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Old 07-03-2006, 09:02 AM   #1 (permalink)
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adjustment to prop valve for 4 wheel disk brakes

Hello all, this is what I got: 1978 CJ5, dana30 front and dana 44 rear,35" tires with a YJ booster and mc going to a stock CJ proportioning valve to front stock Dana 30 disk braks and rear dana 44 elderado disk brake calipers. NOw currently the brakes couldnt lock up a Yugo. I hate them and it worries me. I have now read that using a 1978 Mercury Marquie that had hydroboost with 4 wheel disk brakes will help improve the braking. Now what do I have to do to the stock propotioning valve. Do I need to remove it completely, get a T block for the fronts and a adapter to connect to rear and then add a Willwood adjustable valve just for the rears? Or can i leave the proportioning valve in and remove the round black seal on the pressure metering valve. What should I do?
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Old 07-03-2006, 11:00 AM   #2 (permalink)
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I dont know about the black seal and the marquee stuff, but when you redo a brake system drum to disc you need a few new items to have the best performance out of the system. the wilwood website and a few hot rod websites have tons of info about it.

Basicly, you need a master cylinder that supplys the correct volume to the disc brakes, which is (usally)diffrent then drum brakes. Aka, stock master cylinders somtimes work depending on the bore/stroke. Bore size dertermins line presure(assuming fixed pedal ratio's and stroke of corse). You also need a new residual pressure valve. Drum is 8 lbs, disc need 2 lbs(usally). With a 8lbs valve on a disc setup, your brakes will drag just like the pedal is applyed all the time a little bit. A metering valve allows a diffrent ammount of pressure to apply to the rear brakes first, then the front. This is very important because it keeps the vehicle braking in a strait line. Disc brakes take vastly diffrent pressure then drums, so this needs to be changed. And, as you know, a new proportioning valve that determins how much braking force is applyed to the rear brakes vs. the front after the metering valve is overcome.

The aftermarket makes new combonation valves with all three of these valves in them that are adjustable, and even have a brake switch on them for that idiot light on the dash. You can buy these individually thorough any aftermarket brake company that builds quality stuff. my .2
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Old 07-03-2006, 02:17 PM   #3 (permalink)
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I used the Marquis MC and now my rear 35s lock up no problem. This is on 44s front and rear, the front has chevy truck calipers and the rear uses Monte Carlo calipers. This set up has givent me some pedal too. I had to install 1 washer between the Vacuum booster and MC (so the snap clamp will open and close) (more washers= less pedal) I also used new hard lines from the MC to the combo valve. I pulled the O ring out of the combo valve but have a Willwood Prop valve that I have not used yet.
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Old 07-03-2006, 04:48 PM   #4 (permalink)
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Get an adjustable one at Summit for $39.95. This will handle any weird combination of front/rear brakes. All you have to do is have the patience to adjust it to where the rear brakes don't lock up before the fronts.
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Old 07-04-2006, 09:29 AM   #5 (permalink)
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I'm with Jarvisjeep onthis one. An adjustable proportioning valve will solve your rear brake lockup problems, but will not correct brake drag in the rear. Ditch the adjustable and buy a combination valve designed for your type of application such as the ones from Master Power, Vanco, etc.
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Old 07-05-2006, 03:40 AM   #6 (permalink)
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Quote:
Originally Posted by resqme
I'm with Jarvisjeep onthis one. An adjustable proportioning valve will solve your rear brake lockup problems, but will not correct brake drag in the rear. Ditch the adjustable and buy a combination valve designed for your type of application such as the ones from Master Power, Vanco, etc.
Uh-huh.

A combo valve (often mistakenly referred to as only a "proportioning valve") actually performs three functions. Do it right and get the right valve.
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Old 07-05-2006, 09:05 AM   #7 (permalink)
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Quote:
Originally Posted by LilRocky
A combo valve (often mistakenly referred to as only a "proportioning valve") actually performs three functions. Do it right and get the right valve.
I didnt know people refer to a combo valve as a proportioning valve. lol. THAT explains alot of the posts on here..
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