Hi All
I finally got the 70 Chevelle on the road. I've gone through the whole brake system this spring.

I'm having trouble with the front brakes dragging/not releasing.
I had sent the booster out to be refinished "Mickey Hale".
Master to be re-sleeved "Karps".
I rebuilt the calipers and rear wheel cylinders and replaced rotors, hardware, hoses and a few lines.
When i got back from my first ride i could smell the front brakes cooking. I jacked up the front of the car and the wheels were hard to rotate.
I checked the pedal play, it seemed to be about 1/16 and the clevis is adjusted all the way in. The pedals real high and hard.

I loosened up the Master Cylinder mounting nuts a good 3/8" and tried rotating the wheels again, it only seemed slightly better but still dragging.
I see a number of posts saying the problem could be the MC rod length. I kept the MC rod that came with the car as its a disc drum car to begin with.

Are boosters all the same depth for the MC rod?
Could the MC rebuild kit be for a shorter rod?
Does anyone know the length difference for the disc/drum vs. the drum /drum rod?
Where can a guy get a shorter rod to try out?
Anything i'm overlooking?
Thanks
Dave

Any ideas?

Here is a portion of my experience with this, in case it can help you somehow:

I had a similar problem with an all-new Wilwood 4WDB / CPP master setup.
I found out that enough pressure can be maintained in the lines (to keep the disc pads slightly against the rotor to prevent "clackiing) . Once the brakes had been applied, remounting the master with shims between it and the booster did not alleviate the problem because of the residual pressure, masking the problem.
Then, I opened a brake line at the master, depressurizing the line, and that released the latent pressure on the brakes. At this point I found out that the master cylinder had been "preloaded" by incorrect length of the pushrod and the mating of the master to the booster. We're talkiing only about .125"-.150" too long, not much at all to cause the drag problem. I could have just remounted the master with shims, but it seemed an engineeringly inelegant solution. Without depressurizing the line, I might not have found this out.

Put more simply, the first step in mounting the master should be to ensure that the master will fit flush to the booster by hand, and not have to be drawn down with the nuts on the mounting studs.

The "pullback" offered to the pads after you release the pedal is due almost entirely to the torsion effect of the O-ring seals on the pistons. Think of them as rolling a little when you apply the brakes, and then tending to roll back when you release the pedal. This is not a lot of potential (stored) energy available for pullback, and even a slightly preloaded caliper (due to the preloading of the master cylinder) will not be able to overcome this with O-ring rollback.

I plumbed the master with DOT flex lines to the distribution block and rear brake line in order to remove it for valve adjustments without having to re-bleed all the time. This allowed me to remove the master and figure out the pushrod length and any issues involving the mating of the master and booster a lot more easily. Much more easily. And, there are no issues with a "soft" pedal... it's nice and firm, even pushing 16 pistons.

CPP's website has a pretty good selection of information on the booster-master-pushrod setup, including a pretty cool tool to measure all that up.

The CPP master (the MC-PV-1) has a removable insert to accommodate both power and non-power pushrods. This is also the master which has the adjustable proportioning valve for the rear brakes built in so you don't have to run an external valve. The real advantage here is that the master also has a rear pressure limiter, which can be used in diagnostics of the rear brakes not releasing as well as tuning of the rear brakes like you use the prop valve for.
In other words, there are TWO adjustments available for the rear brakes, instead of a single adjustment offered by a traditional adjustable prop valve.

This is not a commercial for CPP or its products, but through all these things I was able to learn quite a lot about the fine points of braking systems, and was able to test things out for myself.

The tech people at CPP seem to be pretty knowledgeable, and have always been willing to talk each time. This sentence IS a commercial for them, since you may be able to get some important questions answered for your own car's situation.

Good luck !

Eric

Woo hoo I have to credit Karp's http://www.resleeve.com/index.htm for helping me find the problem with my brakes. They gave me some great ideas of what to check to resolve the brakes not releasing.
The thing it turned out to be was the rod that goes between the MC and booster wasn't seating properly. The small reduced end of the rod needs to fit into a washer behind the boosters guide tube. Mine had slipped to the side and wouldn't allow the rod to fit all the way in therefore holding some pressure on the front brakes.
These guys are great.
Thanks
Dave