Master Cylinder

[pasadenajim]

I have a 65 K1500 with the power brake booster from the factory. I would like to go from the fruit jar master cyl to a dual reservoir ... anybody have any experience in making this change? IF so, what brand or part number and what might I have to do to make it work properly?

[AZKen]

Jim, until someone who has actually swapped a single for a dual, here is a post. It may at least help with the plumbing issue and may give a part number to check out. It says 67-70 Impala. Also check 67 truck dual master, drum/drum.
It's all about the reservoir mounting hole spacing and rod lengths (the intermediate rod)....and of course the plumbing.
As you know there are many complete kits available for about $350. If you read up on all of them, they may give clues to what they are using.
All info I found is for Chevy, don't know if GMC is same in that area. Probably is.

[AZKen]

From the web, Not verified. I added the O'Reilly's link.
A complete matched set, part number 50-3715, Al Cardone, 1967 C10 Truck. Orielly auto a bit over $100. Have it on my truck.

Or if you already have the Cardone Master Cylinder for 67 C10/Impalla Dual Drum Drum Manual $17 at Oreilly (Part # 10-1329) then just add the following booster (Cut off the eye on the pushrod and sleeve or weld it to your adjustable brake pushrod under the dash)

Part number 54-73709.

Make sure you redrill the brake pedal 1" lower (3/8" hole) and remount the rear of your pedal push rod/readjust for 1/8 to 1/4" free travel. The free travel ensures the master piston ports are uncovered for the return stroke.

Lowering the rear of the pushrod on the pedal changes/lowers the brake ratio from factory manual ratio to factory power ratio.

It will give you firmer pedal at the top of the stroke and more modern feel without the grabbiness of the higher manual ratio. Otherwise your brakes will be very touchy even when properly adjusted with the rears locking at the blink of an eye)

No proportioning valve is requried on Dual Drum power brakes. I adjust the rear for a bit less drag than the front and although sensitive, almost never lock the rears, even on wet roads with panic stops.


Naturally you'll split the lines so front and rear are fed by their own resevour at the Master.

The 67 C10 master has equal size resevours.....power disc/drum has a large resevour and a small resevour, wrong part for dual drum application.

The line running to the rear along the frame is 3/16 all the way back. In the conversion, simply run a 1/4 line all the way back and install short length of 1/4 to 3/16 adapter line at the top of the rear rubber line. You can then run the factory 3/16 lines between the rear distribution block and the rear cylinders.

This is an under $350 upgrade with all parts from Oreillys (hoses, cylinders, master, booster, lines and fittings) and represents probably the best money you can spend on your squarebody.

The resevour next to the fire wall is plumbed to the front drums on one circuit.

The resevour furthest from the fire wall is plumbed to the rear drums on a second circuit.

The adapter fittings you will need to plumb the two lines to the master are avaialble at oreilly.

The al cardone master has the valves in it that prevent the wheel cylinders from weeping when parked, plus the master is mounted high so none of the valves needed to hold a slight line pressure are required as when you install a master down on the frame at or below the level of the wheel cylinders.

Fully bleeding the system from totally dry can be a huge bear. I used vacuum, pressure and finally just relied on good old gravity and lots of pedal pumping!
http://www.oreillyauto.com/site/c/se...eyword=50-3715