Brake Proportioning Valve Question

flt-blk · December 31, 2004, 01:51:20 PM

Details:
55 Studebaker
Dodge Diplomat front clip with 11" rotors, single piston calipers
88 Firebird GTA 10 bolt GM Rear 10.5" Disk Brakes, single piston Calipers
Universal 7" Booster
69 Corvette 4W Disk Power Master Cylinder
Firebird GTA Proprotioning Valve

The ProportioningValve has one outlet for the Rear and two outlets for the
front. I want to run a line lock (Makes burnouts easier).

Question: Can I plug one of the front outlets?

The Master Cylinder reservoirs appear to be the same size, One has a
small outlet, the other is larger.

Question: Which one is front? I assume the larger outlet goes to the back
like normal.

Thanks

tomslik · December 31, 2004, 02:26:33 PM

Quote from: "flt-blk"Details:
55 Studebaker
Dodge Diplomat front clip with 11" rotors, single piston calipers
88 Firebird GTA 10 bolt GM Rear 10.5" Disk Brakes, single piston Calipers
Universal 7" Booster
69 Corvette 4W Disk Power Master Cylinder
Firebird GTA Proprotioning Valve

The ProportioningValve has one outlet for the Rear and two outlets for the
front. I want to run a line lock (Makes burnouts easier).

Question: Can I plug one of the front outlets?

The Master Cylinder reservoirs appear to be the same size, One has a
small outlet, the other is larger.

Question: Which one is front? I assume the larger outlet goes to the back
like normal.

Thanks

put it in the line BEFORE the prop. valve.
(m/c side)

smaller line is USUALLY the front...

enjenjo · December 31, 2004, 04:43:21 PM

Quoteput it in the line BEFORE the prop. valve.
(m/c side)

This would cause the valve to shut off the rear brakes when you release the pedal. Next brake application, no rear brakes.

Yes you can plug one of the two front outlets. Or use an S10 valve, it has only one outlet on the front.

flt-blk · December 31, 2004, 08:04:40 PM

Doh, :oops:

I can make room between the Master and Proportioning valve on the front
line. I was stuck in the box.

enjenjo, there is a front in and a rear in. The rear has its own
independant section of the prop valve so the rear should be fine.

Thanks

enjenjo · December 31, 2004, 09:09:46 PM

Inside the proportioning valve, there is a shuttle valve. It's held in the center when the brakes are applied because there is equal pressure on both sides of the valve. If the line loc is installed between the master cylinder and the proportioning valve, when you set the line loc, and release the brake pedal, there will be no pressure on the rear, and the shuttle valve will shut off the lines to the rear brakes. Releasing the line loc will not recenter the valve. So the next time the brakes are applied, the rear brakes won't work. They may work after several brake applications, or they may not.

flt-blk · December 31, 2004, 11:04:37 PM

Uh oh,

I guess it's back to plan A and I figure out how to block off one of the
openings.

Is that what the pin under the grommet is for, to reset the slider?

enjenjo · January 01, 2005, 12:14:35 AM

Actually it's to lock the sliding valve for bleeding. Not all valves have it though. Some have a switch mounted there.

Bruce Dorsi · January 01, 2005, 12:49:33 AM

Quote from: "enjenjo"Actually it's to lock the sliding valve for bleeding. Not all valves have it though. Some have a switch mounted there.

================================
Some of the free-standing metering valves (not combo valves) have a pin to depress for bleeding.

Do these metering valves have a shuttle in them, or is the pin to manually overide the spring tension?

enjenjo · January 01, 2005, 02:01:28 AM

The ones I am familiar with have a pin on the top side that locks the valve in the center. the ones I have seen with an over ride pin have that on the end, and generally only have one line in and one out. This what you are talking about?

PeterR · January 01, 2005, 03:59:36 AM

Quote from: "enjenjo"The ones I am familiar with have a pin on the top side that locks the valve in the center.

Are you sure the pin holds the shuttle in the center? I have seen some with a pin that climbs a ramp the as the shuttle moves away from centre, then when fully to one side the pin jumps into a groove to retain the shuttle and prevent loss of fluid from the failed circuit. The pin has to be lifted to allow the shuttle to return to centre.

enjenjo · January 01, 2005, 04:32:21 AM

Well, it's obvious that there are several types of valves here.

the only ones I am familiar with are the ones with a pin that is spring loaded out, and has to be held in for bleeding. And I have only seen a few of those on 70's cars. Most of them have a switch in the same port that lights a light on the dash when one side or the other loses pressure. the ones with the switch can be reset by opening a bleeder on the side opposite the one that lost pressure, and gently pushing down the brake pedal until the light goes out. You can remove the switch, and recenter the valve with a pick if it is stuck, as long as it isn't stuck too bad.

The other type is round, with two ports, one in and one out. with a pin in one end that can be depressed for bleeding.

There may very well be one like you describe, but I haven't run across it yet.

PeterR · January 01, 2005, 08:18:32 AM

Quote from: "enjenjo"the only ones I am familiar with are the ones with a pin that is spring loaded out, and has to be held in for bleeding..

That would sure make bleeding easier. Can you hold the pin down against the spring with some insulation tape or vice grips to bleed the brakes without an assistant.

QuoteThere may very well be one like you describe, but I haven't run across it yet

So, I haven't seen yours and you haven't seen mine

enjenjo · January 01, 2005, 01:51:32 PM

QuoteSo, I haven't seen yours and you haven't seen mine

And lets just keep it that way , ok ?

The pin doesn't take much to hold down. A pair of pliers with a rubber band doubled over the handles is enough.

flt-blk · January 01, 2005, 04:03:37 PM

My valve has a sensor in the middle with a spring loaded pin
for an idiot light. I can see inside and the pin sits in a slot,
when the valve goes one way or the other it pushes the pin up
on a ramp closing the circuit.

I pulled the springs out of both ends of the valve and I can see
the slider in the middle, but I cannot get it to manually move,
how much pressure are we talking about.

To reset the slider from the front there is a pin that sits flush with
the end cap at neutral, I assume it will poke out if this side looses
pressure.

The rear has a pin hole and it looks like you have to insert something
to reset it.

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Questions;
How are these tuned? Does the spring tension determine the proportioning capability.

Is there a difference between Disk/Drum and Disk/Disk?

If I find an S-10 valve will it work as well, I am using this one because
it came off the Firebird with similar rotor size, car weight, and 4WDB.

enjenjo · January 01, 2005, 05:00:28 PM

Strickly speaking, these are not proportioning valves. What they do is hold off brake application in the rear to get it in sync with the front brakes. Basically what it does is to make the rear brakes reach a higher pressure before applying. If fine tuning is needed, I usually do it with wheel cylinder sizing.

The S10 valve has a bit more delay than most car valves, which I have found to work good on hot rods, because we tend to use much bigger tires on the rear than we do on the front. It makes for a more balanced system.