[az_chevelle]

I am in the process of adding a power booster to my manual all drum brakes, '72 chevelle for the purpose of upgrading from manual to power brakes. Got the booster ordered and anxious to start, until I was looking in a popular Chevelle restoring catalog yesterday, only to read under the power booster description, stating: "Adding this power booster to a manual brakes car does not upgrade your brakes to power brakes." What am I missing? Other than adding a proportioning valve, and hooking all the lines up, I thought I was getting power brakes out of the deal. Shall I press on and ignore this swaying statement, or is this project much more involved than I presently think? Any in put would be helpful... Thanks.

[vrooom3440]

Well it is both simpler and more complicated than that...

First adding any kind of power assist, as in vacuum booster, does make your brakes "power brakes". The booster will help provide braking power/assistance. That is the simple part.

Now the complicated part is that just adding a booster does not convert your brake system over to a power braking system. There are other differences in the overall system. Like different pedal push rod pivot points that change pedal leverage ratios. Like different master cylinder bore sizes that change hydraulic leverage ratios. These things all have to work together so just adding a vacuum booster may or may not be a good idea.

As to distribution blocks, they should not care or change. Same deal with proportioning valves since the braking force is a result of hydraulic pressure and wheel cylinder and/or caliper piston sizes. These do not change one way or another, just how you generate them.

Your brake lines can be a problem though as the booster will move the MC further away from the firewall *and* the booster brackets will put the MC at a very different angle. The booster brackets and inclined angle are required to make the pedal pushrod line up with the alternate power brake pivot point in the pedal.

[az_chevelle]

Thanks vroom3440... was wondering when somebody who knew his stuff would come up to the plate. Thanks again... MG

[engineer]

just add your booster, get a PB master cylinder and bench bleed it, your old manual one will not bolt onto the booster. Relocate the pivot to the other hole in the brake pedal, hook up to full time vacuum source at rear of carb, and connect lines. no proportioning valve required, just use your old distribution block. good to go.

[az_chevelle]

Ah Ha... it can be that simple, or at least worth the try. Thanks.

[zieg72]

Originally Posted by engineer

just add your booster, get a PB master cylinder and bench bleed it, your old manual one will not bolt onto the booster. Relocate the pivot to the other hole in the brake pedal, hook up to full time vacuum source at rear of carb, and connect lines. no proportioning valve required, just use your old distribution block. good to go.

I did it on my first Chevelle and it was as easy as described. The only word of caution is if you have a hot cam that by nature lessens your manifold vaccum you would be better off in keeping it non-power. I actually prefer manual brakes because you have better feel. My $.02

[von]

I'm getting ready to do the same thing on my '69 Malibu (manual to power drum). I have a booster, etc. Were you able to move the lines enough to reach the new MC location (approx 6 1/2" forward)? Also, some parts books list different boosters for drum and disc and some list the same booster. Do you know anything about that?

[Olle]

Originally Posted by von

I'm getting ready to do the same thing on my '69 Malibu (manual to power drum). I have a booster, etc. Were you able to move the lines enough to reach the new MC location (approx 6 1/2" forward)?

I have done that on a -71 Camaro. In my case, the lines wouldn't reach because the booster didn't just move the m/c out, the lines had to go around it as well.