I sawpped my drum rear out of my 91 Z28 for a rebuilt 88 J65 disc rear. I did the recall on the calipers, and still have little holding power on the brakes, and the pedal goes 3/4 of the way to the floor before they grab....

Car has all new:
lines
pads
rotors resurfaced
solo bleeds
system bled with 16 oz of fluid thry gravity and 16 oz mity vac bled.

Is there a difference in the booster, propotioning valve, or master cylinder between the drums and disc's? Maybe this might be my problem

I did a search and low and behold all of the things that guys are saying to be potential things to look for have been done. Maybe if there is no difference in the booster, propotioning valve, or master cylinder just try to bench bleed the old master then? I would like to not replace everything from the master cylinder all the way to the calipers....even though I am half way there.

And another question. When you bench bleed the master cylinder how do you keep fluid from going everywhere when installing it?

 

Adjustable prop. valve is an absolute must!

 

That seems like a band aid fix at the moment though. I still won't have the firm positive pedal feel after that, though the brakes might grab better in the rear.

 

The drum combination valve holds off the front brakes until the shoes have overcome spring pressure! If you switch to discs in the rear then there might not even be enough volume to drive the discs effectively. This would hold off the front brakes untill fluid pressure built up.

YOU ABSOLUTELY MUST GET RID OF THE DRUM COMBINATION VALVE AND GO TO AT LEAST A FACTORY REAR DISC PROP VALVE, EVEN BETTER AN ADJUSTABLE PROP VALVE!

 

The guy I bought the rear end from has the correct prop. valve he's giving me. I'll install it and let cha know how it turns out....

 

I switch my drum rear to a disc rear a few months ago. The year of the camaro that I got the rear out of was a 1990, but I think the rear came from a diffrent year. My question is does the year of the prop valve have to be the same year as the rear end, or are they a one size fits all set up?

 

Matching the year of the rear to the Prop valve is the best way to get factory performance. I would personally just install an adj. valve and be done with the brakes. Nice thing about the adj. prop valve is that as you upgrade your suspension you can change your braking characteristics to match your needs.

 

i'm switching my 88 drum rear for an 89 pbr disc rear this summer. what prop. valve will i need to avoid this problem in the future? The original one isn't available so where can i buy teh adjustable one? or should i just stick to finding one from a car with pbr rear?

 

Bear Brakes or Willwood sells an adj. prop valve. Try Summitt for Willwood and the Bear website for their valve.

 

ah found em, are these prop valves direct replacements to the stock pieces or does something else have to be done to muont them properly? Does anybody have pictures of how they've moutned theirs in the car?

 

theres a short tech artical about it here:
https://www.thirdgen.org/newdesign/tech/propvalve.shtml


i just wish someone made bubble flare to double flare adapters

 

Their are metric to standard and vise versa brake line adaptors at your local auto parts store. When I mounted my adj. prop valve I threw out my factory combo valve and replaced everything from the master cylinder to the factory brake lines with standard stuff. Meaning that I left the metric brake lines (on the subframe and rear axle housing) in place and adapted the standard stuff to the metric lines. I just used metric to standard adaptors on the master cyl. and standard to metric adaptors on the factory front brake lines. The front factory brake lines are tricky though because you have to use a double metric female with a metric male to standard female. The only catch with the rear is that you have to plumb the system all the way to the rear hose with standard stuff then you can adapt into the metric hose using a standard female to metric male. Also, the rear brake line diameter must be changed to a smaller diameter (3/16" I believe) but that is ok because the hole in the rear brake line is smaller than 3/16" even though the factory brake line is like 1/4" or so, go figure.

 

i'm an idiot. for as long as i've been on this site you'd figure i'd know about this already. sorry about that guys and thanks for the heads up mrdude