Master Cylinder Pedal Effort

[kw502bbc]

I need to pick everyone's brain on my brake system for my '57 3100 truck. I have a complete brake system from a '79 WS-6 Trans Am 4 wheel disc setup, including the rear end, which was the right length, and the stock proportioning valve. I wanted to keep the frame mounted master cylinder, and since I built it 21 years ago, the small boosters were almost non existent. I mounted the stock 1 1/8" piston master cylinder on a fabricated frame mount, minus the booster, and it has been trouble free since then, but a rear caliper leak popped up last year. My winter project has been rebuilding the caliper, and was thinking about changing the master cylinder to a 1" unit from a manual drum brake Camaro or Firebird, since it would be a direct replacement, with no tubing changes. My reason for thinking about this change is that it seems the smaller piston would take less pedal effort, but possibly a longer stroke. Anyone ever try this, and would check valves be needed going from a disc to drum master cylinder, or would the proportioning valve take care of the residual pressure? Thanks!:?

[chevynut]

The smaller MC would definitely give you more pressure with a given pedal force. If your prop valve worked before, I don't know why it wouldn't work with the MC change.

[Maddog]

Your assessment is correct. However are you certain you have a 1 1/.8" master now? Without a booster? If so, that should be very, very difficult to press the pedal as in "rock hard".

[kw502bbc]

Yeah, I have to stand on it. Kinda like a "poor man's ABS", cause you ain't going to lock it! It stops well, not as easy as when I was younger!

[Maddog]

Yeah, I have to stand on it. Kinda like a "poor man's ABS", cause you ain't going to lock it! It stops well, not as easy as when I was younger!

YOU NEED TO INSTALL A 1" BORE ASAP

[kw502bbc]

YOU NEED TO INSTALL A 1" BORE ASAP

I plan to change it out before spring. I should have done it long ago, but got used to the hard pedal, and never really had problems stopping. I thought about putting a small booster on the 1 1/8 MC, but it would take a lot of re-plumbing, and I used 304 stainless tubing originally. I found some new aftermarket (Raybestos) 1 inch MCs that look like a direct replacement, and thought if it would work, that would take care of the hard pedal with no reworking of the tubing and prop. valve. Thanks for the advice!