Crankcase Ventilation

   Everyone knows an engine needs to breath. That’s the theory of how the engine works as a big air pump. A few even realize that for every cubic inch of air above the piston, there’s an equal amount below it also. The factory uses a simple device called a PCV valve, Positive Crankcase Ventilation. It sucks the air from the crankcase along with all the oil and water vapors back into the cylinders to be re-burnt. It has a benefit of increasing ring sealing and reduces gasket oil leaks. From a racers point of view this isn’t a good option since this stuff doesn’t burn to produce power. It also provides very little vacuum during wide open throttle at the end of the track where racers need it the most.
  Racers have found ways around this problem. For years the old standard was to run hoses down to the header collectors with one way check valves. This used the exhaust pulses to pull contaminates out of the crankcase. This method does work but not as good as it should and it depends a lot on how the fittings are positioned in the collectors. Using mufflers makes the situation even worse.
  Somewhere along the line someone found that running an AIR (smog) pump from a new car would suck vacuum. With the pump, the faster the engine would spin, the more vacuum it produces however the AIR pumps had some downfalls. They were not designed for the rpm of a race engine and they would usually seize up.
   Companies such as Moroso have designed a proper vacuum pump for racers but they can be very expensive. There is a cheaper alternative for the home brew type of racer. You can use an electric vacuum pump found on GM cars.
   The pump came from several models of GM cars made from 1982 to 1992. The vacuum pump was used as an auxiliary brake booster vacuum source. These 4 cylinder cars had problems providing enough vacuum for the brake booster while at an idle. GM solved this problem by using an electric pump.
   It is a good idea to test the pump at the wrecking yard to be sure they pump and then check them at home to make sure they hold the vacuum and operate at the correct pressure. You can find these pumps on the following cars in wrecking yards:

    You'll find these pumps in front of the driver's side front fender well. Look for the vacuum lines running along the fender from the brake booster. Get the electrical plug that goes to the pump and the rubber mounting plate.
    The pump is also available new from GM. Various GM part numbers for vacuum pumps are 22062562, 22034995, 24505066, 10090521. Ford part numbers E4FZ-2A451-A
   Power connections are easy. Black is ground. Red wire goes to a hot source. Black with white stripe goes to switched power. Either the accessory side of the ignition switch or to a manual switch so that the pump can be run during cool down in the pits. The pump is powered via the A connection, but will only run if it receives power from the ignition switch on the B connection.

     Connection A (Red wire) battery positive, 12 volts+ through a fuse.
     Connection B (Black with white stripe) ignition positive, 12 volts+
     Connection C (plugged) not used (not used in factory system either)
     Connection D (Black wire) ground, 12 volts-

   The pump should pull 16 inches of vacuum when run with 13.7 volts and 19 inches when run with 16 volts. You don’t want to pull more than 14-15 inches of vacuum or you’ll start to suck the oil from the piston rings and valve guides and that can have dramatic consequences. You'll get more vacuum out of a crank driven one but a BBC was on a dyno and picked up 40lbs. of torque and 28hp at 7000rpm with the electric pump.
   Racers who need a vacuum pump more than others are the ones who run alcohol. Being able to suck the moisture out of the crankcase will decrease the amount of oil changes needing to be made especially during humid weather.
   One downside to running your crankcase in a vacuum is lowered oil pressure. Because of the lower pressure in the crankcase, the oil is being pulled from the bearings. Although it looks bad it really isn’t. The pressure is low, however the oil volume is still there providing enough oil for the engine to operate.
   Theoretically everyone who uses a vacuum pump whether it’s electric or belt driven should see an improvement of 2-5 percent increase in HP. The system does work. ProStock cars use electric pumps. NHRA realizes the added HP potential and ruled that Stock Eliminator can’t use anything other than a PCV valve and SuperStock is only allowed to use the exhaust evac system.