There seems to be a lot of contradicting information or people don't go into a lot of detail. Which proportion valve will work as a direct replacement in my 84 Z28 that's going from drum to LS1 rear? I've looked on summit and Googled it but I don't want to buy the wrong thing. Thanks in advance.

Here is a pic

 

i took the spring out of mine to make it into a distribution block and put a Wilwood adjustable prop valve in the rear line after it.. required some flaring to replace some metric fittings with sae, but not difficult at all and it works great.

 

The combination valve above appears to be an SAE model.

James

 

well, then, that just makes it easier.. you can actually get the npt to sae flare adapter for the prop valve so no cutting and flaring and realizing that you put the fitting on the tube backwards so you have to cut it apart flip the nut and flare it again..

 

LOL, Hate when that happens. No matter how hard I tried I could not get it to thread into.......

 

Is the spring on the bottom under that nut and rubber piece? and is that spring the only thing making it a four disc prop valve?

 

Just would like to update and answer at the same time. Yes the part sticking out the bottom front holds the spring. I initially bought a prop valve from summit that was supposed to fit but it had inverted flare fittings and mine were bubble flares. So I tried the 1NCR5 (I think that's right) spring and it works like a charm.

 

1LE

http://www.flynbye.com/catalog/i160.html

 

That looks just like the P-Valve I just pulled off of my car.

I have a couple of threads here where I was trying to identify what the PValve was doing and finally getting rid of it.

https://www.thirdgen.org/forums/brak...questions.html

and

https://www.thirdgen.org/forums/brak...up-thread.html

I recall hearing that the drum P-Valve was better for LT1/LS1 rear disks and the disk P-Valve was better for the early iron rear disk calipers (Moraine?).

I think that the only real difference is the size of the spring.

I removed by factory P-Valve in favor of an adjustable one and a line lock, but if I had kept it, I would have picked up a variety of springs and, through trial and error, decided which one worked best for me.

BTW, I did not need to cut or reflare anything to install the adjustable P-Valve.

BTW, keep in mind that P-Valves for 85-up cars are not same as for pre '85 cars (not sure if cut off is '84 or '85). The newer cars have the aluminum P-Valve that does a bunch of extra stuff and uses a different style flare on the hard lines. I don't think that a 1LE P-Valve will fit without reworking your brake lines.

 

The 1NCR5 spring I put was noticeably stiffer than than spring they used for drum. I doubt it would've done much good.

 

Are you saying that the drum valve is "better" for LS1 rear disks without modification? My car is a '92 with rear drums and I am getting ready to swap and LS1 rear end right now, the P-valve being one of my big hold ups as far as what to do with it. I've read a lot of conflicting things.

 

It is just a dim recollection of something I heard years ago, but yes.

It makes sense to me, that the smaller diameter drum cylinders would need more pressure. In any case, the main difference (as I understand it) is going to be the spring, which can be changed.

I would be inclined to try the new rear disks with the P-Valve you have. If it works OK, great! If not, you can always swap out the P-Valve spring. Just make sure you test it thoroughly. You do not want to wait until an emergency to find out that your rear brakes are locking up first.

 

I tried to get at my to do a spring swap today and couldn't break that bolt loose. Any suggestions before I break something?

 

I got my spring swapped out but my pedal is still soft as ****, feel like something is very wrong. I have tried bleeding the brakes 3 times, 3 different ways, not sure wtf is going on. Any ideas? I have an 85 car same valve as pictured above just did a 99 ls1 rear end swap.

 

I am doing a front and rear 1LE conversion on my 82 and I am using a 1989 4-wheel disc brake prop valve.


Note that the later model blocks have two valves built into them - one in the front and one in the back. The front valve appears to be the prop valve. the rear is most likely a metering valve for the front brakes.

 

Did you buy adapters, are you planning on re-flaring your lines or ...?

 

The 82 valve is SAE while the 89 will be metric (and there are early and late 89 versions with different tube nuts threads). If you haven't already seen the following link, it may prove useful:

http://web.archive.org/web/200605221.../1LEbrake.html

Here's a bit more on the rears:

https://www.thirdgen.org/forums/faq-...iscs-89-a.html

JamesC