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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Very true, and way more effective on larger cubic inch engines. Dad and I built an off topic 505 bbc for our drag car and used that exact setup; until we had it dyno'd. The machine shop said, " lets put a evac pump on the crankcase", threw a moroso evac pump on and hp went from 790 to 820hp with no other changes.
Oil pressure was rock solid also, not so much without the evac.