hello after weeks of research and countless other outlets to obtain a discontinued part, ive ended up here. im looking for help with a 1984 z28 brake proportioning valve. i havent been able to find the part i need anywhere. my question is this... what is the difference in prop valves for 4 disc vs. prop valves for rear drums. i happen to have rear drums on my car. ive found tons of 4 wheel disc prop valves but none for the rear drums i need. the gm part number im looking for is 25517738 i know they only used this prop valve on camaros 84-85. please if you have any suggestions . im at a loss. i just need to know where to go from here or what other options i have.

 

Welcome to TGO, stepslow.

The old cast iron valve was found on 82-84 (and perhaps a few later cars). The threads are SAE and the lines attach differently than the later valves which were alum with metric threads. The bias is different between the disc and drum valves. As far as I know, there's no visual way to tell the difference between the two. You might advertise on our site's classifieds for an OE drum valve which would be far easier to find than the disc, I'd think. Another option would be to install an adjustable valve which is available from Summit, Jeg's, and so on.

Best of luck on your project,

JamesC

 

any tips on integrating an after market prop valve? am i going to need to replace all my old lines going to the rear as well? with the stock fittings fit into the after market prop? this silly little part is slowly becoming my biggest headache