A-body disc conversion?

[375instroke]

I'm doing an A-Body disc conversion and am wondering about the power booster.  I've done this before on manual cars, but this is my first power brake car, and I didn't think about it till now.  I think the disc cars had a different booster.  Maybe I'm thinking about the small diameter Hemi booster.  The '69 disc master exited out the passenger side, and the A-body master exits out the drivers side like the drum master did.  I see a few different piston sizes for masters, and it doesn't look like it has anything to do with whether the car had drum, disc, power, or manual brakes.  Anyone have any insight into this?  Is there a problem using the A-body disc master with my '69 drum power booster?

[Cooter]

I could be wrong here, but I'm thinking the DRUM booster would be smaller due to the "Self energizing" of the drum brakes. Therefore, to keep them from locking up the booster was smaller. Disc. would be the larger diameter. At least that's how it is with Chevy's.

[John_Kunkel]

B-bodies with drum brakes used a single-diaphram booster, discs got a dual-diaphram booster. Discs require a higher pressure.

[375instroke]

If discs require higher pressure, why is the pedal effort on my manual disc cars so easy to press, and get the car stopped?

[chargerbr549]

Your master cylinder probably has a smaller bore most likely under an inch in diameter, usually smaller bore means more pedal travel less pedal effort and larger bore less pedal travel but then it requires alot of pedal pressure to push so then they install a booster to make it easier to push, but some people don't mind the extra pedal effort with the bigger bore master cylinders. Now for a lightweight like me I don't want to have to stick my hind end through the back of the seat and rip the steering wheel off to get it stopped.

kevin

[375instroke]

The manual master is 1-1/32", and the power master is 15/16" for a '73 Dart with disc brakes.  There's also a difference in the brake pedal leverage between manual and power, if I'm not mistaken.

[chargerbr549]

I'm not sure but i think I have heard the power booster linkage called a cantilever, somebody correct me if I am wrong. On my 69 RT Charger with factory power drum brakes the master cylinder was a 15/16 bore and when I converted it over to manual disc brakes I kept the same master cylinder but took out the cantilever setup and installed the manual brake setup out of a donor car and removed the residual pressure check valve for the front brakes as well. I guess you could experiment with several different bore sizes and see which one works the best for your liking.

kevin