Manual Brakes

[J-B Racing]

I installed a Manual Master Cylinder on my car that I took from 1985 GMC Full size Truck.
Well it brakes like Chit. I have to apply my both feet to make the car stop and cruise speed.
What is the best way to go!! Best Manual out there or Vacuum way?
I don't not want to go Hydro and I cannot go back to PM due to the Headers on the Stage
Motor. Any suggestions are welcome..

Thanks
Joe

 

[lrayzer]

The assumptin is made that the unit you used was from a manual brake car, with the same brake combination.
Have you changed out the Prop valve ?
I use a Wilwood with my Hydro unit 1.125" bore, but have a mopar unit on the TSO car, no problems with either.

 

[charlief1]

The master has to large a bore to work properly or it's a crappy rebuilt one. On a stepped bore master I refuse to buy rebuilt since I've had so many problems with them.

 

[J-B Racing]

I by-passed the Prop. Valve. I am direct with the front and back. When I was using the PM it was great.
I may try going Vacuum and add a Vacuum Tank.

 

[novaderrik]

what is the bore size of the master cylinder, and did you move the pushrod hole to the proper place on the pedal for a manual setup?

 

[northerngn]

I used the Mopar style master from Strange... the smaller bore version
-Dan

 

[J-B Racing]

what is the bore size of the master cylinder, and did you move the pushrod hole to the proper place on the pedal for a manual setup?

I don't remember the bore as I bought last year, and no I did not change the location of the Rod. I installed it back at the same place as it was before. it looked pretty damn straight aligned to me.

 

[Turbo6inKY]

I don't remember the bore as I bought last year, and no I did not change the location of the Rod. I installed it back at the same place as it was before. it looked pretty damn straight aligned to me.

It's not how straight, it's whether you have the proper pedal ratio. Moving the clevis further from the fulcrum will get you more leverage against the master cylinder.

 

[J-B Racing]

Are you saying if the Pedal hits the floor? Far from it.

 

[ttypewhite]

I have a brand new Mopar unit for sale if your interested.It has a 7/8 bore

 

[J-B Racing]

I have a brand new Mopar unit for sale if your interested.It has a 7/8 bore

That could be the same Bore I have. And I wanted to get that one, but I had problems finding the correct fittings.

 

[charlief1]

A truck master will have a 1" or larger bore since the brakes are physically larger than the G body ones. Pressures have to be maintained and a smaller bore has a higher pressure. The larger bore will have a higher volume but lower pressure. If you've removed the prop valve have you tried pumping the pedal repetably (sp) to see if it gets higher? If you still have drums on the back they require a residual valve to keep a certain amount of pressure to activate the shoes.

 

[J-B Racing]

A truck master will have a 1" or larger bore since the brakes are physically larger than the G body ones. Pressures have to be maintained and a smaller bore has a higher pressure. The larger bore will have a higher volume but lower pressure. If you've removed the prop valve have you tried pumping the pedal repetably (sp) to see if it gets higher? If you still have drums on the back they require a residual valve to keep a certain amount of pressure to activate the shoes.

NO The pedal seems to be pretty much the same. I found the part number I took. A Cardone 10-1889. I am trying to find the specs again to see exactly what Bore this is.

 

[charlief1]

NO The pedal seems to be pretty much the same. I found the part number I took. A Cardone 10-1889. I am trying to find the specs again to see exactly what Bore this is.

It's a stepped bore master so it will have 2 different sizes. The drums require a larger volume but the discs need a higher pressure so you'll find that it's got 2 different sizes for better braking with larger brakes. Since our cars have smaller brakes you're beating a dead horse here. Get one that's got a smaller bore and put the prop vavle back in and you should be good.

 

[novaderrik]

Are you saying if the Pedal hits the floor? Far from it.

move the location where the pushrod hooks to the pedal up closer to the pivot- you need more leverage without a booster to help you out..
i forget what kind of a pedal ratio you are looking for, but google should be able to help you out with that..

 

[J-B Racing]

Any suggestions on what kind of manual Master I should be looking for??

 

[novaderrik]

Any suggestions on what kind of manual Master I should be looking for??

one with the proper bore diameter and has the fittings in the proper side of the main body..
there are some mathematical formulas that help figure out which master cylinder to use based on tire diameter, rotor diameter, caliper piston area, and maybe even pad friction area.. there might even be an online calculator to make it simple..

https://www.google.com/search?q=bra...s=org.mozilla:en-US:official&client=firefox-a

 

[J-B Racing]

I figured out that I have a 1" Bore Master.
I have the SSBC Dual Piston Calipers in the front, and 11" Caprice Drum Brakes in the
back. Can anyone tell me by experience which Master to use before I go with a
Vacuum set up?

Thanks

 

[novaderrik]

get the pedal ratio right before throwing more master cylinders at it... google is your friend. just getting a little extra leverage on the brake pedal might make all the difference in the world.

 

[J-B Racing]

I may sound Dumb! But what do you mean by Ratio?? I don't think the Master is the issue here. I have an adjustable Regulator. I may play with that. And I replaced the front Hoses with the Stainless braided, and I found that the Holes were pretty tiny.. I think I have a pressure loss problem. The Pedal
is hard. Travels not too far down. I have no air in the system. So I will figure it out.