Ok so my car is a 71, but we replaced the front drums with a disc setup from a 70 SS. We used the booster, spindles, and proportioning valves but replaced front lines, calipers, slotted rotors, and added good pads.

The brakes have never seemed as good as they should be. In the past under heavy quick braking the engine would die.

I found out the master cylinder I had was the wrong year and so the pedal had to travel too far before brakes began to be applied. Replaced the master cylinder again and travel was reduced.

I still have ****ty brakes. Since winter has set in it has gotten very very bad to the point that occasionally I can push my foot as hard as I can and the car will slowly roll to a stop...never locking any wheel. Stopping distance from 45-50 is about 5 or more car lengths. But on occasion it works a little better and has enough force to kinda throw passengers forward a little but still never locks and seems inadequate.

Sorry this is long I wanted to be as detailed as possible since I've asked before and never had the problem solved.

Where should I start? Another new master cylinder? Could this be due to the proportioning block and how would I know? What else can I do? I debated better calipers in my head but that doesn't seem like it would fix a problem, just cover it.

Put it this way, the brakes are so bad that 70% of the time I can't power brake it to spin the tires...it just pushes the car forward. With enough power to spin through first gear from a stop, a burnout shouldn't be a problem...

noone?

did you pressure bleed the entire system?? sounds more like a soggy pedal...start at the master cylinder and then furthest corner..next furthest etc...Do you have a vacuum booster? or is it still a manual set-up? if its a vacuum booster, check to see that you have at least 12-15 inches of vacuum at the manifold, if its cammed at all, that might be a problem

Yes, we've bled the system several times since the brakes were put on.

We have a booster on it, but even if the booster is bad shouldn't that just make the pedal hard to push like a non-power brake setup?

The cam is just a comp 268H (.454/.454)

Thanks for the reply

Stll sounds like you have some air in the system. Try taking to a brake specilty shop and have them pressure bleed the entire system. I know this might be a stupid question, but you DID mount the calipers with the bleeder valves facing "up", correct?

As Jerry said, check to see the calipers are on the correct side and with the bleeders up. Air will be at the top of the calipers, and if the bleeders are on the bottom, it cant get all of the air out.

Yeah, they're mounted correct, been on for about a year total.

Is pressure bleeding the same as just bleeding the brakes (pumping and holding while someone opens the bleed skrew)?

I'm really sick of this, the brakes have never been working well enough to lock, sometimes even on gravel it won't slide...

If pressure bleeding is something different a brake specialist can do I can try that.

On some cars the brake pedal has 2 holes for the MC rod, one is for power the other for manual brakes.
My 70 had a button that had to be held in while bleeding, I think it was on the MC but might be on the combination valve under the rubber boot. This was rusted closed on my 78 so I had to replace the valve.
Hope this helps.

no, to pressure bleed a system you actually apply air pressure to the maste cylinder to physically push fluid through the entire system..I beleive CarCraft had an article a while back on how to make one...basically a 4x8" piece of .25" mild steel with a hose fitting threaded into it.

Thanks guys, I guess that would be a good place to start. If that doesn't cure it I suppose I could try a new master cylinder?