What size booster did you use with tall valve covers? Single or dual diaphragm? 1.00 or 1.125 bore?

I want to change it now while I have the front clip and motor out. 72 Cutlass Post w/ 455

Thanks in advance

 

Do the math. A stock booster is 11". Assuming engine vacuum is the same in all cases (which may not be the case for a modified engine that needs tall valve covers), the amount of assist you get from a booster is a direct function of the booster area. A smaller single diaphragm booster will have less assist. A 9" booster has 67% of the area (and thus 67% of the assist) of an 11" booster. A 7" booster is 41% of the 11". Obviously a smaller dual diaphragm booster is twice these numbers - 133% for the dual 9" and 81% for the dual 7". If you must have power brakes, consider a hydroboost.

As for the M/C diameter, smaller requires less pedal force but more pedal travel for the same force at the wheels. Conversely, larger requires more pedal force but less travel. I'll note that my stock 70 W-30 with manual disc brakes stops fine without excessive pedal force.

 

Thanks Joe

 

Consider hydroboost, I converted mine for less than $200.