My old shop teacher had a cranked up 460ci ford around the 500hp range and he took and mounted one-way check valves in the exhaust then attached the crankcase vents off the valvecovers down to the one-way valves on the exhaust(if I remember correct). This in sense gave the engine vacuum pressure in the crankcase at higher rpms/exhaust flow, he said it netted about 20hp on the dyno. It works for gassers, but does the same concept work for diesels? That is making a vacuum in the crankcase to gain power?
Tim.

 

Same principle applies. However, guys who have tried to pull a vacuum on the crankcase have sucked in the tappet cover gasket. Most installs I have seen of exhaust evac tubes on CTD's use extra breathers in the rocker covers to prevent this. The purpose of these installs is to use the evac tube to control blowby under high boost to prevent oil leaks due to excess crankcase pressure, not to pull a vacuum.

 

The mentioned set up is to lessen windage in crankcase at high rpm to help keep down oil being pulled into crankshaft and costing hp.
James

 

One thing to note about this... It only works if there is almost no backpressure. DONT try this with a muffler in your exhaust system, or you will be pushing exhaust and soot INTO the engine instead of evacuating it. Pretty much every drag car that runs a wet sump uses this method, and it is very effective. Even better is an actual belt driven vacuum pump, but my class doesnt allow that...


KP

 

I've heard about using a actual pump to create vacuum vs. the exhaust route. You said it cannot be done with a muffler set up, how about a straight through muffler? Seems to me like a worth while venture, but is there a downside to it?
TIm.