OK, it's coming down to it. Just waiting on the hard lines from Classic Tube and the relocater brackets from Steve Spohn to arrive and I'll be ready to swap the old 10 bolt with drums for the 9 bolt with PBR discs. My question is just how much of a mess will I be looking at when I swap out the proportioning valve? Will it be a little with minimal fuss or will it be necessay to bleed the master cylinder afterwards due to the fluid coming out like a flood. Let me know any tips or tricks you may have used to help minimize the hassle too. Thanks.

There will be some leaking, but should not be a torrent.
Protect your paint- the brake fluid will take it off like paint remover.
I am hoping Classic Tube get the correct ends on the lines where ther go into the prop. valve. They caused me a lot of delay on my project by not putting the correct fittings on-even after they were specified.

The entire system will need to be bled for proper operation.
As far as the master cylinder- I plugged the outlets with rolled up paper towels and did not need to bench bleed it.

Best of luck

S-D

I only got the hard lines for the axle,not the ones that go into the prop valve. They're still OE. I'm aware that the whole system will need to be bled, my main concern was with the prop valve and hoping I wouldn't have to do too much with the M/C. Maybe I can find some of those plugs for the lines to prevent fluid loss......

Oh- I thought you had asked about bleeding the master cylinder.
I do not recall having to bleed the prop valve.
One thing to be aware of though, is that some prop. valves have different female thread/pitch on them. That is where I got hung up with Classic Tube.

I have a 91 RS with drums. I put Baer discs on the back and found a prop valve for a 91 Z-28 w/ four wheel disc. The thread/pitch for those two prop valves was different. Then Classic told me they didn't have the fittings and it turned into a real hairball.

I'm hoping yours just bolt right in with no trouble.

I know that on my rear axle, I used hardline, then ss braid flex hose to the caliper. Is yours hardline right to the caliper?

Yes the plastic cap inserts would probably work well.

S-D

So the threads are different between the disc/drum and the 4 wheel disc valves? I have the PBR brakes out back with hard lines on the axle and flex lines from the axle to the caliper. Let me know what you did to solve the problem as I'd hate to get the car torn down and get stuck for parts. Even if I have to get extra and not use them it would be better that getting stuck.

I just remembered,there were three different 4 wheel disc valves available. Which one did you use? I have one new from GM for 90-92 cars with 4 wheel disc. 10164112 is the part number I think.

The thread pitch is different on some-
here is a thread I started that has some part numbers.

https://www.thirdgen.org/techbb2/sho...ighlight=valve

I don't have time to wade through the posts right now, but a search for "drum AND disc AND valve" will likely get you the infor you need. You may want to include "pitch" in the search to help narrow it down.
S-D

you wont need to bleed the master cylinder unless it goes dry, as in air goes in through the reservoir because too much fluid leaked out.....as long as you keep enough fluid in the reservoir you wont have to bleed it.