Originally Posted by jayd_2
My '37 Dodge pickup body is mounted on an S10 2WD frame. The brakes are stock Disc/Drum with an aftermarket brake pedal assembly with a 1" bore Corvette style master and a 7" Dual booster, plus check valves F/R and a proportioning valve. The brakes work good but the pedal is a little heavy, I do have a small cam and getting about 15" vacuum at idle.
Would an 8" dual booster help?
I think the 7" dual diaphragm booster should be sufficient, but the larger booster will provide more pressure.
The 15 inches of vacuum is marginal, but in many cases- as long as you have at least
that much- it's sufficient.
But before changing boosters or adding a vacuum pump (the vacuum reservoirs don't really help all that much IMHO), I would consider changing the pedal ratio and/or changing the ignition timing to add some more idle vacuum. This can be done by several methods, depending on whether you have a vacuum advance or not. But the basic idea is to increase the timing at idle, either by adding initial timing by advancing the distributor's position in the block then modifying the mechanical advance mechanism to give the correct total timing, or it might be as easy as changing the vacuum advance from ported to manifold vacuum then resetting the idle speed.
Often raising the idle speed a small amount will give a slight vacuum increase as well- especially in combination w/adding timing.