i swapped LS1 front brakes onto my 86 Camaro with rear drums a couple of years ago, and i love them.. i only changed the brakes: all the rest of the braking system is stock, and it works amazing with great pedal feel..

i've been looking for a disc brake LS1 rear to swap in to complete the brake package, and stumbled across a low mile 3.42 rear end with the goofy gear differential and disc brakes off a 2002 Z28 convertible that was driven by an old man until he got hit in the front by someone that blew a stop sign. it's the non traction control model, so my stock hydraulic line should hook right up.

anyways, i got the rear end, master cylinder (but not the booster), torque arm, and lower control arms from him and am trying to figure out how to swap it in and get it working without throwing a bunch of money at it... my thinking is to use the new master cylinder, gut my stock prop valve to make it into a distribution block, and put a $40 Wilwood adjustable prop valve inline after it.

one other thing while i'm asking: can i use the torque arm that the guy gave me with the rear end? it was a 6 speed car, and mine's an automatic. if it will work, i'll brace it up a little bit to make it moar stronger and put it in there, too..

 

no one has done this before?

 

Use the torque arms from your car, it will bolt right on that other 10 bolt, or get an aftermarket

 

i got the rear end in on friday: 100% easy bolt in, except my particular home brewed exhaust won't let me run the fatter aluminum driveshaft and the late model torque arm has the flanges stamped in the opposite direction where it slides into the mount on the trans, so i used my old parts for now... test drove it with the '02 master cylinder and stock prop valve: no rear brakes... so i took the spring out of the prop valve: too much rear brakes. decided to plumb the Wilwood adjustable prop valve inline: no one makes a 12mm metric flare to 1/8" NPT adapter fitting, so there was some flaring that needed to be done.. things were going well, then this happened at about 11pm:



which wasn't a killer, but when i tried to cut the end off the tube, the wheel in my $3 clearance bin special tubing cutter decided to shatter... so i came inside..

got a new tubing cutter on saturday morning and got the prop valve plumbed in and did a quick gravity bleed of the rear brakes while i put my tools away... test drive gave me a soft pedal due to air in the system and i had things to do the rest of the day so i called it quits.. on sunday it snowed, and that's where it's at right now.. i think the prop valve will make it all work well together once i get a chance to tune it.

 

Damn MN!! lol. yeah, I dont think that fitting will thread on right.... Good work man! I am eventually going/thinking of doing a brake upgrade. I have disk all around now frmo factory. Wonder how much of an improvement I will get.. I am also starting to get an itch to restore the car back to stock.. Got all the parts... As I get older I am kinda loosing interest in spinning wheels and buying new rubber..... Kinda.....

 

drove about 20 miles today: rear brakes work too well once they get pumped up, but i think there is air in the system yet.. need an assistant so i can actually bleed them..

can't wait until i can actually get these brakes dialed in..

so apparently using the 98-02 master cylinder and taking the spring out of the prop valve and running an adjustable prop valve downstream on the rear line is the way to make 4 wheel LS1 disc brakes work..

 

IIRC the (rear) drum brakes need less pressure than discs, that's why the discs did little to nothing with the drum-rated spring in the prop valve.

Increasing the spring rate, such as using the Grainger 1NCR5, increases the rear pressure and rear brake function over the stock disc-rated spring, and moreso over the drum-rated spring.

So, removing the spring would seem to DEcrease rear braking. BUT, if you also took out the plunger, you gave FULL brake pressure to the rear, which is definitely too much.

In summary... just changing the prop valve spring to a 1NCR5 (30.82 lbs/inch) is more rear braking than the stock disc prop valve (spring) provides, and has been reported to be a decent upgrade.
Note: there is an even stiffer spring, 1NCF2 with a 37 lb/inch rate, that has been reported to be too much (pressure to the rear brakes).

References:
Here and here

 

taking the spring out fills the cavity with fluid, which is an incompressible fluid, which means all the pressure coming out of the master cylinder is going to the rear brake line. just removing the spring and letting it gravity feed made the rear brakes noticeably better and the rotors noticeably hotter after only a few stops.

just gotta do an actual full on bleeding ritual on the brakes and get the new prop valve adjusted.

 

While that is certainly the best way... when in a pinch I take a cut off broom handle and wedge it between the pedal and front of the seat. Push the pedal down and put the stop in place, go open the bleeder, shut it off, repeat. It does take a lot longer and you have to get the handle length right, but it works.

 

been there, done that... this isn't my first rodeo: been working on my own junk for the 24 years that i've been driving, and on cars in general for pretty much my whole life. just never done a rear disc swap on anything before.

remember, i've got a Wilwood adjustable prop valve inline after the stock prop valve: i want full pressure past the factory one, which will be tuned with the Willwood valve.

 

Not trying to hi-jack the post, but this post seems to have the most specific info about springs given.
About what spring rate (or Grainger part) is a stock disk/drum prop valve for the rears? I've got drum rears and will be installing C4 12" Front and it sounds like the disc/disc spring combo will not be quite right. If I am understanding MoJoe correctly, I should be looking for something between the 1NCR5 (30.82 lbs/in) spring and a stock spring (whatever that is).

 

i ran my car for 2 years with the LS1 front brakes with the stock rear drums. i didn't touch the master cylinder or prop valve, and the car stopped amazing.

just gotta dial in this rear brake thing: put new NAPA ceramic oem equivalent pads in the rear today to match what's in the front, and it stops better. didn't do any really hard stops yet, tho.

 

Yeah no worries, just in case you hadn't tried that one.

I would just bypass the factory PV and use the WW valve on the rears. That way you know the factory valve isn't affecting anything. You may be able to gut the factory valve but you'd still have to make sure the f/r were separated.

 

I have disc/disc so take this with a grain of salt but if your car had disc/drum factory then after you add the C4 brakes I would start with the stocker. Drums usually don't need a lot of pressure to work. I first started by shimming my stock, then went with the "middle" spring. These cars can use more rear but you certainly don't want to lock em. When testing I did some braking during turns in the rain and with the higher spring it would tend to lock (not bad though) so I dropped back a spring. Sorry I can't remember the numbers off hand but it was the ones from grainger everyone recommends.

 

When you say "shimming my stock," what are you shimming? Inside the prop valve where the spring presses against the screw-cap?

 

Yes, shimming the stock spring. Sorry, that was not well stated. BTW which ever spring you use it is a bit tricky to keep the spring compressed while you start the threads on the cap. I think I used a socket to press against it while turning it with a wrench to "feel" the threads. It took me a couple of attempts to get the hang of it.