Rear discs & Proportioning valve

1

12sec ss

New member
I did this on my caprice long time ago, and it made a noticeable difference in braking. Caprices came with drum brakes, police cars and impala ss with discs, and proportion valve is the same on all. I tried searching, and dont see it being done on the SY/TY who are converted to rear discs. I did the conversion myself and am wondering if same would apply as my caprice, to take out the valve to have more fluid go to rear brakes...comments, ideas?

http://www.goissca.org/~gofasst/brake_proportioning_mod.htm
 
1

12sec ss

New member
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

hrmm...did I ask something stupid or just noone knows the answer? :D
 
WyoSyclone

WyoSyclone

Active member
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

I haven't looked into it yet, but could be that guys just bypass the combi valve all together when they go with rear discs..... some guys are going to hydroboost too, which changes things as well.

If and when I go with rear discs I'll probably bypass the combi and go with a manual proportioning valve, and play with it till I get the bias dialed in.
 
Daryl H

Daryl H

Donating Member
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

As nose heavy as our trucks are, I don't think we need any flat spots on the rear tires.
 
Loeryder

Loeryder

New member
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

I have read a lot about this mod and even talked to the rep at Baer about it.

GM May have not redesigned the prop valve for drum vs disk but the Baer rep told me that the rear calipers had a fluid capacity close to that of a rear cylinder for this purpose.
So that when adding rear disk to a vehicle that originally had drums the physics of the fluid would be "similar".

I want to do this mod on my Ty as well but have yet to find anyone other than the impala guys who have done it.

I am game to try it at least.
I can fell the rears grabbing (rear squats under heavy braking) in my Ty so I am hesitant to make it "worse" by grabbing too much.

Ideally, I agree a manual prop block is the way to go.
 
Loeryder

Loeryder

New member
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

So I am still not 100% clear on this mod.


The article reads like there are 2 possible mods here depending on what outcome you are trying to accomplish:
If you mod the bolt on the combi valve closest to the radiator (on the rear brake hydraulic circuit), then you are doing the proportioning modification.

If you mod the bolt on the combi valve closest to the firewall (on the front brake hyd circuit), then you are doing the metering modification.
Click to expand...

So there are 2 different "bolts" that can be modified?

Is there any other source for the "bolts" only, or is it necessary to buy a whole Combi valve just to get the bolt?

I guess I have more questions than answers...
 
Z SKI

Z SKI

Donating Member
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

Well, I will bring this thread back from the dead.

On my SS we modded both of the bolts.

We replaced the front bolt with the stealth bolt. The front bolt deals with the front to rear proportions. Stock is around 95% front and 5% rear. With the stealth bolt, that changes to 70% from and 30% rear.

Next we modified the rear metering bolt by machining off a step that is on this bolt and reinstalling it. This stops the delay in rear braking that was there to have the rear drum brakes activate slower than the front brakes. This was there because drum brakes have the tendency to lock up quicker than disc brakes.

After this was done on my car and with the addition of Baer front 13" C5 brakes, braided stainless lines all around, and with the new Baer ceramic pads the car (4200 lbs.) stops very hard.

Now for the relevance to SyTy's. I tried to do the same thing to my Sy's prop valve and the threads for the front stealth bolt are not the same and the rear bolt is also different than the SS's.

So I have done some research and found that the 90-91 1LE Camaros had a specific four wheel disc brake prop valve that I am going to try and use. I had an earlier one (87-89??) and the threads were not the same as our lines. It has to be the one from a 90-91 1LE...

Ill keep you guys posted on how it turns out..

See ya,
 
Quickstop [UK]

Quickstop [UK]

Combating adversyty.
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

Sorry to resurrect this but what did you end up doing? I am looking for a prop valve as well....
 
fauXGT

fauXGT

Brick Pilot
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

I did the LS1 98-02 Camaro front & rear conversion on my ext cab, & didn't do a prop valve.
Some of the research I found here, several of the people didn't do prop valves. I have noticed that the original "nose dive" changed to a nice squat. I guess on the LS1 change, it is pretty close to front & rear percentages as factory.:2cents:
 
Six-is-Enough

Six-is-Enough

Use to do a little Boost
Re: Read discs & Proportioning valve

Re: Read discs & Proportioning valve

fauXGT said:
I did the LS1 98-02 Camaro front & rear conversion on my ext cab, & didn't do a prop valve.
Some of the research I found here, several of the people didn't do prop valves. I have noticed that the original "nose dive" changed to a nice squat. I guess on the LS1 change, it is pretty close to front & rear percentages as factory.:2cents:
Click to expand...


X2 here. Also did the LS1 rear disc conversion with no additional porpotioning vavle work and truck was fine. Liked it so much I changed to LS1 fronts also.:tup:
 
tyndago

tyndago

New member
Re: Rear discs & Proportioning valve

Six-is-Enough said:
Here is a thread link to some 60-0 brake testing I did before and after the LS1 disc conversion.

http://www.syty.net/forums/showthread.php?t=54199&highlight=LS1+disc+brakes
Click to expand...

I have been learning a lot about stopping, the last couple years I have been involved with racing.

The tire is usually a limiting factor. The better the tire, the better you will stop. At some point, any brake that can lock the brakes up, is going to be limited by the tire.

STILLEN has some new designs for rotors, J-hooks - GT-R's some Camaro's, Mustangs. They make a little noise but have a good initial bite.

http://www.stillen.com/product.asp?id=BPSPTROTR03&c=BR
 
J

jollygreen1964

Donating Member
Re: Rear discs & Proportioning valve

I picked up a proportioning valve from the junk yard, pardon me auto reclamation facility, and another on ebay, this time I bought a master cylinder and the valve was still attached
 
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