66 hard brakes

[Verle R.]

I have run across two cars recently (not mine), a 66 BB coupe and a 66 small block convertible. The both have a hard brake pedal, not spongy, and do not stop well.

The convertible has a completely redone brake system within the last three months, new calipers, rotors, hoses, master cylinder and booster. The hydraulic pressure at the caliper will reach 1200 to 1400 psi only with two feet on the brake peddle and really bear down. Stopping at a stop sign is an exercise in anxiety. The engine is a stock small block that pulls about 17 or 18 inches of vacuum at idle.

I don't know the whole history of the BB Coupe brakes. Everything looks good, clean. The new owner said the brakes were redone within the last couple of years. It does not have a vacuum booster. It appears to be a stock 390 HP.

Both cars exhibit the same brake characteristics, hard peddle and don't stop well.

I welcome any suggestions for trouble shooting these problems.

Thank you,

Verle

[John H.]

Re: 66 hard brakes

Verle -

I'll bet you a dime to a donut that both cars are wearing semi-metallic or "race" pads that some people think Corvettes need to stop. Almost nobody "markets" plain ordinary organic replacement pads any more ("Racers" will pay for the latest "High-Performance" stuff in the 4-color ads, don't you know), although they're available anywhere. My '67 (manual brakes) exhibited similar symptoms when I got it, and I found semi-metallic pads on it. Swapped them out for OEM organic pads and the problem disappeared.

[Dick W.]

Re: 66 hard brakes

The AC DElco 17D8 pads work very well for street driven Corvettes. I sold and installed these for years with NO complaints.

[Verle R.]

Re: 66 hard brakes

Thank you for the responses.
I will get the chance to look at the convertible in a couple of weeks.

Verle

[Don O'Grady]

Re: 66 hard brakes

I had the same problem, I replaced the master cyl, rotors, calipers, Pads, lines, hoses, Vaccuum canister. I had no leaks. I did have a short pedal stroke about 1 1/4" And had the same problem. I must have bleed the brakes 5 times. After putting up with it for all most 2 years. I replaced the new Vaccuun canister with another new one, took the car for a test drive and dumped everything on the front seat onto the floor. I still don't know what was wrong with the vaccuum system, but I now have great brakes. I would first check to make sure the check valve is working, then check the canister. Good luck.

[Verle R.]

Re: 66 hard brakes

Don,

We did check the canister. Pulled a vacuum on it with a vacuum pump and it acutated properly. Tested the check valve and it held vacuum for about 20 minutes.

Thank you for the suggestions.

I welcome any further suggestions or ideas.

Verle