Just as a matter of a point, I converted my car to disks well over ten years ago and am using the original, drum booster. I've had no problems. Over 30,000 miles of driving and no problems or scares. If you can't find a disk specific booster, the drum one will serve you well.
I know a few members here are adamant about the disc power booster and I fully appreciate it
But if there others safely using the drum booster then I’ll certainly try it out
"Prior" is a brake booster rebuilder. Used to be in Garland, TX. Used to hear about them in HDTruck "circles", but they apparently branched out into car stuff. "Praise Dyno Brake" is another rebuilder, too.
In the earlier years of power disc brakes, the dual diaphragm boosters were used due to the fact that disc brakes generally take more line pressure to operate, compared to drum brakes. Hence, more diaphragm area needed. But it seems like that by about '72, even the factory power disc brake set-ups were using single diaphragm boosters universally?
I would suspect that you could use any booster/master cylinder for a power disc brake C-body up to and including the '73 model year, on a '69+ C-body car? Maybe back to '65, too? Perhaps some of the street rod brake vendors have a dual diaphragm booster that'll work?
To me, compared to a power drum brake system, power disc brake systems usually have a little softer pedal feel. But they still work good when pressed.
CBODY67
Can't help it... I feel the need to chime in here...
This is all stuff you can use math to figure out in advance. Just like the principle of multiplying force in the brake system using master cylinder piston size (x) to apply caliper/wheel cylinder piston (y)... The area of the diaphragm is multiplying force in the booster. I'll let you google your own formulas.
The reason behind a dual diaphragm vs a single diaphragm is to make the diameter of the unit smaller. If your car has a dual diaphragm, I bet there isn't room for the single diaphragm equivalent. I'm speculating that later designs were given the space for a single diaphragm of sufficient size, which bring up another theory I have...
Disc brakes require more pressure to operate, but was there a consistent engineering standard of how much force required was acceptable? IDK, maybe one of our engineer members can straighten me out here, but we've all driven different cars that had different "feel" when braking.
I am thinking the force requirements to operate the systems may be why so many folks seem to "accidentally" mix and match components and report good braking... I also wonder how their cars would compare to an equivalent factory system. I do not mean to be disrespectful or argumentative about this... but there is so much about mixing brake components that would be "wrong" and present a huge liability issue for a professional shop to just bolt in something that "fit".
I do believe those owners are correct when they claim they can drive their cars reasonably with the amount of braking pressure/force they can comfortably generate. My biggest concern for them would be if they are able to generate the full pressure they need in a panic situation. If you can't lock up the brakes with a heavy application, there is a insufficient pressure for the braking the car was meant to do... please don't ruin your tires to prove me wrong.
CBODY67, "To me, compared to a power drum brake system, power disc brake systems usually have a little softer pedal feel. But they still work good when pressed."
The reason behind this feel, is the pistons of the calipers require significantly more fluid to move into contact than properly adjusted drum brakes. In later model cars that had the option of rear discs, it is somewhat common for a tech to have done brakes on the same model with drums, and then do brakes on one with 4 discs and become concerned with the "low pedal" that they hadn't bled the system adequately. The additional travel is a normal characteristic of disc brakes.
