cant figure this out?!

[nasty72nova]

I have four wheel (corvette) disc brakes on a 72 nova. They are single pistons in the rear. Dual pistons up front. I have a 7/8 bore wilwood disc/disc master cyl. I bench bled the master, bled the system several times and have zero leaks. Double and triple checked every fitting. I get zero air from any of the caliper bleeders. The problem is that the pedal feels too easy to push and if im sitting still i have some brakes. By the time I get to the street (50ft) the brakes fade away and the pedal goes to the floor with the first press of the pedal. What could cause this? And why is the pedal somewhat hard when im sitting still?

[MrQuick]

Sounds like you still have some air in the system. I usually run 1 1/8" masters with C5 brakes. From my experience a smaller master will give you a soft pedal.

[vette427-sbc]

^ Hes running a manual brake setup

[andrewb70]

Sounds like air to me as well. However, the 7/8" bore is pretty small and won't push a lot of volume. The older calipers tend to need more volume than the newer multi-piston calipers. I would keep bleeding it until you are sure the air is out and if that doesn't help, you may have to step up to a 15/16" bore MC. They can be had cheap from most auto parts stores. Another option would be the S10 manual MC. It is a quick take up design and will move a lot of fluid and provide good pressure. The problem with it is that it has a shallow hole in the back of the piston and you will have to come up with some sort of rod retention method. I used to use this MC and it worked great, but I was paranoid about the rod falling out and then I switched to the 15/16" that has a deep hole and a clip to retain the rod.

Andrew

[nasty72nova]

I actually just did something similar. I grabbed a manual 1 inch bore from a 70 vette. Just waiting on an adjustable push rod from jegs. It was only 40 bucks from autozone. I bled heck out of those brakes. Must have cycled the fluid through 10 times. I think the master waster not pushing the volume or was defective. Ill be sure to post the results.

[Wagonman1967]

Yeah Nasty, just ordered a 70 Vette New from Nappa , be in 8am. Will post as well.

[nasty72nova]

Are you having similar issyes

[nasty72nova]

Well I installed the 1" 70 vette MC. Everything bled easily and my pedal is perfect. Have to test drive but it stopped well pulling in and out of the garage. So much for Wilwood having the best stuff.

[andrewb70]

Well I installed the 1" 70 vette MC. Everything bled easily and my pedal is perfect. Have to test drive but it stopped well pulling in and out of the garage. So much for Wilwood having the best stuff.

I wouldn't exactly blame Wilwood. You went from a 7/8" bore MC to a 1" bore MC, which was better matched for your particular combination.

Andrew

[nasty72nova]

I should have been more clear. I called wilwood tech line and they talked me into the 7/8 bore. I was ready to do the 1" bore. I'm not blaming them entirely but I'm certainly not buying another one of their MCs