68 Camaro factory manual drum/drum car...Converted to power front disc brakes with new master cylinder, booster, proportioning valve, S10 style calipers. Rear brake shoes, wheel cylinders, drums and hardware are new. Rear brakes are dragging/partially applied...Car is driveable and stops good (other than brakes dragging) but pedal is sensitive. Rears will lock up very easy...E-brake has been disconnected...Proportioning valve is the same one I've used before (sold by Rick's and a thousand other places)...Any ideas would be appreciated.

Both rear wheels locking up or just one?

Both lock up and both are dragging/partially applied...

You could have some air that is expanding and causing it come on when it heats up. You could have the kit with too long of a rod from the booster to the master, in that case add a washer to each side of the back of the master to shim it out a lil, if that seams better add another till its right. You would then know how much to trim the rod. Or you could have the rod from the pedal to the booster in the wrong hole on the pedal. Or mabe the rod from the pedal to the booster is adjusted too long. The pedal should just touch the stop bumper without hardly any preasure at all just enough to hit.

So far I have come to the conclusion that the shoes are on backwards...I'll correct that and see what I get. Thanks

Rear brake hose (from frame to rear axle) was bad. This fixed the problem...

I have the same problem. You mentioned you thought the rear brakes were on backward did you try changing these? Did it help. On my car it seems that the rear brakes drag, but once you step on the brakes a few times the problem goes away. But then it comes back. Any ideas would be appreciated.

Jerryt

I had this issue and it was that the rod from the power booster to my master cylinder was just a hair too long.

I shimmed it out w/some washers until the issue went away and then used my grinder to take just the length of the washers off the rod and then put it back in w/out hte washers and I was fine.

I should have known something was wrong when it was so hard to bleed the brakes. but couldn't really see the issue until I got the car back on the road.