I am about to do my front end rebuild with front disc conversion. have all the parts ready except for a new proportioning valve. i have currently stock powerdrums all around with a new mastercylinder and brake booster already installed. do i need to get a new front disc rear drum specific proportioning valve or can i use the current power drum one?
Definitely will need a proper disc/drum valve as the discs are a new variable in the pressure equation. If you can get a valve matching the application the master cylinder came from you'll be off to a good start, otherwise an aftermarket adjustable valve is ideal. The object is to make sure the front brakes lock before the rears in a hard-stop situation. Devon
thanks Devon. so ordering one from say Inline tube etc.. would be the ticket? or can you get a good one from say Napa? i have not checked there yet Mike
You can do a search for "proportioning" at the summit or jegs websites if you'd like an adjustable one. With some do-it-yourself plumbing it's not too hard and it's really nice to be able to dial things in for your specific build. Can you tell us about the parts you're using for your conversion? I can't really recommend an off-the-shelf standard valve, thus my comment about at least trying to match the application with the master cylinder you're using. Brake bias is a tricky item...even tire width plays a role. My job is more related to brake plumbing than system design/calibration, but I hang with "experts"! Devon
well the new master cylinder and booster were from NAPA and put in 800 miles and 2years ago. it was one of the first things i did when i bought the car and got it home as well as replacing rebuilding the current power drums. fastforward to now with a 235-70-15 front tire, 275-65-15 rear a "healthy"455, i run lighter weld wheels now, besides removing the AC car is otherwise stock weight. the disc brake setup was on a 69' Skylark I bough from 10sec455 hear on board and was complete that only had about 2000 miles on it. he went to a lighter setup. i am hoping not to switch out all the stainless lines on the fram just the upgrade to the disc and add proportioning valve now. I want to do all this in conjuction with the front end rebuild
napa and other parts houses do NOT sell prop valves, they are a dealer/summit/jegs/aftermarket only item. OPGI has them for a real good price compaired to the dealer, I think they are somewhere around $50 from OPGI and well over $100 from the dealer
Hi Mike, I recomend a 71-77 "A" body front disc rear drum proportioning valve. Pre 71 valves have another rear drum brake softening valve that delays the rear drums for an instant to prevent lock-up. 71 and later years dont need the extra valve. Dont buy the brass and aluminum ones on e-bay as they might not give clearence for your headers. The master cyl for front disc has a larger front resovour needed for disc brakes. I have a vhs video with step by step instructions and tips for rebuilding your front end you can borrow if you wish. Your neighbor Jim
If you want the Bendix or AC Delco original combo valves...I have them for sale.....$30 + ship. You will need to buy the correct mounting bracket from InLine Tube or mount the valve directly to the frame for additional exhaust/header clearance.
Mine had power drum and I never even switched the master cylinder. Left it stock with discs on front now, from scarebird. Will put in an adjustable valve in rear line, but have not done it yet. It brakes ok, but feels like front is not doing all it could. Well Duh I need to put in the valve. uzzled:
George, disc brakes need more fluid to operate correctly. I suggest you replace your drum brake master cyl with a disc- drum master cyl (the one with the larger resovour up front). It is not expensive, but it is important.
George, are yours used/rebuilt? I hate the new gold looking ones. Mine probably is still good but maybe backup would be good.
Mine are cast iron originals.....AC Delco or Bendix. I take them apart, clean them, reassemble, beadblast and paint them cast iron gray. Geoemojr, If you had a rear valve....you will make your problem worse not better. The front line from the large disc reservoir is bigger than the drum brake line to the distribution valve. The correct combination valve I have incorporates the hold-off valve.....lets the rear brakes work first...hence the name hold-off actuating the front brakes....then lets the front brakes work. Your best/correct solution for your car is to buy a new disc brake master cylinder, new line from the master to the combination valve and the correct combination valve. GM went to the combination valve in 71 for disc brake cars for a reason. Right now, your front brakes are doing all or 90-95% of the braking which is wrong.
Do you also sell the correct sized line that goes from the master to the proportioning valve?I have the same size line on the front and rear lines,also have one of those brass proportioning valves and apparently a drum master(both resevoirs are the same size)and right now my car car barely stops witha hard pedal
If you need an adjustable proportioning valve I have one for sale. $20 + shipping. http://v8buick.com/showthread.php?t=163951
Philip, Visit www.inlinetube.com and order the correct lines from the disc master to the combo valve.
Not much to the them...just unscrew the rear nut (one that goes to the rear brakes) and flush it with solvent.
