Disk Brake Help.....

[myoldchevytruck]

I recently swapped to disk brakes in the front of my 69' SWB. Yesterday, I was informed that both the Master Cylinder and the Proportioning Valve needed to be changed. Are there specific years that I can pull these parts from? Say, 71-87. Or can any GM setup work that has disks in the front and drums in the back. (P.S. - the later models are readily available here in So. FL where the early models are scarce, unlike the Southern States or the Mid West) Thanks, Harry

[70c10]

Got my prop valve used from a 71' and new MC for 71' also at Autozone.

[70GMCer]

I would say that any GM disk/drum prop valve from trucks would work. I think that the 3/4T ones maybe be different. I'm using an 84 burb MS with a 71 prop valve. Others will chime in here.

[myoldchevytruck]

ttt

[Longhorn Man]

I would use a master cylinder off a 71 or 72, this way you know it'll bolt right up. I'm willing to bet you could get a prop valve off of tthe parts board for 25 bucks or less.

[michael bustamante]

yeah you have to change the prop valve but I heard you have to change the brake lines too from the prop valve to the caliper. Ill lbe watching this to see if someone can confirn this

[SCOTI]

Any pre-81 GM 1/2 ton truck master cylinder & prop valve would work. Some later models (81-87) might have the GM 'quick take-up' valving & might be more sensitve to swap.

If you don't want to mess w/brake lines, you can also use the hard-lines for the later model trucks w/a little tweaking by hand. I used a 73-78 master cylinder, hard-lines & prop valve combined w/a 71-72 power booster (& 71-72 related firewall brackets). The 67-72 prop valve mounts up by the master cylinder; the 73 & later prop valve mounts on the splash apron that is between the frame rails in front of the balancer.

I grabbed a master cylinder, hard-lines, prop valve, rubber-lines w/retainers, & the brake line that exits the prop valve for the rear brakes off of a 75 donor 1/2 ton truck. I made sure to leave that rear line exiting the prop valve as long as possible.

I mounted the prop valve to the splash apron on my 68 just like it was mounted on the 75 donor. The front hard-lines line up w/pre-existing holes in the frame (even though my truck originally had drums on all 4 corners the holes were still there). I used new 73 & later rubber-lines & secured them to the upper a-arms w/factory GM retaining clips (the reason I grabbed the donor rubber-lines was for the GM retaining clips). The lines route to the calipers just like any disc brake truck.

The rear line spliced into a factory union block that already existed under the pass side of the cab. I simply cut the line to the required length using a standard tubing cutter, flared the fitting properly (dbl flare), & secured it to the union after removing the original line.

The hard lines from the master cylinder to the prop valve required very minimal 'tweaking' to accurrately follow the frame rail for a factory correct appearance. If you need any more specifics let me know . . ....

[tcb-1]

like Longhorn Man siad, run to a parts store and pick up a 71-72 master cylinder. I then bought a CPP PV-1 proportioning valve. You will have to bend and flare some tubing here and there, but it well worth the effort.

Buy a good flaring tool!

here's my setup on my '69. No power booster and she stops on a dime!