whats up fellas?? i just finished my four wheel disc conversion (cpp conversion kit) ive put about 10 miles on it and now whenever i let off the gas the car comes to a stop like i was putting on the brakes and the pedal is rock hard... and tonight was the first time i hooked up a vacuum line to the booster.... i dont know if that has something to do with it or not.... any help will be very appreciated!!!:thumbsup:

Check the booster rod to master length. Chances are, its too long. I'm referring to the rod that is seen in the booster when the MC is removed. There should be clearance between the rod and the MC piston. If there is any resistance when bolting it up, the rod will not return far enough to allow the fluid to drain out of the calipers and back to the MC. Pretty common occurrence. The pedal is rock hard because the fluid is still in the calipers and has not returned.

TEST:

You can test this theory by placing a couple of flat washers between the master and booster temporarily. If this solves the issue, then gradually trim the pin until it provides clearance needed. I've seen them be about 1/16 too long, and thats enough to cause the problems you describe. Another possibility is that the rod adjustment under the dash is too tight. There should be some slack in the linkage. It should not completely taught against the booster rod.

As bob said, that was my friends problem. Wore out the pads to find it.