No,,I've been building hot rods for many years and I do know how to install disc brakes,, I took the proportion valve off and dissembled it,,everything inside was stuck and gummed up. I decided to order a new one,,I'll let you guys know how it turns out as soon as I get it in and try to bleed the brakes again. HRP
For what its worth, I never use prop valves on hot rods or race cars. I think you said you have disc/drums. Make darn sure you have the correct master for this set up, determine if the master has residual pressure valves built in, and that they are correct for disc/drum. Ive almost always put a proportioning adjustable valve in the rear circuit, but after doing a bunch of these, 90% of the time it stays wide open. Therefore, its not needed. Looks like you solved the bleeding problem with the bad prop valve, but if it still doesnt work the way you want, eliminate it and try that. Hope you get it driving soon, want to see it in person this summer, oh ya, and say hi to you.
JFYI, when an adjustable prop valve is "wide open", it's still going to limit rear pressure. The adjustment usually ranges from a minimum of about 100 psi to a max of 1000 psi. Once the knee or crack point is reached, a percentage of master or full pressure is then applied to the rears, including when the setting is full open. The only way to know for sure if you don't need a prop valve is to remove it, but considering most/all US production disc/drum vehicles use one, the odds are you will also. Internal residual valves became obsolete in the mid '70s, so you have to check every master you use for their presence, even if the original application had them.
Just for clarification,,I purchased a new master cylinder for a '84 Mustang and used the '84 Mustang proportion valve ,,I guess sitting in a box for several years helped dry the proportion valve out. HRP
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