I have speedway discs up front on my 36 ford. I have 56 chevy drums in rear. I have a speedway disc drum master cylinder, with a 2lb res vavle for the front and a 10 lb res vale for the rear. I had to make my own pushrod to mount the speedway master to the ch***is eng brake pedal kit with pieces of a mustang and speedways. I had it set up with a decent pedal, but the pushrod had no play in it and I would go from a good pedal to one that I had to pump to get a hard pedal, and would not stop well unless I pumped. I wanted to get more play in the pushrod so that the master would retract fully (looking into the master you can see the holes when the pedal is pushed), as it looked like I had to pull the pedal all the way up before it did before. So I shortened the pushrod by 3/16. No I get no pedal at all and it barely stops. Master has been bench bled, and never ran dry, and I just bled it now with no air from any of the bleeders with my helper using the 3 strokes and hold while I crack a bleeder. With the wheels up i can feel the drums and discs holding as soon as the peda is pushed and I cannot turn any wheel by hand with the brakes on. but pedal goes down when driving and the rear locks if I push it to the floor. It seems like the front discs are not grabbing as they should...any ideas?
You still have air in the system somewhere. After replacing a master it can be really hard to get all the air out. Bubbles get trapped and are a ***** to get out. Make sure the bleeder on the caliper is at the very top when bleeding. When cracking the bleeder if you go too far air will go right back before you tighten it. Try cracking the bleeder so that it just barely lets fluid out and only spits fluid when the brake pedal is depressed. Make sure the bleeder valve it's closed before letting the pedal up at all. I like to use speed bleeders because there is very little chance of air getting back into the system. I've had to bleed 4-5 times to get every last bit of air. If that doesn't work try jacking the rear so the bleeder is above all the brake lines in the car and then do the same on the front
Are you sure that you have the residual valves facing the correct way in the lines? You didn't say but I ***ume the master cylinder is below the floor, it may take a power bleeder to get all the air out of the system when mounted low. Good Luck! N.N.
Are the rear shoes adjusted up to a light drag? By some chance do you have the low drag GM metric front calipers? If so you will need to get the regular GM metrics as the low darg ones use a special MC. Also brake pedal needs a return spring and a solid stop so you can set pushrod freeplay correctly.
rear shoes are adjusted. I just addeda return spring. the calipers came in the speedway kit, I am not sure if they are low drag ro no I can check.
Something to be careful of is the type of friction material of the brake pads. I deal with over-the-road truck vs school bus vs cheap ******* dump trucker vs heavy short haul truck. Disc brake friction material is a like big truck brake shoe lining. Some lining likes a lot of heat and pressure to make it work, garbage truck in the city. The opposite is of a formula that a flatland trucker can use in his local haul truck and trailer. Fancy ceramic metallic and metallic brake pads don't work well with non-power ***ist brake systems in a lighter vehicle because they don't get enough braking pressure from the hydraulic system AND the heat from slowing the load. It's kinda like an engine cooling system with the correct size of radiator, thermostat, and water flow rate to make an engine run cool. Heating capacity from the hydraulics and proper friction material into the rotors or drums is what changes kinetic energy into heat energy. I'm dealing with what hydraulics I picked. I'm questioning brake pad choices I made.
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