trying to put power brakes on my 68 gtx, have 4 wheel drum, also converting front brakes to disc from dru, can get brake , our local parts tore lists two boosters ,one for disc and1 for drum, part numbers are different and disc booster is no longer available. could i use the drum one? i cant see why there would be a difference as long as the master cylinders bolt up the same
I did a bunch of research and spent some time speaking with Wilwood, SSBC as well as several other folks that have dabbled with this subject in the past when it came time to do a power drum to power disc conversion on my 69' Roadrunner. I don't want to see anyone make the mistake that I almost made when putting all the parts together for a power disc set up
A power booster from a drum set up will not work correctly for a power disc set up. The power assist ratio between the drum and disc boosters are entirely different. Sure you can bolt on a 1 1/8" bore Power Disc master cylinder onto a power drum booster but the exponential of assist vs. pedal travel will still be incorrect.
The Power Drum booster is a Midland-Ross. The Power disc booster is a Bendix line and yes they are very hard to find. You can find some luck with finding a core on places like this or ebay and have them rebuilt, but that can be pretty pricey. I was able to find one online refurbished, only after 8 hours of hunting. I got pretty lucky and happened to get their last one. The part was = A-1 CARDONE Part # 503603.
For guys like me that want to convert power drum to power disc, obviously it can be quite a task to put all the pieces together. The main problem is most power disc conversion kits out there being Right Stuff, Summit, and others are designed for a non power to power disc conversion. The supplied power booster in their kits have bracketing to work with the original set up. The OEM power brake car being either drum or disc have different set up under the dash that doesn't work with the aftermarket kits.
If you have non power drum, you're almost better off going with an aftermarket kit. Trying to convert to factory power disc will require the correct set up under the dash (including the linkage), trying to find a booster, correct distribution block and then the spindle's, calipers and rotors. It will probably come out more expensive and will definitely be more time consuming than going with an aftermarket kit, but I guess it all depends what your main goal is...An OEM setup and better braking or just better braking
Here's a pic of a factory Power Disc booster (on left) and power drum (right) for 69's and 68's:
Hope it helps...Best of luck on your brake's what ever way you go.
