[odin8183]

Dual Master Cylinder conversion question:
On my 1966 GMC 1500 I used a dual master cylinder and the equalizing valve and some of the tubing from a salvage 1970 3/4 ton Chevy truck. I used the core MC and got a rebuilt MC from NAPA P/N 10-1331.
I reused the equalizing valve and part of the tubing that was on the salvage truck and just separated the front and rear brakes- re-plumbing the tubing for the rear brakes to the rear chamber of the MC. I then routed new tubing to the front brakes. That tubing screwed into the front MC chamber. I bought the new steel line from NAPA. I added a simple little signal light I bought from NAPA and mounted it on the dash. It was a sinple conversion that was quickly accomplished.The braking has been fine with my four wheel drum brakes. I've felt alot safer with my truck's braking and have had no problems since I did the conversion about 10 years ago.
Caution:
An Equalizing Valve is not a Proportioning Valve!
Some confusion comes in because the early dual master cylinder trucks (example 1970 3/4 ton) had a equalizing valve with drum brakes front and rear. This valve is not the same as a proportioning valve necessary for disc brake systems. An equalizing valve just senses pressure differences, closes a circuit and will turn on the brake warning light if the pressure in the front and rear reservoir of the MC are different.

CO'T