power brake help needed

I have a 1936 Plymouth coupe with a mid seventies Camaro front clip and a trans am rear (w/drum) and a Chevy 1 ton van master/booster combo under the floor. I am not sure about the proportioning valve but I****ume it came from the van also.
I have fantastic stopping power, but its overly sensitive to foot pressure
It doesn't take much pressure to apply the brakes and would easily lock up if you exerted any, what I would consider normal foot pressure. Any ideas?
Thanks

 

Most one ton vans weigh about 5000 lbs when empty. Some 1 ton vans have a gross vehicle rating (GVWR) of over 9,200 pounds. That means you can put about 4,000 pounds in it. The 1 ton van's master cylinder and proportioning valve are probably why you have sensitive brakes...mismatched components. I'd install the same year Camaro master cyl and proportioning valve the front clip came from and go from there.

 

lets see some pictures of your car dude!

 

You need to get a larger bore master cylinder. It will shorten the pedal throw, but increase the force needed to push. Reducing the slave cylinder diameter will also help. I had the same experience on my OT delivery jeep when I added a booster to the stock system, had two settings off and lock.

 

What brake pedal is on it? Some brake pedal have 2 holes for the brake pushrod,some use 2 different pedals, if wrong hole or wrong pedal ,brakes are too touchy .

 

On a '60's Camaro the top hole is for manual brakes, the bottom hole is for power brakes. I converted my '68 to power brakes four years ago.

 

It has the stock 36 pedal with a reversed booster/master under the floor boards