I have searched around this brake board about Master Cylinder. It looks very confusing and I cannot find the answer to what I am looking forward. I hope someone on here who know how to answer this for me.

First, I have a 1988 Iroc that came with the rear stock drum 10 bolt axle. I swapped the rear to a 9 bolt disc with iron caliper non 1LE and upgraded the front C6 Z06 Brakes. I might change the rear to a bigger brakes later on in the future to maybe the C6 Z06 brakes.

My question, is do I need to change the stock Master Cylinder?

I could be wrong, it looks like the 1988 Master Cylinder part number 18030556 is a good choice because it has a bigger bore diameter size with front 1.42" (36mm) and rear 1" (25.4mm). I viewed from this website about master cylinder bore diameter size.
http://www.lukeskaff.com/car/brakes/...Clyinder_Specs

I don't see a specification for a 1992 "1LE" master cylinder diameter bore size. Does anyone know on this?

From viewed the website it looks like the 95-96 B-Body has a bigger bore size diameter master cylinder with front 1.575" (40mm) and rear ~1.126" (28.6mm) part number 18030951. Is that a good one?

What about the Wilwood master cylinder #260-8556 http://www.wilwood.com/MasterCylinde...inderList.aspx
bore diameter size 1-1/8". Are the Wilwood better than our stock fbody master cylinder? The Wilwood size bore 1-1/8" looks smaller than the 1988 bore size.

I do not know what the different is between the Step and single bore style. Anyone can explain this to me?


Sorry for the long information written. Hope someone here can help me out thanks.

 

No.

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

You do need to swap to a disc combination valve.

JamesC

 

Thanks James,

So it looks like I have the J50 which is a good one to use?

Where, what kind and year combination valve should I look at or find one? What is the different between the stock proportioning valve and the disc combination valve?

 

I used the J50 on my 1LE swap, front and rear, along with the appropriate 1LE combination valve.

You'll find brake info that will be helpful toward the end of the following link:

https://www.thirdgen.org/forums/tran...-10-bolts.html

The bias is apparently different from valve to valve: disc/drum, disc/disc non 1LE, and disc/disc 1LE.

JamesC

 

Thanks James,

Just to be clear. I should get the "1LE" aluminum combination valve from 1989 to 1992 disc/disc correct?

Does the 1988 have the same threat fitting as the 1989 to 1992?

Is hard to tell by looking at the aluminum valve since it looks the same what I have on my 1988 that it use on the 1989-1992.

How is the aluminum valve that GM made inside so different such as disc/drum, disc/disc non 1LE and disc/disc 1LE?

Would the Wilwood proportioning #260-11179 valve be better and work for my setup?

Let me know thanks.

 

The threads on your 88 will work fine with the first design valve seen in the following link:

http://www.flynbye.com/catalog/i40.html

There's no distinguishing what valve your car has by looking. If it's alum, they all 'look' the same.

Each braking system has a different bias.

Some members use an adjustable after market valve to fine tune.

 

That 1LE valve should polt up and your brake lines should thread right into it. It would be the easiest solution. I went after market and got a willwood prop valve but it was definately not bolt in.

 

Thanks, I was wondering about the wilwood, but since I am not sure if I want to do that or not.

I have a friend who has a 1989 GTA with disc to disc and could I just take the proportioning valve off that 1989 Firebird GTA and install it on my 1988? Just wanted to be sure since the link you showed me is the combination valve and the 1989 is the used one. Should it be the same?

 

If the combination valve is the early 89 design (1st design with M1.0 tube nut threads), yes, the threads will be compatible. If the valve is the late 89 design (2nd design with M1.5 tube nut threas), no, the threads won't be compatible.

JamesC

 

Ahh okay, that interesting.

How would I find out which one it has the first or 2nd design thread? The car he has is a 1989 GTA with rear PBR disc, 9 bolt axle, auto and 5.7 TPI. Not sure, if that would help?

What model in 1989 had the first and second design threads?

Any suggestion?
Thanks.

 

Second question first. As far as I know, first and second have to do with early and late in the production run.

Measure and/or examine the threads. If the threads look like the ones on your 88, the valve is early and will fit. If the threads appear more coarse, the valve is late and won't.

JamesC

 

I have a question regarding the P/V.

Is there a diff between those two part numbers
89 J65, 1LE(1st Design)...14089496 and
86-88 J65.................14089497

Which one should I go for and which one is better? Both are first design.

Let me know thanks.

 

Yes, there is a difference. The first is for the so-called 1LE set-up (11.7" rotors and PBR calipers). The second is for standard disc brakes (10.5" rotors and Delco-Moraine iron calipers).

If you're upgrading, the 1LE valve or an after market adjustable would be the way to go.

JamesC

 

Thanks for the information James.

I have another question. I just came across about the parking cabel e-brake. Do I need to swap out my stock e-brake cable that came with the 10 bolt axle and drum. I have the rear 9 bolt iron Caliper disc. So I am not sure I can stay with my stock drum e-brake cable? I hope I can.

Let me know thanks.

 

Can't.

JamesC

 

Oh great.

So what kind of e-brake cable I should look for and part number?

Are the e-brake cable the same use with Iron caliper and PBR disc?

 

Order for, say, an 87 or 88 rear disc car and you should be good to go.

Cables are different between Delco-Moraine (iron) and PBR (alum).

JamesC

 

Thanks James,

I did a search where to look for parking brake cables.

I have a question, do I need to swap out all of my stock drum e-brake cables? Or just the rear e-brake cables?

I search for e-brake cable and found this site: https://www.thirdgen.org/forums/brak...equalizer.html

The rear left cable I would need is part #93084
The rear right cable...not sure of the part number.
Front cable part #93132. Not sure if i need this or not. I hope not.

All of these are from Napaonline.com

Let me know thanks,
Scott

 

Just the two rears.

JamesC

 

Great thanks.

 

I have another question. I found a Prop valve from a 1989 TTA GTA with the first design M1.0 thread and I believe the part number is 89 J65 EXC 20TH Ann Y82,1LE 1ST Des..14089497. Will that work for my 1988 disc to disc.

What about this part number 14089496? Is there a different between those two part numbers 14089497 and 14089496? Which one works best?

 

I looked up the valve for J65 brakes, 1986-88 and 89 (Exc 1LE ) and the p/n number is 14089497. The 14089496 will fit your car.

EDIT: Notice that your description says, "J65 EXC[ept] 20th Ann Y82, 1LE.

JamesC

 

Thanks James, the guy told me is was the M1.0 thread from the TTA and which I looked up and found that number 14089497 that seem to be the TTA first design.

But are other prop valves #'s have diff pressure lbs or something?

 

There are three valves, each with a different bias:

disc/drum
disc/disc (non-1LE)
disc/disc (1LE)

Good luck with your project.

JamesC

 

That seems about right, but the difference isn't so much 1LE vs non-1LE. It's PBR (aluminum) rear calipers vs Delco (iron) rear calipers. The front brakes don't matter as far as the valve is concerned. The late 4 wheel disc, non-1LE cars use the same prop valve as the late 4 wheel disc 1LE cars.

 

FWIW; after doing the LS1 master cylinder swap, I'd recommend against it - The braking of it is reduced compared to my 3rdgen one. As for the prop valve - After seeing a "T" for the fronts and an adjustable prop valve for the rear, that's the ONLY way I'd go.

 

The 1LE has the alum PBR set-up; the non-1LE has the Delco-Moraine iron set-up (so it would seem to be 1LE vs non-1LE).

About the valve itself, the following, as an example from my Parts & Illustration Cat, shows different part numbers for 1LE and non-1LE cars:

Valve, Brk comb (1989 1st Des) (J65, 1LE) GM 14089496
Valve, Brk comb (1990) (J65) (Exc 1LE) GM 14089497--which seems to be the valve used in earlier non-1LE J65 cars as I mention in post #22.

JamesC

 

Thanks guys,

I just brought the 1989 TTA GTA prop valve which is the first design M1.0 thread. The car had disc to disc. So I hope I brought the correct one.

Valve, Brk comb (1990) (J65) (Exc 1LE) GM 14089497--which seems to be the valve used in earlier non-1LE J65 cars as I mention in post #22.

Do you mean the 1989 not 1990? I found the Prop valve information from this site and see post #92.
https://www.thirdgen.org/forums/brak...ing-1le-2.html

 

I was wondering if any one know what is the bias stock spring prop valve for the 1989 TTA M1.0 pressure (lbs/inch) rate is?

Also where can I find information for the prop valve pressure rate bias on other model vehicles spec?

Let me know thanks.

 

No one, knows?

I think I found the 1989 TTA bias stock string prop valve is a 32 lbs/inch. Is this correct?

 

Anyone, have any information on ( )lbs/inch prop vave rate?

 

I have a question about the rear 1988 9 bolt iron disc brakes cables.

I need the rear left and right cables. What I have found from Napa part store.

Do I need the left rear cable part #93084 which is 48.25" long and the rear right cable part #93482 which is 65.31" long?

The guy at the Auto store said they did not have the #93084, but had the #93222 which is 63.5" long.

Can anyone confirm on this which part numbers do I need?

Thanks.

 

No, one knows the part numbers or length for the 9 bolt axle iron brake cables?

Anyone?

 

I installed a 95 z28 posi disc rear into my 89 firebird and I went to install a prop valve from a 1990 formula that also had disc brakes but after reading this I guess my car was made in early 89 as the threads don't match up, so my question is will a prop valve from a 4th gen have the same threads?