Prop/combo valve with manual brakes, disc/drum setup

[Anonymous]

Sorry guys, I am a total screw up! The responses I've gotten from you all prompted me to think that I'm getting rusty and I'm remembering things wrong. I got out the old GM manual, and sure enough, I was. The combo valve doesn't isolate the two circuits, as I thought it did. I have edited my FAQ's sticky appropriately.

Apologies to all I may have confused or made angry.

Tommy

You are actually not entirely wrong. The stock proportioning valve on most cars from the mid 70's up until the advent of abs have a slider valve inside of them that will, when working correctly, shut off fluid AFTER the other half runs out of fluid. You will usually hear a small pop and the brake light will come on. Normally this will actually improve the pedal feel and you might not notice the car stoping much different if it's the rear brakes with the leak(which it usually is). If it's the front with the leak then you will have a hard time getting it to stop.

Having said that, Pretty much all masters have the fluid divided between front and rear halves. Even the single tank masters that don't look like it has a divider has a small dam inside. If you have a leak in one half or the other you will need to pump the pedal up to get a decent pedal but it should still stop the car very near the bottom of the pedals travel.

I know that I'm a new guy around here so nobody knows me or if I know what I'm talking about. I Understand that..... Just so you know I have been doing brakes and alignments as my occupation for nearly 15 years for a shop that has been in buisness since 1952. I know the stock stuff and the theory pretty well but I'm not familiar with all the different kits that the various aftermarket supliers sell. I have done a number of drum/disc conversions on 60's muscle cars though. I only post info that I have experience with.

 

[Supe]

Re: brake

supe.....................i just trew set set away that i was gonna use till i went with disc set=up... missed asking that buy a week and half.. sorry dude.!

Doh! #-o

Ah well, I'll see if I can find a set for the f150 or marquis and toss them on the Bridgeport. I can probably get them new through Currie or Moser, but it wouldn't be worth the $$$, and I've only seen them come as part of the drum brake package.


Edit: Sweet, just checked, local Autozone back home has them in stock for the f150 for $32. At least that will save me some searching.

go to the parts store and find an 11" chevy drum

What'd they come on?

If I had to change them in pairs, I'd just get it already drilled for the Chevy, but the drum on there is the Ford style with the smoother drum, whereas most chevy's I've seen have that ribbed drum. I can't think off hand what Chevy would come with 11" drums and have the 4 3/4 pattern.

 

[540Malibu]

Re: brake

Doh! #-o

Ah well, I'll see if I can find a set for the f150 or marquis and toss them on the Bridgeport. I can probably get them new through Currie or Moser, but it wouldn't be worth the $$$, and I've only seen them come as part of the drum brake package.


Edit: Sweet, just checked, local Autozone back home has them in stock for the f150 for $32. At least that will save me some searching.

go to the parts store and find an 11" chevy drum

What'd they come on?

If I had to change them in pairs, I'd just get it already drilled for the Chevy, but the drum on there is the Ford style with the smoother drum, whereas most chevy's I've seen have that ribbed drum. I can't think off hand what Chevy would come with 11" drums and have the 4 3/4 pattern.

my 89 caprice had 11" drums with a 4.75 bolt pattern, dont remember if they were 2" or 3 1/4" wide though.

 

[540Malibu]

AHA! i found it, go to advanceautoparts.com and look up rear drums for a 66 chevelle ss396, raybestos part number 2003 and 2003dgs

 

[DaveC]

Quick question. I'm probably going to order the Steel Concepts kit soon to redo the brakes. I felt alright with the s10 master cylinder on the stock 7.5, but am having reserves about using it with the larger Ford drum brakes in back.

The setup will theoretically be Steel Concepts kit, 10lb residual valve, stock front discs, big Ford drums in the back. What do I need for a proportioning valve/combo valve?

Some please set me straight here. I thought you only needed a 10# residual valve when your master was lowered. Just asking, cause I run the Ford 11" brakes with no residual.

 

[5-door]

Quick question. I'm probably going to order the Steel Concepts kit soon to redo the brakes. I felt alright with the s10 master cylinder on the stock 7.5, but am having reserves about using it with the larger Ford drum brakes in back.

The setup will theoretically be Steel Concepts kit, 10lb residual valve, stock front discs, big Ford drums in the back. What do I need for a proportioning valve/combo valve?

I have a Wilwood master, 10 lb. residual valve, stock combo valve on the frame, stock front discs, Ford drums in the rear and my car stops great!

 

[5-door]

Some please set me straight here. I thought you only needed a 10# residual valve when your master was lowered. Just asking, cause I run the Ford 11" brakes with no residual.

All I know is when I did the research for doing my brakes, Wilwood recomends using a 10 lb. res. valve on ANY drum system when doing the manual brakes. I have one on my rear drum brakes and my car stops great.

 

[Supe]

540: Thanks for the tip, I'll have a look at it, would save me some searching for sure.

Dave: With the Wilwood master ALL disc/DRUM setups should use the 10lbs residual valve for the rears.

On a DISC/DISC setup, it is required only when the master is lowered.

 

[LS6 Tommy]

First of all, welcome aboard, Fastback51!

That's what I was remembering. I knew I wasn't completely over the far edge! The funny thing is, I went back to my newer GM manual again later today, and it does have the info we're both talking about. The manual I was looking at before was from 69. It was the closest one to my couch at the time. :lol: The 1980 GM manual was on the bench in the garage and I didn't feel like going out there in bare feet.

Now I'm really starting to recall stuff about these systems. When one half of the system loses pressure, the piston on the leaking side in the master cylinder bottoms against the other "good" piston. This usually gives you the "better pedal" feeling, but it can also sometimes take out the divider seal, causing a complete fluid loss the next time the pedal is let up and pumped again. You also have to reset the combo valve after a leak. This is sometimes overlooked after making a repair and you end up with a mushy pedal and no brakes to the circuit that was repaired.

Thanks for showing me I'm not totally losing it.

Tommy

 

[Anonymous]

First of all, welcome aboard, Fastback51!

That's what I was remembering. I knew I wasn't completely over the far edge!

Now I'm really starting to recall stuff about these systems. When one half of the sytem loses pressure, the piston on the leaky side in the master cylinder bottoms against the other "good" piston. This usually gives you the "better pedal" feeling, but it can also sometimes take out the divider seal, causing a complete fluid loss the next time the pedal is let up and pumped again. You also have to reset the combo valve after a leak. This is sometimes overlooked after making a repair and you end up with a mushy pedal and no brakes to the circuit that was repaired.

Thanks for showing me I'm not totally losing it.

Tommy

Glad to be here, hope I can help someone out.

You are correct about cutting the rubbers out of the master. It's pretty common on older masters as they get the piston travel area polished over and over. So when you go outside the normal travel you can either cut or even roll the rubbers and turn them inside out. Also that's why it's important that the person helping you bleed the system only pushes the pedal half way down.