Power Booster/Oil Canister Interference

[theastronaut]

Another option is to use a smaller bore master cylinder without the booster, and leave the brake pedal pushrod in the original manual brake hole for more leverage on the master cylinder. I have a front disc brake swap on my '66 with the original 6.25 to 1 pedal ratio and a 1" bore master cylinder with no booster and the brakes work great without excessive pedal effort. You could use a 15/16 or 7/8" master cylinder instead for even less pedal effort, but you don't want to make it too easy since you don't have ABS.

I don't really understand the point of adding a brake booster when half of the modifications that go along with adding a booster take away line pressure- altering the pedal ration from the stock 6.25:1 to around 4:1, and using a larger 1.125" master cylinder both take away line pressure that the booster is adding. It's better to just use a properly sized master cylinder and the original manual pedal ratio without a booster. It cleans up the look under the hood and the brakes are easier to modulate.