Master Cylinder suggestion...

Working on my buddies RPU again tonight...time for a master cylinder and have no clue on what will work with his set-up..so I ask you

Here is what he has:

GM intermediate disc brake set-up up front (Speedway kit)
Early 1990's Ford 8.8 rear out of a truck w/drum brakes
Swing pedal that measure out to a 7:1 ratio
Master cylinder to be mounted on the firewall
Ajustable prop. valve in rear brake line
Line lock in front brake lines.



The truck will weigh around 2500lbs
Needs to be MANUAL brakes due to no room for a booster on the firewall.


I've been reading posts on using anything from a Mustang to a Corvette master...are these the best choices for the above vehicle??? What about ideal bore size for this set-up? Will the above pedal ratio work?

Thanks in advance!

 

i suggest the `69 Mustang disc/drum non power master cylinder

 

How about a '73-'74 Impala master for manual disc brakes? The bore would be 1".
1" is the usual size for manual brakes and 1-1/8" for power.
Plumb it so the larger reservoir goes to the front brakes.

 

A combination valve would be good too, just a suggestion.

 

Check out the Wilwood site they have many different combo's at resonable prices, plus they compact little units.Rob

 

I have been using the kit from Jegs or Summit. works really well.


Also always get the Mopar Adapter kit.

 

There's actually math out there to tell you exactly what you need.

Here's my thread on working mine up:
http://www.jalopyjournal.com/forum/showthread.php?t=438400

You want the system to pull 1000 to 1200 psi under hard braking. You need to factor in the driver and the brake system, pedal ration, etc.

Based on the 7:1 pedal and the pretty standard system configuration, you have a range of choices to factor in the driver.

If the driver can muscle the pedal and manage 150+ lbs on the foot pad, a 1" master should be fine. If the driver is a little wimpy and maybe only able to put 120 lbs on the pedal, go with a 7/8" to lower the effort. The 1.125" master is really a little large for manual brakes, unless the pedal ration is higher. It would feel like a rock on the floor.

I can spell out the math if you need it.

You should have no trouble finding a 7/8-1" master in either the Mopar or Vette style. I just grabbed a Mopar master for mine with a 7/8 piston. It was $40 at AZ, application was for a 1988 Dodge Daytona. If you want a cast iron unit, look for a vette style. Confirm the piston diameter. These styles come in MANY sizes. Also remember that if you get it together and decide the effort is too high or too low, it only requires a swap to a different size master to tailor the feel.

 

Thanks so much for all the input!!!

He really wants to go for a CAST IRON unit...Just spent an hour on Autozones site plugging in different 60's and 70's vehicles....disc/drum masters all seem to be 1" to 1.125"!

Anyone have an application for a CAST IRON disc/drum master with a 7/8-15/16 bore??? Thanks!

 

The Mid 70's Mustang II has a 15/16" bore, that is what I have on my Model A.

 

what ever you use ( i use 68 mustang) make sure it has a residual valve built in for the rear brakes or put a 10 lb. vavle in the line.

 

you will find browsing the parts much easier on rockauto.com, look for the max view button at the top right.

 

Ford Granada....7/8 bore...