Combination valve ??'s

**deadcarny** · 07-07-2005

I just converted the car to 4 wheel Disc Brakes from 4 wheel drum brakes. I was told that I could leave the stock Combo valve in place if I gut it out (??) and then install an adjustable proportioning valve in the line to the rears. Is this correct? What harm is there to just leaving the stocker as is? Is it because of the "residual" needed for the rear drums? It is going to be a while before the car sees actual street duty, but it will be moved around for work and the brakes will be used during these moves. will the brakes still work good enough to move it around with the stocker as is and without a prop valve??

Sponsored Links

**ertoys** · 07-07-2005

I would like this answered as well, if someone can help.

**68BNUT** · 07-07-2005

Well ive never heard of "gutting" the OG prop valve, You could remove it completly and plumb in a adjustable prop valve to the rears. Inlinetube.com sells a combo block that distributes and proportions for disc/disc aplications. If I remember right its around 100$ The reason your old one wont work is it probably doesnt even put out half the pressure that a disc setup needs.

**fuzzyonion** · 07-08-2005

You shouldn't need to gut the old drum splitter. It should be just a splitter with a warning switch, even on the 1972 4drum system. This would have no effect on pressure, residual or otherwise. It only has a shuttle valve which offsets to trip the warning switch if there is a brake failure.

The disc/disc valve being sold might be correct for your car with your brakes... but then again it might not be. It has a warning switch and a proportioning valve which is not adjustable. They are not for "all disc/disc applications" as advertised, and the sellers have no info on them except "they are for disc/disc". Different brakes and different cars need different proportioning specs. Some need none.

The proportioning valve should only operate on hard stops anyway, if you have your front to rear bias correct, so driving it in and out of the garage without one should not be a problem.

Here's some decent info on brake bias and proportioning valves, if interested.
http://www.stoptech.com/whitepapers/...ing_valves.htm
http://www.stoptech.com/whitepapers/...erformance.htm

**deadcarny** · 07-09-2005

thanks! That was exactly the kind of info I was looking for. Now I can leave the old valve alone and then put an adustable in line later! Thanks again.

**68BNUT** · 07-09-2005

I really think the old distirbution valve does have proportioning in it for drums and they take way less pressure than discs, So it may not let enough pressure through to actuate your discs brakes. imo

**fuzzyonion** · 07-09-2005

The 1972 GM drum splitters cant have any balance valving.
Metering and proportioning were each seperate pieces back when that same part was used for both disc and drum.
The 1972 drum splitter was the exact same part as the 1970 disc splitter.
(#1234388 /distributor and switch assembly, brake pipe/ for the Abody).
71+ disc cars got a combination valve, but drum cars retained the old part, which has just the shuttle valve to trip the warning light.

**tripower** · 07-11-2005

So if I'm reading the comments correctly, you could get rid of the stock valve and just go with an adjustable rear prop valve?

I'm in the same situation in that I'm converting my 65 A-body from manual drum/drum to manual disc/disc. I don't have an existing valve, so I'm going from scratch. Would I be better off going with just an adjustable valve to the rears than messing with getting something like the inline tube disc/dics valve? Thanks.

**deadcarny** · 07-12-2005

So, final verdict?
I have the vlave out of the car as of about 10 minutes ago, so I need to know if it should go back in as is or if I have to modify it somehow.
BTW, getting that thing out with the headers is a pain in the rear!

**68BNUT** · 07-12-2005

Do you need it for just moving your car around the shop no, do you need some kind of prop valve inline to the the rear, yes. I was unaware that the later models were just splitter valves. On my car it was a combo valve thats why I just got rid of mine for the inline tube combo valve.

**deadcarny** · 07-12-2005

Yeah, right now It would be just to move the car around. When the car is almost road ready I will definately be getting an adjustable valve.

**68BNUT** · 07-12-2005

Alot of guys do that and it makes the engine bay cleaner to lose that splitter and hide the adjustable somewere else. Good luck.

**fuzzyonion** · 07-12-2005

Combo valve assemblies weren't used by GM on any cars until 1971.

If you dont want a warning switch, you dont need it.
If you have a combo valve, rather than just the splitter, shtcan it, unless you are setting up the brakes to be correct for that valve assembly.

Like 68BNUT says, you can put a T in for the front, and run an adjustable to the rear. If you want a warning switch, use the old splitter.

Enter your username:
Do you want to login or register?	I want to create an account To login, enter your password:
Enter your password:
Forgot your password?	Stay logged in

Login / Register Close Panel

Thread: Combination valve ??'s

Display

Combination valve ??'s