adjustable proportioning valve

[zicc1835]

I would like some recommendations on a adjustable valve anyone has used . A friend has a 71 c-10 disc drum ...was a long bed he is being told he should get an adjustable valve because its been converted to a SWB some time ago he says the rears are locking up ...its manual master no booster chamber funny as I write this my original 71 SWB manual brakes the rears Lock up if I need to panic stop
thanks
Jess

[Southcity]

If the truck had disc/drum to begin with (factory) then it should already have the proper Master Cylinder and Proportioning valve for this setup. Converting it from long to short would not make a difference other than new rear brake lines will be needed. The rear drums will almost always lock up in a panic stop on these trucks since the rear end is quite light. I would verify the current setup first before any money is spent on anything.

[tdangle]

Another thought is to duplicate the setup on newer trucks that would adjust the rear braking per the load. I had an 88 chevy 1 ton that had a setup mounted on the rear axle and tied to the body. It was some sort of valving that as the load in the bed increased it would let more fluid go to the rear drums and if empty less fluid to the rear drum brakes. Kind of like a load leveler tied to the brakes

[stomper]

I'd guess the brake master and proportioning valve are identical for long bed and short bed trucks so the idea that shortening a truck somehow requires a different proportioning valve is BS.

[HO455]

I believe the reason they are the same as they are not really proportioning valves but distribution blocks that contain the pressure differential switch. True proportioning valves didn't come along till later.
Adding a separate proportioning valve is a good addition to help make braking in today's world safer. It is one option but it does require some testing to be sure your system is working as expected. But it may be able not fix a system with mismatched components.
Transplanting a later model proportioning valve works to but you have to make sure all components are the same. Master cylinder bore diameter, caliper bore diameters, rear brake cylinder/caliper diameters, and rotor/drum sizes, need to match the donor vehicle, otherwise you may have made things worse.
Remember that a proportioning valve doesn't limit the pressure to the brake cylinder/caliper it just slows how fast it is applied. You must have the brake calipers/cylinders matched to the size master cylinder and to the size and composition of the frictions. Especially when you are at the limit of the tires ability to grip the asphalt.
There is a reason quality brake systems are not cheap.

[Sheepdip]

To answer your question Wilwood makes a very nice proportioning valve. I put this one in my 40 Ford. The plugged middle port on the left side gives you the option to feed individual lines to the front brakes. If you don't need the stop light switch (comes with the unit) coming out the top you can plug it also

Good unit works well

[LS short box]

I've used the Wilwood valve plumbed into the rear line. Once you get it plumbed and bled take it out and do some normal stops and panic stops. Adjust as needed.