Proportioning Valve B-body Master

[Aussie81]

Hi

Ive recently upgraded my brake booster to the b-body and am currently in process of upgrading the front brakes to Blazer spindle and Corvette rotor/brake combo. Eventually I'll be adding a Quick Performance 9" with rear discs and understand I'll need to replace the proportioning valve. Is there a particular connection size required with the above mentioned upgrades, also any recommendations on which proportioning valve to purchase (fixed vs adjustable)?

T.I.A

 

[81cutlass]

I have LS1 f body fronts and blazer rear disks on my 2+2 with the B body wagon master. I would recommend keeping the stock disk/drum master and seeing how it works at first and if it doesn't work well or you feel like the rears aren't doing enough, go with an adjustable.

I went down the rabbit hole of swapping to a disk/disk prop valve and got a bad one that leaked from day one. I ended up putting the stock disk/drum back on and it has good performance.

The $20 price increase to get an adjustable prop valve to me is worth putting one in that has some control. This summit o

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[malibudave]

I would not change out the prop valve unless you need to. You should not need to when changing the front brakes out.

After you do the rear disc swap, see how your brakes perform with the stock disc/drum prop valve. If they perform normally, then your done.

The thing to watch out for, when using a stock disc/drum prop valve, is a slight drag on the rear rotor. The reason for this is that a disc/drum prop valve has a 10lb residual valve built in that holds 10lb of pressure in the rear line. This is to keep the springs that hold the rear brake shoes in place from collapsing the rear wheel cylinders. A LOT of people do not change out the disc/drum prop valve for a disc/disc and never have had any issues.

Almost all universal non adjustable disc/disc prop valves will bolt in place, but the quality of the new universal prop valves are not that great, even when you pay a lot of money for one. They seem to spring leaks.

I would not add anything to your brake system you don't need. You most likely DO NOT need an adjustable prop valve, so save your money.

Try not to do everything at once. Do one mod at a time, so if you have issues, you know it was something you just installed.

 

[oldsmobile joe]

The thing to watch out for, when using a stock disc/drum prop valve, is a slight drag on the rear rotor. The reason for this is that a disc/drum prop valve has a 10lb residual valve built in that holds 10lb of pressure in the rear line. This is to keep the springs that hold the rear brake shoes in place from collapsing the rear wheel cylinders. A LOT of people do not change out the disc/drum prop valve for a disc/disc and never have had any issues.

g body prop valves don't have residual valves. never have, never will. wheel cylinders are spring loaded. reference pic

ACDELCO 18G60 {#18031239} Gold / Professional Info Rear

 

[malibudave]

g body prop valves don't have residual valves. never have, never will. wheel cylinders are spring loaded. reference pic

ACDELCO 18G60 {#18031239} Gold / Professional Info Rear

Not disagreeing with you and you may very well be correct, but I would think that wheel cylinder spring would be to keep the wheel cylinder's pistons pushed out against the shoes with equal force on each side of the wheel cylinder. I don't think it would hold back the spring pressure of the brake shoe's springs

 

[81cutlass]

g body prop valves don't have residual valves. never have, never will. wheel cylinders are spring loaded. reference pic

ACDELCO 18G60 {#18031239} Gold / Professional Info Rear

I read the residual valves lived in the master cylinder but I never confirmed or denied.

 

[oldsmobile joe]

Not disagreeing with you and you may very well be correct, but I would think that wheel cylinder spring would be to keep the wheel cylinder's pistons pushed out against the shoes with equal force on each side of the wheel cylinder. I don't think it would hold back the spring pressure of the brake shoe's springs

thank you, my intent is to educate, not fight. i've been through service manuals for 78, 79, 80, 85 and 86 g-bodies as well as the internet. i even took one apart. i am unable to find a residual valve. i've done the c5 vette front swap and ls rear disc conversion, i kept the factory prop valve and have no dragging rear brakes. the biggest factor in a successful conversion is the master cylinder.

 

[malibudave]

I read the residual valves lived in the master cylinder but I never confirmed or denied

thank you, my intent is to educate, not fight. i've been through service manuals for 78, 79, 80, 85 and 86 g-bodies as well as the internet. i even took one apart. i am unable to find a residual valve. i've done the c5 vette front swap and ls rear disc conversion, i kept the factory prop valve and have no dragging rear brakes. the biggest factor in a successful conversion is the master cylinder.

Thanks for the info.

 

[Aussie81]

Thanks guys, looks like I'll keep the original proportioning valve and see how it performs. Appreciate all the info