My model A has 56 Ford drum brakes in front, 57 Chev drum in the rear. It has a 62 Chev single(1 1/8" bore) firewall mounted master. The pedal ratio is bad and the car barely stops! I want to put an under floor frame mounted dual master, without a booster. I am hoping that by choosing the right bore master along with the proper pedal ratio, that I can get these brakes to stop. (If not I will put disc on front-but really don't want to) What size bore would work best? Any other suggestions?
A smaller bore MC will give higher PSI, but not as much volume. Disc brakes require more volume. Since you have drum brakes you cauld try a 1" or 7/8" MC.
Pretty sure both those applications used a 1" bore master, bigger would require more foot pressure to stop. Also, if you have the room, you should try for at least a 6:1 pedal ratio without a booster.
With the correct pedal ratio [6-1] a 1" bore cylinder would be just right ,7/8 would make for light pedal effort . But you may not like the pedal travel with a 7/8s MC.
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