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Proportioning Valve - Can't locate a new one

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Hoping to get a little insight on a brake problem.  I'm in need of a brake proportioning valve but, it's turning out to be a tad difficult finding the correct one.  My 69 C10 is stock, no ones has messed with the brakes but for some reason I can't find the correct proportioning valve.  I've purchased two from Classic Industries and both of them turned out to be the wrong one.  They sent 5 port proportioning valves both times but   I only have a 4 port... 2 inlet, 2 outlet factory 4 wheel drum.  Is this such a difficult problem? Seems odd.  Any advice would be greatly appreciated.

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Hey Mark, I believe that valve is more like a switch that operates the brake warning light on the dash, if you have failure in either the front or rear braking hydraulic systems. Even though everybody calls it a proportioning valve, I don't believe that valve on your particular truck does much "proportioning ". When you bleed the brakes after a repair or if you have a failure, the brake warning light will come on. The hard part is making it go out. There is a piston inside that valve that has to be centered to make the light go out. That is done by re-bleeding your brakes with the key on and observing if and when the light goes out. Theoretically if the rear caused the light to come on then you bleed the front and watch for the light to go off and shut the bleed screw off immediately. If the light goes off and then comes back on before you shut off the bleed screw then you go to the back and try it again. Sometimes it takes a number of tries to make the light go off. And if none of that works then you are back where you started from and looking for a new valve.

Also if you are looking for a new valve because your warning light is on, be sure to check the parking brake switch as both use the same light.

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Back in the day we called that valve a brake block. The master cylinder itself did the proportioning.

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Thank you so much for the responses.  That's some valuable insight.  Thank you again.

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