im rebuilding my whole car "again" and i always had a problem with the front juice brakes in the front . they re the 29 drums with new pistions and guts and the rear are just stock chevy drums from a 87 pick up . i salvaged the master out of the donor truck that had disk onthe front . i then used the res. valves in line (10psi if i remember right) but the rear would always lock up before the front .i ran 21" wires in the front and 15" in the back and thought that was the prob so i changed to 19" wires all around and it made no diff. soo what im asking is ...if i change to an older drum /drum master will that solve my issue anyone out there that can give me advise on how to resolve this issue ..oh yea i was going to buy a proportioning valve to restrict the rear a bit more but thats prob wrong too ..help if you can please!!!!
i bought the front end from a swap and it was allready set up guy said that he had it allready to go . it might be like a 37 -48 12" backing plate mabe not my area of expertize that why im asking to see if anyone has any idea
Pull the front drums and see what the wear pattern on the shoes looks like. Where the shoes are contacting the drum will be smooth and kinda polished looking. If 3/4 at least of the lining on each shoe isn't smooth that means the shoes need to be arced/ground to fit the drum so you get proper braking. Also while you have the drums off make sure the larger end of the wheel cylinder is pointing to the front of the car,seen one than once the cylinders on backwards. Let us know what you find. Whatever is going on sounds like the fronts are not doing much of anything. Jack it up and while someone applies the brakes try turning the front wheels by hand.
thanx john and doug good info !!!i know that they were stoping the wheel when they were in the air i did that last summer but as for the wear pattern ill have to check that ..that might be it with the combination of the disk/drum master ill have to go with a drum / drum master...
The only diffs between a drum/drum and a disk/drum MC are 1 different sized resivouirs and 2 no residial checks in the disk side of the MC. As far as that goes a good share of drum/drum MCs don't have checks built into them either. The above is assuming both style cylinders have the same size bore . There is nothing magic inside a master cylinder between the 2 styles. And sickboy if you are running the 39-41 style front brakes with the adjusters at the bottom end of the shoes they MUST be adjusted by the book to work right. The 42-48 have floating anchors that take no special adjusting to work right.
If the front brakes work while the wheels are off the ground, you can rule out any serious problems.. Johns advice is right on, you need to have the fronts adjusted perfectly before you chase anything else. ( The rears have fancy , modern SELF adjusters LOL ! ) Then....if you still have a problem, an adjustable prop. valve will fix it . Dave
wow thanx you guys great advise this drum stuff is greek to me really.. i m a bike guy who got into cars on my own ..this stuff a litte more complicated than frame ,tank ,engine,wheels go!! as it is with bikes but i like to think im holing my own.... but seriously thanx for the info ill research this front end more and go with that original instinct and get that prop.valve ........give up dates later
your overlooking the fact the pistons are traveling different distances in the disc/drum mc. look at a cutaway and you will see what i mean, the disc chamber has longer bore whick is relevent to larger resovoir. that is why the disc/drum mc. won't work properly for drum/drum applications. i just went through this issue.
55Dude : Not quite ,there is a little differance in piston travel to compensate for slightly different amounts of fluid required to compensate for slightly different f/r brake types/adjustments. When you apply the brakes in a dual cylinder the rear piston hydralicly moves the front one forward untill it builds pressure,then pressure starts building on the rear half. But what do I know ,only started building cars in '60 and spent my working life in the car/HDtruck parts biz. Took more than one class on hydralics and brake systems during that time. The reason the disk side resivour is larger is the fact that as the pads wear the piston moves further out in the caliper requiring additional fluid to keep the caliper full. The wheel cylinder always returns to it's starting place when the brake are released pushing the fliud back towards the MC.
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