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Old 11-10-2012, 04:34 AM
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cobalt327 cobalt327 is offline
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Originally Posted by chevyrestore View Post
Hey guys. Got a 59 chevy truck with the classic performance power brake conversion on the frame (not up on the firewall).

My situation is the brakes work great but they always feel too hard, best way to describe it is when I hit the brake pedal the truck slows down but much slower than it should and the pedal is rock hard.

If I do a panic stop I can NEVER lock up the wheels, sometimes under a panic stop the pedal goes down just more than 1/2 way and is rock hard but the truck keeps going.

Is this a problem with the type of pad or a lack of vacuum or pushrod adjustment or what?

15-18" vacuum at idle, autozone semi-metallic pads, new brake fluid. Running the classic performance proportioning valve as well.

Thanks for any advise.
It could be several things. Now, I'm going to assume the caliper/slave cylinder bores match up correctly to the master cylinder bore since you bought this from a reputable vendor. But if all else fails, look back at this.

The pedal ratio is one thing that can effect pedal effort. But usually when going from a manual to a power booster, the pedal ratio will be such that the brakes are too touchy, not too hard. But it's still something to consider, especially if the pedal assembly is different from stock or has been modified.

The most likely cause is a too small booster or not enough vacuum. You said you have 15 to 18 in/Hg vacuum. Depending on the booster size and type (dual or single diaphragm) and the actual vacuum, the range you give goes from borderline not enough (15") to enough (18"). This also depends on what you are using: disc/drum, disc/disc, or drum/drum. If you can give more info on your set up and the diameter of the booster and whether it's a dual diaphragm or not, this could help diagnose it.

Last edited by cobalt327; 11-10-2012 at 04:44 AM.
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