Q: Front Valve (Round), Rear Valve (Rectangular)
I am confused my the nomenclature for the proportioning valve. I have seen and heard it called a couple different names. Which is correct?
A: To further clarify, I looked it up. The valve on the frame rail of V8/AC cars is referred to with two different names. The parts book calls it a “rear brake pressure proportioning valve”, and the illustrations catalog calls it “rear brake pressure regulator”. When I was in automotive tech school 100 years ago, it was referred to in textbooks as the “proportioning” valve, since it alters how much portion of the braking occurs at one end of the car.
The other thing I learned is the part number is the same for 1967 through 1969 Firebird, and that’s the ONLY car it’s listed for. P.N. is 3908326.
A: SO look it up in your Funk and Wagnall( any one remember that one?) In the shop manual its described as front brake metering valve(round one) and rear brake metering valve(rectangular one).Since inconsistencies are in GM nomenclature how can we expect anyone to come up with the same name. So I say lets just call it the round valve and the rectangular valve, because they both meter and they both proportion.Its all relative to flow vs. pressure which is relative to each other anyway.
A: The rectangular valve mounted on the frame rail under the drivers seat is a rear brake metering valve and is for V-8 A/C D.B. cars only. The round cylindrical one thats just under the master cylinder is the front brake metering valve and is on all D.B. cars. Later years(71 and up) used a combo valve which had all valving and brake warning switch in one.
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Content last modified: January 23, 2014 at 9:36 pm