Proportioning valve question

[daveinluray]

Originally Posted by ray_mcavoy

The OE style combination valves have 2 front outlets that are typically plumbed directly to the left & right front calipers. But the front brake line plumbing in 71 & 72 trucks includes an inline Tee fitting so only one front outlet is needed. You can safely plug the other unused front outlet with an inverted flare plug. In fact, I believe the factory installation used a plug (rather than a special single-outlet combo valve) for the 71 & 72 trucks.

thanks. I was worried I was going to have to do brake lines again. not my favorite thus far.

[Jason Banks]

What if I have a 68 that had drum brakes and I am retrofitting to disc. I have a new valve with dual front outputs, but the original lines use a T. Would I be better off running separate lines to the left and right?

[ray_mcavoy]

Originally Posted by Jason Banks

What if I have a 68 that had drum brakes and I am retrofitting to disc. I have a new valve with dual front outputs, but the original lines use a T. Would I be better off running separate lines to the left and right?

You can hook it up either way and it won't make any difference in how the brakes function. The dual front outlets of the combination valve are basically like a Tee fitting built into the valve housing. So the only difference is the location of the Tee.

[Jason Banks]

I'm in the process of installing the proportioning valve I mention above.

The proportioning valve has 3/8 ports for the front brakes.

My original front brake lines(I assume from non-power drums, but someone had a 3/4 ton booster and master installed) are 1/4 down to the T fitting on the crossmember. Then the lines are 3/16 from the T out to the brake hoses.

I am making new lines for the front.

It does not appear that I can use a 1/4 hard line into the proportioning valve because I can't use a 3/8-24 fitting with a 1/4 line.

Would it be ok to use a 3/16 line from the Proportioning valve down to the T fitting?

[hjewell2]

Originally Posted by lolife99

drum brake trucks have a distribution block.
The 71-87 disc brake trucks have a proportion valve.
Just add the brake booster to your current m/c.
Done.

bingo

[Rickysnickers]

Originally Posted by Jason Banks

I'm in the process of installing the proportioning valve I mention above.

The proportioning valve has 3/8 ports for the front brakes.

My original front brake lines(I assume from non-power drums, but someone had a 3/4 ton booster and master installed) are 1/4 down to the T fitting on the crossmember. Then the lines are 3/16 from the T out to the brake hoses.

I am making new lines for the front.

It does not appear that I can use a 1/4 hard line into the proportioning valve because I can't use a 3/8-24 fitting with a 1/4 line.

Would it be ok to use a 3/16 line from the Proportioning valve down to the T fitting?

Yes, you should be fine.

[Jason Banks]

Thanks Randy. I was looking around and it appears the 71-72 have 3/16 brake lines from the proportioning valve down to a Tee and then 3/16 lines to each caliper. Can any one confirm the front brake lines are smaller than the others?