I recently had a 350 motor with a large cam from a 1969 corvette installed into my 1977 corvette at a corvette shop here in Tampa Fl. The brakes haven't felt right since I had it installed. I took it back to them and they installed new front brake pads and bled the brakes. that made no difference. So yesterday I bled the brakes myself again, which made no difference. So I then replaced the master cylinder and bled them again, with no change. Do you think that the problem could be the brake booster? I was thinking that if the booster were to go out it would just be harder to push the pedal. but the pedal is soft. Please help. Thanks Tim Miller

 

Was the correct bleeding sequence used? Sounds like air in the brake lines. A pressure bleeder works best. How is the vacuum, since the cam change, headlights work properly or the same since the cam swap?

 

Lets look at this in 2 steps.

1. With the car off. Press and release the brakes until are vacuum assist is bleed out. Your brake should start to get hard rock and hold pressure pushing and not slowly sink to the floor. If you cannot get a hard rock feeling here you have air in the system. This is most likely if you have bleed a lot of fluid air trapped in the caliper pistons or air in the Master cylinder. To release air in the caliper pistons you will need to push on the pads to push the pistons back into the calipers.

People will ask did you bench bleed the master cylinder ? but before you try this again read this, it could save you time and effort.


To bleed the master cylinder while connected and on the car read this.

https://www.corvetteforum.com/forums...-cylinder.html

until you get a rock hard pedal here forget about step 2.

2. Next test the vacuum brake booster. Disconnect the hose and test vacuum at 2 locations. Before and after the check valve. You should be able to hold vacuum for a good hour. If it does the booster is fine.

Next press and release the brakes until all vacuum assist is removed. Keep your foot on the brake and start the car. Your pedal should start to go down and become hard again. If it doesn't and still is soft have someone check the hoses that go from the calipers to the brake lines to see if they a expanding when you press the brakes. This will also give you a soft pedal feel.

If you get a rock hard pedal with some pedal travel but while driving it seems you need to apply a lot of pedal pressure to stop the car, it may be the type of pads used, or rotor glazing or the rotors may be too thin / worn. I think 1.21 is the minimum thinkness.

Read my old post on the effect of different pads used on my 78.

https://www.corvetteforum.com/forums...8-results.html