WEll, i finally got off my butt today, and pluged by vacuum gage into the crank case (the line that comes off the intake tube), and much to my surprise it started climbing rapidly to 7In HG. Wow, that is pretty good. This also stayed constant regardless of RPM, which is an even better thing, i didnt rev to high, but up to 4000 it never moved, never even flickered, so i figured it was good. I dontlike free reving my motor, and my line wasnt long enough to go for a drive and have the guage inside the car. So that just leaves the fact that i dont like the fumes its sucking out going into my fresh caharge of fuel, but if i put a pan evac on, i probably wont get as much vacuum (probably 3 to 5 in). So for those of you interested, there you go. I will test an s as soon as i remember.

Beecher

 

I've been noticing racing motorcycles using a tap on a header tube to vacuum the crankcase, and I have an ATV hooked up like that. My brother-in-law actually has a belt-driven vacuum pump on his '71 Camaro's 540 cubic inch engine. All this avoids crankcase vapor contaminating the intake charge. -Jeffy.

 

The main reason for putting a crankcase in a vacuum is to lessen windage losses. The crank, rods and pistons churning away at over 6000 rpm generate a great deal of windage, which is the result of all that spinning stuff blowing air around inside the crankcase. In extreme cases, this cause the spinning, blowing air to scoop oil out of the pan and throw it around the crankcase. This creates a great deal of increased drag, foams the oil and lessens the amount of oil that can be pumped through the engine by the oil pump. It also interferes with the drainback of oil from the upper head areas back to the pan, trapping oil in the top end of the engine and creating a starving situation. If you can manage to pull a near perfect vacuum in the crankcase, windage will be eliminated. Even a partial vacuum has benefits. The downfalls to putting a vacuum on the crankcase are that is sometimes causes premature oil seal wear (rear main and timing cover seal, cam seals in belt-driven OHC engines, etc) and an increased infiltration of blow-by gasses in the crankcase. Also, in some engine designs, lubrication of certain internal parts might rely on oil being 'blown' around by windage and air pulsations. These engines might see incresed wear in those areas.