I have a 69 Charger 440 car with the Hemi brake booster...disc in front/drums in rear with an aftermarket front disc single piston caliper on it..I can't seem to get the brakes to work properly. To me it seems like there is not enough pedal to stop the car..Is the rod coming out of the booster adjustable?? can I repalce it with a longer one?? or is this just not a good combo to use?? also, I have the hemi-booster master cyclinder on it...the single piston caliper is the 72-75 A-body type....If Anyone can help I would greatly appreciate it!!!!!!

If the pedal is not resting on the floor and you have braking power, then adjusting that rod will do nothing for you.

Hemi booster, does that mean disc booster?

It requires more boost so to speak for disc brakes than drum.
So if the answer is no, then you can find a dual diaphram booster, or change the master cylinder for a different diameter piston.

It is also possible that your distrbution valve/ proportioning vavle needs a change, but the above two options I think are what you are looking for.

I think that the Hemi vacuum booster is just different in the way it is mounted on the firewall.(offset a couple inches) the master cyclinder has a front pod and a back pod for the fluid. It seems like the back drum brakes are engaging but not the front disc's. could it be that i need a 72-75 type master cyclinder versus the 69 that pushed the 4piston cailper bendix type brake??

If the rears are locking up then I would consider the proprtioning valve as your problem as more likely.

Did this car come with disc or did you add them?

I would think the 4 piston caliper mc would provide even more fluid to the fronts than a later single piston caliper mc, but pressure is based on the diameter of the piston.

Yes ,this car came with front disc brakes and drums in the back...the back brakes are not locking up, but are engaging as they should..it just semms like there is no pedal left to push the front disc's. I just added the newer type replacement calipers so that if I broke down somewhere I would be able to get parts easier for them...

The fronts should have engaged first. So the rod adjustment still should not be a problem.

Proportioning valve should be good as well then.

Last thing is either the booster or the master cylinder still. To give you more assist, or more pressure.

The pedal is at a normal height at rest but when braking it is too close to the floor? In other words not enough "reserve". and they never pump up like it's an air problem? I would guess spoon the rear linings out until they are locked solid then back them off to the correct amount & if you are sure on that I would second what andrewh said - booster. EDIT I forgot about the freeplay on the booster rod,you have checked that?

Where do I check the free play on the booster rod at??? is this the rod that goes into the master cyclinder or the rod on the backside of the booster by the firewall?? How do you check to see if the booster is any good???

Could a lack of vacuum be my problem..my motor was rebuilt with a larger than stock cam...more in the size of a six-pack cam..how can you check it??

That is more pedal effort than ability to stop.
That is, you would find you need to stand on the pedal more to get it to stop than it doesn't have enough stopping power for a low vacuum problem.

You can check the adjustment for the rod. It is usually the rod that goes into the master cylinder. It should have a locking nut and the end should turn out.

I checked by looking into the master cylinder and watching to see if the piston moved when you press the master cylinder on to the booster. You can see it in the hole in the bottom of the master cylinder when it is empty or you have clean fluid.

If it moves the rod is too long and you have to back it off. Again, it doesn't sound like that is your problem.

Too long and the pedal doesn come out enought and you constantly have pressure on the brakes. Too short and the pedal goes too far down to the floor and you can't get enough braking power because it bottoms out.

Thanks for the help, I'll try out these ideas tomorrow...if anyone else has any suggestions any and all would be appreciated...Thanks Moparts