brake question

[frankslagoon]

my 63 C10 just has on line goin to everything from one master cly. at the tee going to the rear brakes they go to a smaller dia. line. The slave clys. are all the same dia. I think just usen a dual cly. master cly. and a real adjustable proportioning valve for the rear is probably the way to go on drum/drum. I'm pretty sure if the frts fail we only lose halve of the master cly.

[davepl]

There are two functions (and more but let's keep it simple):

Distribution - one line in, two out, for example
Proportioning - adjusting pressures between two circuits in a relative manner

Combined they are (wait for it) a "combination valve". A proportioning valve, like a distribution block, can be purchased separately and is a different thing.

So, not to be "that guy", but we might as well keep out terms straight. In the vast majority of cases, people mean "combination valve".

[RodnRudy]

To answer frankslagoon's question, no you don't need a distribution block in a drum/drum system. Its only function is the warning light if front or rear fail.
The brake pedal will tell you, you'll lose some pedal pressure.

[frankslagoon]

That's what I thought. ok good

[30 a truck]

I wonder why my truck did not have a proportioning valve on it?? But with a few other things that I have saw that the PO did, it does not surprise me.

[Keith Seymore]

Originally Posted by RodnRudy

To answer frankslagoon's question, no you don't need a distribution block in a drum/drum system.

Actually - you will, because there is only one line (or two lines) out of the master cylinder but you have four wheels.

Drum/Drum - single pot master cylinder: one line out of master into distribution block, three lines out (LF wheel, RF wheel, rear system).

Drum/Drum - dual pot: front line out of master cylinder into "T" distribution (LF wheel, RF wheel); one line out of master cylinder to rear system.

So a simple "T" block at the least, even if no switch is desired.

K

[Keith Seymore]

Originally Posted by 30 a truck

I wonder why my truck did not have a proportioning valve on it?? But with a few other things that I have saw that the PO did, it does not surprise me.

Sounds like an oversight in the PO's "system design".

I would recommend that you install an adjustable prop valve in the rear system (like from Wilwood or a similar race car manufacturer).

There are three elements that can be tuned in a production prop valve: meter, split point (psi) and slope (front vs rear). You can grab any prop valve and it will flow fluid but the odds of it being optimized for your set up, right out of the box, are pretty much nil.

The adjustable valve would allow you to tune for your specific weight distribution, dynamic weight transfer and respective brake torques on the fly.

K

[30 a truck]

This is a factory disc/drum setup. Why would it only had the "block" that I showed in post #1? One line going to a tee on cross member for front & one line going to rear. No proportioning valve.

I will run a proportioning valve like is called for.

[RodnRudy]

Is it possible the PO just changed to discs up front without changing the M/C and distribution block?

[30 a truck]

Very doubtful. Truck was bought for a 15 year old, torn apart by body shop to be painted, kid lost interest, parked it outside. When I bought it, I replaced spindles, rotors, calipers, whole 9 yards. Rotors were worn badly. I am 99% sure it has been on the road this way.

[RodnRudy]

You say the rotors were worn badly, that makes me believe the M/C is drum/drum. The reason being on a drum/drum M/C there are residual check valves in the piston bores.These check valves allow some brake line pressure, about 10# to remain in the line when you release the brake pedal. That keeps the wheel cylinders from collapsing from the brake shoe return springs. The shoes stay closer to the drum so you don't have so much pedal travel. 10#'s of residual pressure on the front rotors will eat up pads and rotors in a hurry.
Hope this helps.

[30 a truck]

No way to ever know what went on before I acquired it. Main thing is get it right now.

Thanks for all the comments.

[RichardJ]

>>10#'s of residual pressure on the front rotors will eat up pads and rotors in a hurry<<

Or, the rotors could just simply be worn out.

Check to see if the MC has the residual valves by inserting a toothpick or paper clip into the hole. It will be in about 1/4" inside and sits inside the back of the brass seat.
Pull the brass out, remove the valve and spring and reinstall the brass seat. Installing the brake line will fully seat the brass.
You should only remove the one for the disc brake line if you find one.