hey all,
i did a front disc brake conversion on my 65 elky, the guy i got it from told me the kit was off a 70 chevelle. the problem is when i hit the brakes they tend to grab really hard as if i'm going to fly through the windshield. i changed the master on it it still does the same thing. i also installed a willwood adjuster valve on it, that seemed to help a bit but it still grabs very hard. any ideas?

You mean like they work or something :lol: Does the car lock up? Any details on the set up as far as rotors/calipers?

I don't know if this will help but I was listening to some radio/columnist mechanics discuss the same type [using parts from another vehicle] conversion you completed. Their concern is the difficulty of equalizing the brakes between the front and rear. The conclusion pointed toward numerous problems and [I believe] recommending not to do it unless using an aftermarket complete kit.

Just in case, be sure the rotors are clean and free of contamination.

I wish I had more to offer :( but I'm sure the experts here will come through.

Drive carefully!!!

the car does lock up a bit @ slow speeds it is very grabby. the bleeder screw on the calipers i noticed are metric. don't know if that means anything. i'm running a power boster on it as well. the only other thing i can think is to try a new propotioning valve. don't know if that will even help the cause. lemme know if you think of anything else.
thanks

Do the rear brakes lock up first? Do you have a master cylinder designed for a disc front/drum rear brake system? Do you have a proportioning valve/combination valve? A 1970 Chevelle would not have a metric bleeder screw.

As usual, Mrappi's questions are dead on. To cut to the chase a little more, the "guy" who sold you this kit, is he a knowledgeable mechanic or just someone who took brakes off a 70 Chevelle and sold you some components?

To help, we more info describing your system and where each component is from. Why are you running a booster?

Take care.

i believe the master is the right 1. the proportioning valve is questionable. i think that is my next move. i'll repost when i do the proportioning valve.
thanks

@ this point i'm not sure what he is. he's got a lot of cars, a big warehouse & sells parts @ a random. i know i have a good chance @ getting burned on this deal but i'm running outta options on this conversion. other than the proportioning valve i can't see what else it could be.

We don't know that yet. I reflect again on Mrapii's technical questions. The issue now is to identify exactly what you have to determine if the system will work in harmony to begin with, then trouble shoot.

For instance, if you're running the wrong Master, then no amount of tinkering will correct it until that is rectified. How do you know the Master is right? Again, why are you running a booster?

Sorry Mrapii. I don't really mean to put words in your mouth.

Take care.

i went & bought a new master from the parts store 70 chevelle w/ front disc & rear drums. the booster came w/ the kit, running it to achieve power disc brakes. i'm wondering if it is poss. i have wrong calipers? being that the bleeder screws are metric. i understand about the system working in harmony. the calipers i think are questionable. also would these calipers be off something like an iroc camaro? because i don't remember them using metric @ all in that day
thanks

When you say the calipers are metric I'll assume you're using a 10 mm wrench on the bleeder screws? If got a set of Force 10 2 piston calipers from SSBC and had the same size bleeders. When you installed the power booster did you connect the clevis pin from the booster in the same hole in the brake pedal arm or did you move it to the higher location. Could be your problem with the brakes being overly sensitive.

If you need help understanding the components go to : www.mpbrakes.com They have a pretty good section on components and their function.

One more thought. Did you change the brake pedal set. I'm pretty sure the ratio is different from your origional.

brake pedal set? not sure what set the pedal itself?

With manual brakes the pedal is about 4.5" above the floor, power brakes sit about 2" off the floor.When converting to power barkes you need to mount the clevis from the booster to a higher location on the brake pedal arm which drops the pedal height and more importantly reduces the force which will be applied under application.