[frige]

I am sure this subject has been beat to death but here we go. I have a 53 chevy belair with 4 wheel discs and a underfloor power master cylinder kit. It has a fatman front suspension from a mustang 2, and wilwood discs out back. When I took it out for a test drive it has a hard pedal but does not stop very well. It has a 1 1/8 inch piston in the dual master cylinder and I took it apart, it seems ok but could use rebuilding from setting up. It does have the 2 lb check valves on both sides and a wilwood adjustable proportioning valve for the back. I wonder if it has the correct master cylinder for this setup. I looked for numbers on it but it appears to be a cheap chinese pos.
This car has been in 4 different shops over the years and I finally gave up and I am finishing it myself. I would appreciate any help.

 

[frige]

A pic.

 

[RWENUTS]

IWIKSIT!!!
I'd find a smaller bore master. Probably a 15/16 bore.
I had the same problem on my 56 chevy years ago. Went with a master sized like yours. Not good brakes. Switched back to the single pot that was a 1" bore and it was like having power brakes. This was disc/drum set up.

 

[frige]

Thanks,
That is what I was thinking. I found a site where they said the problem of a hard pedal and not stopping the car was to big of a piston. But then they started going into the math to size the piston, and I failed math.ain: If anyone can do the calculating for me I can provide the specs.

 

[RWENUTS]

Instead of waiting for some mathematical whizz to come along you could try one of these.
I have one in 1" bore. And the 4 ports are handy if you have space problems around your master.
Allstar Performance ALL41010 Corvette Style Brake Master Cylinder Mustang Comet | eBay

 

[frige]

Well, I did so much research that my head hurt. In the end it all led back to the part that you linked to. Which is the same type that is on my car now just a little smaller piston size. I found a new one on amazon with free shipping and it will be here thursday. I will post the results.
Thanks for the help.

 

[timothale]

pedal ratio

You might have to also change your brake pedal ratio for the Disc setup.