DRUM brake distribution block in a disc/drum setup ??

[Kern Dog]

What is the effect of having a 4 wheel DRUM brake distribution block in a car with factory front disc/rear drum?
In theory, the effect seems to ME to be a loss of the "proportioning" that a correct proportioning valve provides.....BUT to what actual effect? Would this mean the front brakes would get too little pressure and the rears would get too much?
A friend swapped a Kelsey Hayes 4 piston disc brake setup in a '70 Dart that WAS 4 wheel drum. He retained the original 4 wheel drum distribution block. It now has a power booster and a proper Disc/drum master cylinder.

 

[steve340]

The drum distribution block will work no problem. You are right the only thing is proportioning to the rears would not be there unless you added a proportioning valve.
In theory the boosted line pressure may cause rear lock up too early. The fronts would be fine the discs need as much line pressure as possible.
Break in to the line that goes to the rears and fit a Wilwood valve and it should work out OK.
I have done this on several cars over the years and it works well and involves minimal pipe mods.
I have talked to people who say they did not fit a proportioning valve and their car was fine.
They usually are too polite to say I am an idiot and do not know much.
Generally from what I have seen, is these cars have rear brakes that are not working right or at all and they do not work that out.
Assuming everything is spot on in the rear brakes they will most likely lock without the valve.

 

[R/T]

Car rear will lock up in an emerging hiway emergency, sending the the big 70 Charger sliding sideways promting your hidden save the car reflexes as well as scaring the **** out of some asian tourists whom youve just cut off with your near miss reverse pit manoeuver.

 

[Darter6]

I've done it many times on A bodies with no ill effects. Also have done panic stops to test with very little lock up.Worked for me.

 

[Lefty71]

Car rear will lock up in an emerging hiway emergency, sending the the big 70 Charger sliding sideways promting your hidden save the car reflexes as well as scaring the **** out of some asian tourists whom youve just cut off with your near miss reverse pit manoeuver.

My brother debarked a tree that way once (backwards down the side).... wasn't the proportioning vale issue, just him...… like scraping the crap off your boot on a cinderblock. Minus one Chrysler anyway.

 

[Don Frelier]

I have ssbc discs on the front of my charger. 10" drums in the rear. With a disc/drum manual master cylinder and the normal drum distribution block. My rears will lock first but only under heavy braking. Otherwise it's a good setup.

 

[Kern Dog]

Car rear will lock up in an emerging hiway emergency, sending the the big 70 Charger sliding sideways promting your hidden save the car reflexes as well as scaring the **** out of some asian tourists whom youve just cut off with your near miss reverse pit manoeuver.

Thanks...This question was for a friend with a 1970 Dart though.

 

[Dragon Slayer]

The distribution block was the same. They just added the proportioning valve in between the distribution block and rear brakes. I know the B bodies better, but believe the A body 4 piston KH just used a proportioning valve in 70. The floating caliper single piston KH as used on B body still used a distribution block but added a meter valve for front, and proportioning valve for rear. The early cars used a 3 valve set up. Later they started to combine valves, especially 71 and up.

Bottom line is the distribution block just routes lines and has the safety switch to light the warning light if one side looses pressure (Front or rear). The meter valve when equipped, just held off pressure to the front to allow the rear drums to start activating first under light brake pressure. After a set pressure around 50-150 the meter valve had no effect.

The proportioning valve allowed normal pressure to rear brakes up to 300psi. After that it limited additional increase by 50 percent. So it your stomped on the brakes and generated 600psi in mc, front would see 600psi, and rear would see 300 plus half of 300 or 450 psi. So it was meant to balance the rear under medium to heavy braking, and save your bacon in panic or wet surface braking.

 

[chtampa]

I gutted the distribution block and added an adjustable proportioning valve.