Technical Under dash master cyl assy

I've found several 90 degree brake pedal assy for sale, they state that you can use them with manual or power brakes. Considering the ratio is different I can't see how this is possible. Has anyone used one of these that would have some input? I'm using manual, corvette style MC, disc all around, Speedways 9 inch rotor and metric caliper in the front, rears are 11.75 with GM A body type calipers, MC has a 1 inch bore. This would solve my space problems, but just by the picture I can't really tell if I could change the ratio.

 

In my 1952 Plymouth Suburban I have Wilwood brakes all around and Kugel under dash angle pedal and master assembly with power brakes. I have been using this for 7 or 8 years with no problems. I am happy with everything.

Jan in Ojai, CA

 

I have one from Kugel in my 37 , non power corvette style master, front disc rear drum . Works like a charm.

 

I'll check out Kugel. Lumpy, when you bought yours did they have a choice on manual or power brakes?

 

Mine is part # 5121. As my 37 is a 3 pedal car , The bracket appears to be drilled for both boosted and manual masters. I have no issues stopping this car ,nice firm pedal , with no excess pedal effort. I ordered this set up because I didn't want a goofy looking master set up hanging off my firewall , and I couldn't get full pedal travel with the stock pedal assy due to it hitting the back of the cylinder head.

 

Thanks Lumpy, I looked up their website, looks like a nice piece. I don't want mine on the firewall and with where my steering box is, under the floor would be a pain. I'll go with this one.

 

Might check a local salvage yard, old dodge vans had one mounted on the front of the firewall, might be cheaper option for you.

 

The key to this question of combining parts together to make a brake system work is not the method of mounting ( wether the brake master cylinder is mounted beneath the floor or on the firewall or even 90 degrees from the inner face of the firewall). It comes down to having the proper pedal ratio along with the proper dia. master cylinder.

Most of the brackets that our shop have encountered “allow” for different sized internal diameter master cylinder assembly’s. Where it gets goofy is some of the early truck bolt pattern masters that are out there (Chevy two pot truck or Chrysler single bore 4 bolt master for example). You either make a bracket to adapt from one system to the other or buy someone’s complete system to replace everything.

From what I see on the Kugel website the master cylinder that they are providing with the #5121 pedal assembly has a 1” dia. bore

The key that I have found is to properly match the bore size of the master cylinder to each system. A common problem that crops up is someone at a parts store hands you a 1 - 1/8” bore master. You install it and you cannot get a decent pedal and the brakes are “soft”.

From what our shop has found each combination of brakes ( ie; drum/drum,
disc/drum or disc/disc) has specific master cylinder bore diameter requirements.

Early drums at all four corners seem to work best with a 7/8” dia bore master cylinder.

Disc front with drums rear responds well with both a 7/8” and/or 1” dia. master cylinder

Depending on your caliper bore size at each corner of a 4 wheel disc brake system a 1” bore master cylinder is appropriate. A larger bore caliper requires a 1-1/8” bore master cylinder.

With each car/truck or whatever we work on we find challenges. I’m just trying to share what we have found.The wonderful thing is to have a forum like this to exchange ideas of what works (or doesn’t).

 

a question for the guys that have these mounted under the dash. how are you filling/maintaining them? when doing the work how are you keeping the inside of the car clean? I ask this because of all the spots on a car, the place I like to work the least, is under the dash. something as important as brakes I find silly to bury under there.

 

I fill mine thru the cowl vent , not ideal but dont have to do it often. Still beats having the master hanging off the firewall. As for mc sizing yes I usually use a 15/16" or 1" master for manual brakes.

 

Mine will have a remote fill under the original model A gas cap.

 

^^^These are good plans...compared to a build that you cannot check the level very easily...then we tend to "not check it" at all, because it is a pain.

.

 

My calipers on the front are metric GM and on the rear they are the bigger A body type calipers. I've got 2 corvette style master cyls, I've got to measure the bores to make sure but I think one is 1 inch. I was going to call Speedway's tech line and ask them since all the parts are from them.

 

Curious, but why are you running larger rotors and calipers on the rear, and not on the front?

 

It had new 9 inch on it, tried to get bigger for the front, Speedway said I couldn't get them for these spindles. I'm using a 9 inch that had the 5.5 BP, had to narrow it so I bought new axles, 4.5 BP, couldn't get drums with the right BS. Tech guy at Speedway suggested their rotors, they are like the dirt trackers run with the hat and bigger GM calipers. I spent hours on the internet researching rotors, front bearings, rear drum spacing, finally I just said the hell with it. I'm putting a adjustable proportioning valve in for the rear.