As said several things enter into this besides bore ,mainly pedal ratio. A 1" bore dual will work just fine with the early Ford brakes. A 1-1/8 will cause a higher pedal effort due to the increase in surface area of the piston compaired to a stock 1-1/16 Ford MC ***uming the same pedal ratio. Will it be enough to be objectionable ?? Maybe. Brake MC sizing is not a place that bigger is better.
True. Going a bit smaller (1/16") can give a 'power' feel, at the expense of slightly more travel. But then, too, real power brakes have more travel...and more sponge. Cosmo
The bore of the master cyl is 1 1/6 or 1.0625 the area of which is .8862 and since you are using a dual master you are cutting the brake system in half therefore you need the area of the two pushers to be half the area each. Half of .8862 is .4431 and the area of a 3/4 or .75 bore is .44156 about as close as you are going to get. The formula is Pi(3.14) x R2(radius x radius) = area of a circle. Bigger is not better! The correct size and proper pedal ratio is all important. Pedal ratio should be 6:1 for manual brakes and 4-5:1 for power brakes.
Not disagreeing, just sayin'...when Ford changed to a dual M/C in 1967, the bore remained the same and the W/Cs remained the same...but you had a dual M/C instead of the fruit jar. Cosmo
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