Quote:
Originally Posted by CompClassics
An old drag racers trick is to apply a slight vacuum to the crankcase by installing EGR valves, one way check valves, into the collector area of the header on each side and attach a hose between them and a fitting on each valve cover or a crankcase breather. The Exhaust pulses create a suction which in turn cause a slight vacuum within the crankcase, drag racers looked at it as free horsepower as the pistons were having to pressurize the crankcase when heading to BDC.
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At any moment in time, any pistons heading towards BDC (4 in a V8) are cancelled by the same number of pistons towards TDC.
Blowby gases, combustion chamber pressure lost past the piston rings, is the cause of crankcase pressure.
Applying a low pressure to evacuate the crankcase, and if possible creating a negative pressure within the crankcase helps the rings seal better, since ring flutter will be minimised.
Hence the dragracer power increase.
Many guys run vacuum pumps these days, with a regulated vacuum, about 5 in Hg.
For my cars, I run a PCV plumbed to a hidden log where each runner gets a shared source from.
The fresh air side inlet which becomes the breather outlet under load goes to a Moroso air
oil separator (self drains to the valve cover via 6an) 12an hose breather hose, then comes back to my airbox.
Not a skerrick of
oil in the airbox/hose entry.
Gary