1972 corvett brakes

[bill mancuso]

i have a 1972 big block coupe the car has had brake problems for a long time . i have replaced every part of the brake system . new rotors .002 runout calipers pads several types master cylinder hoses lines . it does not have power brakes. it has a firm petal and will not stop the car with all the pressure that i can apply the proportional valve has not been looked at does any body have any ideas thanks

[Terry M.]

Re: 1972 corvett brakes

What is the casting number on the master cylinder? If it is a Delco master cylinder the casting number will be on the inbord side -- facing the enine.

[Joe L.]

Re: 1972 corvett brakes

bill-----

I suspect a possible master cylinder problem, too.

The "proportional valve" is NOT a proportioning valve, at all. Its functions are only pressure differential sensing and fluid distribution.

One thing I would suggest is obtaining a brake pressure gauge and checking the actual pressure at each corner when the brakes are applied. You can get these gauges from Stainless Steel Brakes in Clarence, NY.

[Terry M.]

Re: 1972 corvett brakes

The reason I asked about the master cylinder is if a cylinder for power brakes were installed, this would create the symptoms described.

In the absence of a Delco cylinder and its casting number, measuring the diameter of the master cylinder would tell.

[Terry M.]

Re: 1972 corvett brakes

The reason I asked about the master cylinder is if a cylinder for power brakes were installed, this would create the symptoms described.

In the absence of a Delco cylinder and its casting number, measuring the diameter of the master cylinder would tell.

[bill mancuso]

Re: 1972 corvett brakes

i have checked the master cylinder bore . i to thought it could be wrong but it is not . i should be able to slide the wheels not even close . seems to be plenty of fluid when i bleed the brakes .

[bill mancuso]

Re: 1972 corvett brakes

i have checked the master cylinder bore . i to thought it could be wrong but it is not . i should be able to slide the wheels not even close . seems to be plenty of fluid when i bleed the brakes .

[Joe L.]

Re: 1972 corvett brakes

bill-----

Even if it's the correct bore size, there could still be a problem with it. At this point, I would say that it's one of 2 things:

1) the master cylinder is not performing correctly;

2) there's air still trapped somewhere in the system, probably at the master cylinder. Did you bench bleed the master cylinder prior to installation?

[Joe L.]

Re: 1972 corvett brakes

bill-----

Even if it's the correct bore size, there could still be a problem with it. At this point, I would say that it's one of 2 things:

1) the master cylinder is not performing correctly;

2) there's air still trapped somewhere in the system, probably at the master cylinder. Did you bench bleed the master cylinder prior to installation?

[bill mancuso]

Re: 1972 corvett brakes

i have had three master cylinders on the car all the same symtons . i used my brake bleeding tool to remove the air firm petal

[bill mancuso]

Re: 1972 corvett brakes

i have had three master cylinders on the car all the same symtons . i used my brake bleeding tool to remove the air firm petal

[Dennis H.]

Re: 1972 corvett brakes

I had the same problem on my 71 manual brake car. After bleeding the brakes several times, I bought a MityVac vacuum pump. After using it, the brakes were perfect. I would have bet 100 bucks that I had it bled properly but there was still air in the system until I used the MityVac.

[Dennis H.]

Re: 1972 corvett brakes

I had the same problem on my 71 manual brake car. After bleeding the brakes several times, I bought a MityVac vacuum pump. After using it, the brakes were perfect. I would have bet 100 bucks that I had it bled properly but there was still air in the system until I used the MityVac.

[bill mancuso]

Re: 1972 corvett brakes

thanks dennis i have the mity vac and use it good tool . what type pads do you use or suggest . it has been a while sense i put them on i dont remember what i used . i work mostly on early chevrolets on some i have had to change the type of shoes to get them to stop . the vett has a firm petal no stop . thanks

[bill mancuso]

Re: 1972 corvett brakes

thanks dennis i have the mity vac and use it good tool . what type pads do you use or suggest . it has been a while sense i put them on i dont remember what i used . i work mostly on early chevrolets on some i have had to change the type of shoes to get them to stop . the vett has a firm petal no stop . thanks