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R there 2 proportioning, distribution valves

883 Views 6 Replies 4 Participants Last post by  duffner
For a 70BB I have the valve on the rear frame but isn't there another valve thingamabob under the Master Cylinder? Yes, I took it apart years ago and don't have it anymore; just have my new MC and Booster. Thanks....
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Go to the web site(or google master power brakes). The tech reference section explains a metering valve (which you have) a proportioning valve, and a residual valve. Basically, all 3 functions were incorporated into a "combination valve" around 1973. Most people loosely and incorrectly refer to these combination valves as a proportioning valves. Great web site and products. They set me straight on this stuff by reading.
Most people dump the metering valve and install a newer combination valve to do all functions.
If you read your service manual carefully I think it will say the original master cylinders had residual valves built into them to hold some pressure against rear shoes. These built in residual valves were abandoned by GM when they introduced the combi valves. Know what year master cylinder you have to understand this issue also.
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