Brake guru HELP!

[Ironmike]

Hi guys. As some of you may remember I did the Scarebird front disc conversion on my 71 Demon and had some "mushy" pedal issues.
Well, all your advice finally got me a nice firm pedal.

The problem is, the car just doesn't stop very well. Might not notice it unless a green light turns yellow real fast....or maybe a deer runs in front of me. My local dragstrip has a notoriously short shutdown and it's kinda scary. In any case, I'm getting ready for the Mopar Nationals in Norwalk and I just can't run the car again until I get things "fixed".

The details are: Original 340 car with manual 10" drums up front. When installing the Scarebird kit I bought a dist block and master cyl for a disc/drum car. All new lines front to rear.
My master cyl is Raybestos MC36406, which is a 15/16 bore.
If I switch to a Raybestos MC36426 with a 1 15/16 bore, could this help the thing stop better?

As usual, I'm stumped. Nice pedal, new compononts.....GEEZ!

 

[Ironmike]

Nobody?

OK. Which master cylinder will create more brakeline pressure, a small bore or a larger bore?

 

[RedFish]

They all make the same line pressure, as much as 900 psi If you stomp it. Larger bore move a larger volume of fluid which helps where large bore calipers and wheel cylinders are supplied.
What size rear brakes do you have and are they working properly ? They should lock down with enough pedal pressure.
Scarebird uses Chevy Cailier/Celebrity brake parts that would stop one of those.
They were meant to stop a much heavier vehicle. Scarebird wouldn't recommend them for performance use. A more agressive brake linning might help.
Yes the OEM Kelsey-Hayes brakes used the same diameter rotor. The difference is in braking surface. That 4 piston caliper and pad grabbed about a third of the rotor diameter.