i have already swapped my rear disc 3.42 out of my 1989 gta into my 1989 iroc, and the 3.08 drum setup into my gta. i did this because im selling the gta. but anyways, i thought that since i am switching everything directly over, that i already have every part i needed, but the proportioning valve threads are different, the threads on the gta are fine thread, and on the iroc, corse thread, so niether will swap over to the other, what proportioning valve should i get for both cars, im trying to stay away from the adjustable one. and im not sure if i can do this but could i take the lines that go from the prop valve down to the brakes, and swap them between cars?

Sounds like your IROC has the '88 and earlier design prop. valve and lines. You have two options:

1) Buy the correct prop. valve for each car - probably around $100 or so to replace both.

2) Completely switch lines between cars.

Option 2 is cheaper since you already have all the parts, but it will be more time involved. It's all a matter of choice.

ok, that makes sense, but i think i have another prop valve off another iroc that i could put on mine iroc that will fit, but then i still have to do the gta, would it be ok to leave the disc brake proportioning valve on the gta with the drum brakes, or would i mess something up.

It's probably a better idea to switch to the correct prop. valve for the rear drums to make sure they work correctly.

Yea I switched some brake lines when I did my swap from a 89 formula with disc. It was a real PITA because I had to get the brake line that goes to the passenger front swapped out. And it went under the oil pan of the engine, which was a blast to swap out! It can be a bit frustrating at times swapping the lines out, but don't get discouraged its worth it.

-Tony

ok, after about an hour of trying to just off get the line from the passenger front wheel to the prop valve, i called it a day, i had to jack up the engine, remove the Y- pipe, and still having trouble getting it off, too much work to swap out a simple brake line, i figured it would be easier to just get some adapters to go directly to the prop valve and the lines, i would only need two for each car (female in corse thread, male out fine thread), the other three will match up. i dont know if i rememer correctly but i read some where that it is an NPT fitting, does anyone know what thread pitch it is or is it just corse and fine, and there is no pitch to it? looks to be about a 3/8" just to make it easier on the parts counter guy while hes helping, some of those guys are just too dumb to work at a parts store.

The brake lines use metric threads. This should help:

1LE Combo Valve (proportioning valve)

14089496 1989 1st design: M1.0 tube nut threads (For 1982 - early 1989 applications)
10136840 1989 2nd design:_M1.5 tube nut threads (Late 1989)
10136840 1990-'92: M1.5 tube nut threads.

another one of the great things that im going to add to my collection of stupid things the parts store guy has told me
"all the break lines have the same size fittings"
when im standing in front of him with at least two different sizes, but im going to some brake parts warehouse tomorrow, that says they have the fittings, because no one else has them.

This is just a thought, but a small hardware store that employess knowledgable people might be a good place to try.


I've been corrected below. This was a bad thought.

i tried lowes, and home depot, and a few mom and pop hardware stores, and they all tell me i have to go to an auto parts store.... but here is an update, i have switched the brake lines out of the gta into the iroc, and the iroc is running good, and hauls ***, havent had the time to put the lines in the gta yet though

autozone does have what you need. they call it european bubble flare fittings. i believe theyre green. they should be able to help you then, but theyre still autozone, dont expect miracle service

yea i know about that miracle service.... they told me "all the brake line fittings are right there" i looked for a bit, and would have ended up buying like 50 dollars worth of stuff just to make it work, but whatever, thats autozone for you, and i got everything worked out for both cars, just gotta get on it, but the gta is just gonna sit there, so im not in a big hurry for it, as long as i got my iroc

Lowes and Home Depot kinda stink for nuts and bolts ...etc. The best store I have found is OSH. Good selection of SAE, metric, stainless steel, zinc plated, grade 8, fittings ...and so on.

I doubt they would have the correct fittings for our brake lines, but for most other items they do a good job. For really special stuff I use McMaster-Carr. http://www.mcmaster.com/

They have just about anything and delivery (at least in So Cal) is usually next day.

the fittings at home improvement stores arent going to fit because they need to have the coned end on them to meet up to the surface, or it would leak under pressure.