I have a small problem. My brakes on my '74 coupe are very spongy/sorta work/petal goes to floor. I was driving today and that was the case. Tonight I bled the front wheel calipers and put new brake fluid. This helped a little. I know there has to be air or water or something in the rear lines because I still dont have a dead stop. Gonna bleed those in the morning. The motor is not original and has a very big cam. The Holley carb is vaccuum secondary. Someone said I will never have good brakes with this combo. I never knew that, could it be the problem, or part of it? When I hold the brake and rev the motor, the pedal travels down a bit as I rev. ?????? The seatbelts are stuck and do not want to come out. They are stuck in the real that is right beside the door sill. any hints? thanks for the tips
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Re: c3 brakes and seatbelts
When you bleed the rear calipers, two bleeder valves per caliper. If you get your full pedal back after bleeding you will continue to have this problem unless you correct the reason for air in the calipers.
If your rear discs are no longer rivetted to the rear spindles you should remove your rear wheels and put a few lug nuts on backwards to secure the disc to the spindle and using a dial indicator check the lateral runout.
You can also observe the brake movement to witness the lateral runout somewhat. If the brake pads are moving with the roatation of the brake disc this is probably why you would have air in the rear calipers.
It is my opinion and experience that the best way to fix this is to have the brake disc rivetted to the spindle like it was delivered from the factory. The facility I used was Bairs in PA.
Something to reason, the LT-1, the 350/350, and L79 Corvettes could be ordered with power brakes. The LT-1 350/370 also had a Holley carb with vacuum secondaries. The LT-1's cam did not produce a lot a vacuum either and the GM engineers allowed this car to be built with power brakes.
I have a ZZ-1 350 in my 70 and I have power brakes. My original engine was a 350/300 that produced plenty of vacuum for the brakes and I see no change with the high performance ZZ-1 GM crate engine with its cam. -
Re: c3 brakes and seatbelts
Hello, When i rebuilt my 70 350 chevelle motor in my iroc-z i put in a magnum comp cam in 280 duration 486 lift and when i went to drive it the power brakes did not work at all because it produced hardly any vacume. I bought a vacume brake canister from summit racing and it cured it. It stops really good now. My 72 vette has a big black vacume canister underneath in the drivers side wheel well that i think is original since the car uses vacume for the headlights and wiper door. If yours has this it should be ok. After you turn the car off pull the vacume brake hose and it should still have pressure or maybe it is leaking out from a bad power brake hose. EricComment
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