Ok. I might be a little lazy however there is almost too much info ( and some of it conflicting!) to search for which combination valve to use for my brake upgrade.
Details are: '87 Sport Coupe currently with OE discs and drums. LS1 front calipers from a 2001 Camaro (with mods as per Lukeskaff.com and Flynebye), PBR rear calipers (Origin unknown but I can still find a listing at NAPA for an '88 with the 1LE option that matches). The rears will be fitted to a Dana 44 rear axle assembly. I have all of the components (backing plates, modified spindles, hubs, etc.) however I haven't made the decision as to which valve/master cylinder to use.
I've read where the stock disc/drum prop/combo valve can be used. I've also read the the J65 valve is required. There are also various accounts of which master cylinder to use. And still others have listed adjustable valves ( I'd prefer OEM) or gutted valves (no thanks!).
Any info is appreciated.
Thanks in advance.

 

Hey, Skinny,

I assume that the upgrade you speak of is essentially similar to the J65 1LE set-up: Alum two-piston fronts and alum single-piston rears. I installed the 1LE set-up as originally configured by Dan Burke, AndyZ28 and others, which meant the appropriate 1LE combination valve (first or second design) and a disc/drum master. The car stops darned quick with that set-up, and I have no qualms about it. At some time Aperion posted the following link, which basically says that either master, drum or disc, can be used:

https://www.thirdgen.org/forums/susp...fferences.html

Some members mention that they've continued to use a drum combo valve in their disc swap and all's fine. I'm not convinced. GM, after all, manufactured both J50 and J65 valves for a reason--and reason says that GM wouldn't manufacture two valves if one were sufficient for both applications.

JamesC

 

Thanks James,
I agree with you on all counts. The J65 valve was manufactured for a reason.
It looks like I'll have to contact Mr Miller (again) for one of his combination valves.
From what you've described the disc/drum master ( and from what I've just read in the link you posted ) the disc/drum booster will work so I should be OK in that regard.
Other details such as flex lines ( I will upgrade to braided stainless ) will have to be determined once I disaasemble the '87 and check what type of fittings I have or will need to get. I've crossed over so many model years and generations that I really don't have a clue what I've got. Then of course there's the parking brake...

 

when I swapped to rear disks, the stock drum rear proportion valve would barely actuate the rears. All front brakes.

Is there that much difference between the proportion valves for the pbr rear calipers and the non-pbr rear calipers?

 

I was trying to find the post that listed the prop valves in their order of rear bias. I believe it's disc/drum (as the rear drums require the least amount of rear pressure) folowed by disc/disc and finally disc/disc ILE. Apparently there is a difference.
I believe what Flynbye sells is the disc/disc ILE version.
I'm guessing that you have rear PBR calipers however it's worth noting that the Delco/Moraine iron calipers are notorious for not working. There was a fix issued by GM to repair a design flaw. Doesn't matter which prop valve was used in attempting a repair.

 

Hey, Brad,

PM received. There were three J65 valves: one from 82-83 or so. This one is cast iron and has SAE fittings; moreover the lines mount differently than later years; an alum one with metric fittings from 84 or so to 88. Both of these were designed for J65 brakes with 10.5" rotors and iron Delco-Moraine calipers. Another, though it looks exactly like the 84-88 version, was designed for a different brake system, which used 1LE fronts (dual piston alum calipers) and/or rears (single-piston alum calipers/PBR's). Two metric designs for this latter, a first and second. Take note that when Ed Miller sells his rear PBR kit a 1LE valve is included. I've linked you to the correct valve in another post.

JamesC