disk brakes again!
 

A couple of questions! I have a 67 C-10 with power assisted drum brakes..no proportioning valve. I just changed over to a 72 disk brake frontend with power assist and a proportioning valve.

1. Will the current master cylinder and vacuum brake booster work by adding the proportioning valve? This vacuumbooster is almost new but differs from the donor system in that it has the large flat booster whereas the 72 booster is much smaller in diameter but much thicker. Why?

2.Is it necessary to have a seal between the master cylinder and the vacuum booster?

3. Does the pedal rod length to the firewall make any difference?

I have reviewed all the disk brake threads and still a bit confused. By the way I bled the entire system and still have a soft pedal. Checked for leaks, kinks, etc. but saw no apparent problems. I did not press in on the small pin on the proportioning valve when bleeding the brakes. Thanks in advance for any anwers or advice.

Don't know about the booster, but you will need a disc/drum master cylinder.

No, but I'd at least use some RTV to keep moisture out.

Yes. Adjusted out too much (long in length), the brakes can drag due to pressure being applied on master cylinder even though no pressure being applied to brake pedal. Adlusted in too much will require more pedal movement to acheive maximum brake effort. Might not be getting full pressure from master cylinder to brakes.

Make sure to bleed the master cylinder first, then proportioning valve, right rear cylinder, left rear cylinder, right front caliper and left front caliper.

IMO, hope this helps.