6874BB2-11 Brake Booster Kit for 1974 Nova

[soanova]

I installed a 6874BB2-11 Brake Booster Kit in my 1974 Nova and the brake are being applied without touching the pedal. I tried adjusting the clevis pin adjuster numerous times. But the threaded rod that came with the unit is too long and interferes with the brake pedal. After much frustration I measure the length of the rod from the old, original unit that came from the factory and it was much shorter. So I cut about 1/2" off of the rod of the new unit and it seems to be somewhat better.

But nowhere in the instructions did it measure to do this. This was definitely not an issue of having to drill a new hole as there was not way the clevis pin would have been in the center of the brake pedal area. But I have no other choice as there was no other way to eliminate the brake from being pre-loaded or applied constantly.

Has anyone else had this issue?

[soanova]

CPP please reply to my question..

[CPPAaron]

Whenever a Pre-load situation happens like this you want to check the gap between the master and the booster pin. You want a 1/32"-1/16" of freeplay between the two. Also, when converting from manual to power brakes you want to run the booster clevis though the lower hole on the pedal. Generally 1" lower then the factory manual brake position. If no other hole is there then one will need to be drilled.

[soanova]

Whenever a Pre-load situation happens like this you want to check the gap between the master and the booster pin. You want a 1/32"-1/16" of freeplay between the two. Also, when converting from manual to power brakes you want to run the booster clevis though the lower hole on the pedal. Generally 1" lower then the factory manual brake position. If no other hole is there then one will need to be drilled.

The car originally had power brakes. I wanted to replace the booster, MC, and proportioning valve and chose your entire kit since it was already assembled and thought it would be a direct fit. But I am finding that it is not. Why would I need to check the gap between the master and the booster pin if this was a complete kit?

The issue I see is on the end that connects the clevis pin to the brake pedal. The threaded part is too long and interferes with the pedal and therefore I had to cut it. This is what I am asking.

[soanova]

Here is what you own instructions state...
Check Booster Pushrod Adjustment

The pushrod that actuates the master cylinder must be properly adjusted. Ideally there should be only slight clearance between the booster pushrod and the master cylinder pushrod. Interference will preload the master cylinder. When the system is preloaded, it builds pressure each time the pedal is pressed. Since the master cylinder is not allowed to fully release the pressure from the previous stroke, the system will eventually lock the wheels. Too much clearance will cause excessive freeplay in the pedal. In almost every case, if you bought your booster and master cylinder from us, we pre-adjust the booster pushrod and master cylinder for you so this is not a problem.

So the problem has to be that the rod that connects to the brake pedal is too long and should be cut to length...

[CPPAaron]

Pre-load can also be when the booster pushrod and clevis (as you have stated) are too long. Its rare but I have had to advise shortening the pushrod on the clevis side to attach to the pedal itself. Looks like you have already done so and this will free up the brakes if that was the cause of your pre-load.