i am racing a 1978 camaro and just installed 12" disks in the front and a ford 9" floater with disks in the rear and i have no brakes... I have tried a camaro and a corvette master cylinder to no avail, the rest of the guys at the track are using a grand caravan master (we have to use a oem part) and it is working but they do not have disks in the rear. i have also installed a 2# residual valve and a brake bias lever but still when i hit the brakes the first time the pedal goes to the floor, i only have brakes after i pump them up. I have bench blead my master and ran around 1.5 gal. of fluid to bleed the brakes. i only have brakes when they are pumped up. Maybe a master off of a new truck or car with 4 wheel disk brakes? any help will be appriciated. thanks  

I think you've got something else wrong here. Considering that in 1965 the Corvettes had four-wheel discs and the master cylinder at the time could handle heavy racing duty, the master cylinder for a '78 Z28 should be able to handle four-wheel discs.

You're not seeing any leaks from the calipers? No line leaks?

Once you pump the pedal and get pressure into the system, does it hold pressure or eventually does it bleed off and you have ot pump the system back up again?

You could try a heavy truck master cylinder and see what that does. But I've got a hunch there's something else going on with your brakes.  

You need a master from a vehicle with disk brakes all the way around. Disk masters work differently than drum masters which will not keep the caliper's piston in place so you have to pump them up everytime.

The system needs to be split front to rear just as done for the street. The rear might take some tweaking so don't get rid of the residual valve and bias lever just yet.

Bogie  

Like i said up top i've used a new corvette master, but i am almost believing that all of the masters that i have tried to use come oem with a brake booster and i am not running one. i dont have the room without moving the hydrolic clutch assembly. is there a manual brake assembly for four wheel disks? could i use a smaller booster off of a small car and fab a rod and a mount to make it work? the problem that we have found is that racing on a half mile track we carry a ton of speed into the corner and a little too mutch pressure on the brakes will lock them up. for the most part we only use about 20-30% of the rear brakes  

I think I found your solution. You need to get a master cylinder for a '79-'81 Trans Am with the WS-6 package. These cars had four-wheel discs from the factory, so this should solve your problem, and fit nicely in your Camaro.  

thank you will see if it works.