Crankcase pressure

At WOT vacuum does not make a carburator work, air flow thru the venturis and boosters does. The only way to have vacuum in an intake at WOT is if the carburator flows less cfm that the engine is pulling, for example Nextel Cup cars running a restrictor plate race. These engines are trying to pull more air thru the motor than the restrictor plate will allow. This creates a vacuum below the restrictor plate. Put a vacuum gauge on your manifold and stand on the throttle, it will read 0.


Basically 70440duster has three choices:

#1 - run a header evac system to use with open headers (racing only), then hook up the pcv valve system for street driving.
#2 - an expensive belt driven vacuum system.
#3 - enough breathers installed on the motor to offset the positive pressure.