Quote:
Originally Posted by kev2809
also, isnt the 71-72 the first prop valve to have disc/drum setup...since disc brakes werent availve til 71?
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Correct.
The 71-72 Prop valve is the first disc/drum prop valve.
They are also unique.
They have 1 front and 1 rear line "in" from the master cylinder,... and have 1 line "out" to the rear brakes,... BUT,... only have
1 line "out" to the 2 front wheels.
This is because the 67-70 trucks, and the 71-72 trucks,... both have a "T" fitting on the back side of the crossmember to split the front brakes to the left and right wheels.
All the 73-87 prop valve (and most aftermarket prop vales) have 2 front brake line "out" ports.
This is because the 73-87 prop vavles were frame mounted in front of the engine, and had:
* 2 individual lines "in" (1 line "in" for the front brakes, and 1 line "in" for the rear brakes).
* 2 lines "out" to each front wheel's rubber caliper brake hose.
* 1 line "out" to the rear axle where it gets split again at a "tee" in the rearend housing.
So when you try to hang the 73-87 prop valve (or aftermarket prop valve), on a bracket under the master cylinder on the stock 67-72 trucks,... you will be required to plug 1 front line "out" port.
I'm not very familiar with the earlier 60-66 trucks smaller M/C.