help)

 

[Danny Cabral]

I have a feeling the experts will ask you what size engine, how many RPM's, which tension rings, clearances AND if you're inquiring for maintenance (leaks/blowby) OR horsepower reasons. Just trying to help a little.

 

[jpierce55]

I can't say when you should but... My old 460 was roughly 13:1 compression and probably about 480hp. It should have been as much as 650hp but my heads would not support it. I had to run an evac (on the headers not a pump) on it to keep the oil breathers from blowing out of the valve covers going down the track.

I am clueless to when you should run a pump.

It did not run any better with the sysetm that I can remember.

 

[TorinoStyle2]

My old bracket race motor was a 12:1 472 cu.in that I would routinely spin to 7500-7800 RPM's, and it would throw oil all over the place until I installed the header evac system.
When do you need an evac system??...hell, I say always!! even a stock motor could use an evacuated cranckcase.
When do you need a belt driven type??....whenever you can afford one!!

 

[BBBob_M]

How can you tell if you need to evacuate pressures from the motor through the exhaust or with a pump. I run a big-block now with 11:1 comp and no evac system and it runs fine.

Always run some type of evac system. The type depends on the application. One benefit is better ring seal. Crankcase pressure doesn't let the rings seal properly. And a vacuume can add h.p. Amount of vac you want in the crankcase, and the added power you will see depends on if your ring package was designed specifically for said vacuume.