Here's the scenario: just installed a new Wilwood master cylinder on my '56 Buick and the pedal is as solid as a rock and has no travel. All of the brake line, flex hoses, wheel cylinders, and shoes are only six months old. The brakes are properly adjusted at each wheel. I've bench bled the master cylinder, and have bled it half a dozen other times after it was installed (via bleeder valves on the m/c). And, I've bled the entire system at least six times. I've got no apparent obstructions in the line, nor any difficulty bleeding the system. I've got absolutely no air in the system and absolutely no clue why I've got a rock-solid pedal with not travel and little stopping power. PLEASE HELP!!! P.S. This is a NON-power brake system.
Probably the result of mutiple problems. First could be not enough pedal ratio, should be about 6 to 1. Second would be too big a MC bore relative to the brake cylinder sizes. Those two things will work hand in hand to give you the problem you have. Best bet is to replace the MC with the same size bore as it came with. Was it power to begin with?
It was never power. 1" bore x 1.1" stroke. Regarding pedal ratio, I have it attached almost in the same spot as the stock m/c, but I'm not sure of the bore of the original m/c. On the Wilwood m/c and pedal combo's they sell, they have the rod attached very close to the pivot point of the pedal. Would it make THAT much of a difference if the pushrod was attached to the pedal closer to the fulcrum of the lever?
Divide and conquer... First sanity check: does the MC move any fluid? Disconnect the brake lines and make some loopback lines that go back into the reservoir. Pump the pedal and make sure a) you have enough throw, and b) it's moving fluid. Next, same thing, except verify there's pressure at the bleeders. Do the calipers engage at all? Jack it up, hit the pedal while someone spins the tire. Any resistance? Opposite problem: is it already engaged all the time and not releasing correctly?
Pump the pedal real hard and check to see if the brakes stay locked.. If so.. Remove the pin/bolt that attaches the rod to the brake pedal.. If the brakes release... you have the rod too deep into the master cyl. It is not allowing the fluid to bleed back into the master.. Back off the adjustment until you have about 1/2 inch freeplay in the pedal.. I hope this helps...
3 to 1 is the reason its rock hard, and a larger bore master than the wheel cyls require wont help either..on a non power setup id try to get 7 to 1 to get some feel ,assuming you have enough travel at the pedal. not sure on buicks but most mid fifties drum braked cars had a 1" or 1 1/4" master from my experience.
Also remember that originally you had a given single MC bore size pushing 4 wheel cylinders now you have a dual MC only pushing 2 cylinders each. That is another big change from original.
Another simple thing to do, before you overengineerandoveranaylize, re adjust the brakes. loosen them up so there is no drag, I had this symptom on my old chevy and loose brakes fixed it. It will lock the drums up now where when the shoes were tight it would barely stop. Frank
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