C5 brake kit and really stiff pedal

[timopajala]

Hi, i have cpp C5 brake and spindle kit and wilwood 4 piston rear brakes on my 1967 camaro and the brake pedal is really stiff and car is really hard to brake. I have new Disc Disc Master Cylinder 1-1/8" Bore and proportion valve, i tested the booster and ist 8" dual booster and it holds pressure ok.

Do i have the proportion valve stuck or is the master cylinder too big for my setup or do i need to bleed more? Wilwood brakes uses 11" discs i think and the fronts are 13"

I bench bled the master before i hooked it up, not sure about the proportion valve how to center the thing if its not centered.

[CarlC]

The master cylinder is too large @ 1-1/8". The C5 calipers from GM are matched to a 1" bore MC.

[timopajala]

The master cylinder is too large @ 1-1/8". The C5 calipers from GM are matched to a 1" bore MC.

Thanks for the info! I ordered new master with 1" bore and try that next!

[ctcz28]

Correct, I switched to C5 front discs and also switched out my 1 1/8" MC for a 1" and brakes feel good, car stops well.

[timopajala]

Correct, I switched to C5 front discs and also switched out my 1 1/8" MC for a 1" and brakes feel good, car stops well.

So the ls3 engine vacuum is good with 8" dual booster also? I tested the booster and it holds pressure ok but i made new vacuum pipe for it to make sure.