manual discs

[Highbanked Hauler]

   with manual discs I have heard you need a smaller piston master cylinder. Is this true??

[A383Wing]

no....master is the same whether it's manual or power...at least on mine it was....

a bigger piston in the master will give better stopping power

Bryan

[metallicareload99]

Smaller area piston will result in less effort to move the peddle, but longer travel compared to a larger bore piston.  A bigger piston would require more effort but less travel for the same amount of pressure produced

[b5blue]

73 only had manual disk master cylinder. Smaller bore, longer stroke.

[Highbanked Hauler]

 I have seen  the MC. with different size pistons in Summit. These are the 2 bolt "newer" type

[A383Wing]

Smaller area piston will result in less effort to move the peddle, but longer travel compared to a larger bore piston.  A bigger piston would require more effort but less travel for the same amount of pressure produced

I think you got that backwards...a smaller piston in the master cyl will make braking harder because less fluid is being moved

larger piston will have more fluid being pushed with same amount of pedal force

Bryan

[metallicareload99]

I think you got that backwards...a smaller piston in the master cyl will make braking harder because less fluid is being moved

larger piston will have more fluid being pushed with same amount of pedal force

Bryan

With the smaller piston, less fluid will be moved using less force.  

Larger piston will move more fluid but will require more pedal force.

Force=Pressure X Area

Smaller area master cylinder piston will require less force to generate the same hydraulic line pressure because the pressure has less area to act on.  Compared to a larger master cylinder piston that would have a larger area for pressure to act on requiring greater pedal force, but because the piston is larger, you would not have to move it as far to get the same braking effect.

[A383Wing]

a larger piston will move more fluid..the pedal force stays the same

Bryan

[b5blue]

Look at this eBay item # 390421397636. I've got one to install with my disk conversion, I'm going with what the factory figured out. 

[71charger_fan]

Raybestos MC36406 works perfectly in my '71 with Volare fron disks and Dr. Diff rear disks.

[Highbanked Hauler]

 The reason I ask is I am going to use the  79  B-body discs 12 in. rotors with a 2 bolt master cylinder. I would rather not go with power brakes.

[b5blue]

I'm using the same rotors, 11 3/4 w slider calipers. Smaller bore w longer stroke for me made sense for peddle "feel". I've heard Dak. truck masters will work.