Rear Brakes Grabbing before Front

[ultramag870]

I have a 69 GTX I converted to disk in front it had manual drum set up.. I got summit sb kit and done conversion which it doesnt come with prop valve and the brakes work fine but Rear brakes are grabbing before front..(Cant do a burn out... front brakes wont hold the car..) I ordered a adjustable prop valve.. where is best place to mount this in order to adjust so front brakes get more fluid is im guessing what needs to happen. Thanks

 

[wedge69]

Mount the Prop valve beside the master and lower than fluid level. Also Did you put a Disc brake master cylender on ?
Disc calipers take more fluid volume than drums. And the front line is the one closest to the firewall .

- - - Updated - - -

You discription of your problems don't point to needing a prop valve.

 

[ultramag870]

not i did not change the master cylender.. what else might problem be?

 

[Propwash]

Your original master was set up for a drum/drum. It has residual valves built right into the master ports. I'd really recommend installing a disc/drum master, being the disc reservoir does not have that residual valve (doesn't need it, nor want it), and you will have the larger reservoir for the disc side. Then like Wedge mentioned, add an adjustable proportioning valve on the line to the rear brakes.

SSBC, Wilwood, RSD and others all set adjustable proportioning valves. Can be found at places like Summit, Jegs, and others.

 

[5.7 hemi]

I agree with Propwash!

 

[wedge69]

ME TO ! Wrong Master cylender

 

[badmopar67]

The master cylinder you'll want is one for a 70 RoadRunner which must have been available with manual disc brakes the master cylinder is m1523 I got mine from Autozone the studs might be slightly bigger diameter than what you have I just use Grade8 bolts for now but it works fine it has the same bore size as a manual brake master cylinder it just holds more fluid it has a bigger Reservoir but not as big as a power brake unit. I just checked they do specify one for disc brakes for your car but I'm not sure of the Bore size I can't check it on my iPhone but it says m1487 is for disc brakes. Ps. Just checked it out cylinder bore size is 1 inch on the M1487 that should work fine for you

 

[ultramag870]

thanks for all the info i figured i wasnt gonna get away with just changing prop valve.. but was hopefull

 

[Rocketman]

IMHO a new master cylinder will fix this problem, I too have a disc kit on the front with drums in the back.

 

[ultramag870]

im haveing trouble finding the master cylender i think i need as said earlier maybe i need to be looking for the 70 model one but all the manual ones im finding on summit are for drum to drum brakes..?

 

[Cranky]

Not only do disc brakes need more fluid, they also need more PSI and the adjustable prop valve will certainly help with that but like already mentioned, you need the proper master too. Where to get one? I do not know. If you don't care about it looking original, the newer aluminum masters for manual disc brakes from a pickup is a good one.

 

[Propwash]

This is listed for '70 GTX




http://www.rockauto.com/catalog/raframecatalog.php

 

[ultramag870]

found a manual front disc rear drum one at orielys i ordered it in gonna try it..also got prop valve from summit thanks for all the help will update results when done