Austin19

Hey folks,

I have a '85 Camaro IROC-Z with the 4bbl LG4. I want to do some modifications to it since I have some money laying around. I see pretty often about people changing their rear end gears to something different here on TGO. My first impression was that a 3.73 would be good for me (because in my head, the bigger the number, the better it is). I did some research, and obviously, thats not quite right.

So what do you guys recommend for a (so far) unmodified automatic LG4? Right now I have the 3.23, and, as I said above, I was initially thinking of going to a 3.73. As of now I am not going to go to a track, but I think I will end up going to do a quarter mile a few times once I do most of my modifications. From what I've read, the 3.23 seems to be pretty well fit, but I was just wondering if anyone has any advice they'd like to give me!

Also, if anyone knows of a good, informative site where I could figure this out for my own, I would be happy to take a look.

KrisW

iTrader: (5)

This is a GREAT site to figure out the answers to your questions. Search more and you can spend days reading the results...

Me personally, the 3.50-ish gear ratio is the best all around daily driver gear. The 3.73 or 3.90-ish if you have the T56.

That's just me personally, and everyone is different. That's why you need to do some hard core searching.

sofakingdom

iTrader: (1)

Yeah the 3.23 isn't too bad. NOw if you had a later car with the 2.73, that would be a different matter.

3.73 will make the car launch like a bat outta hell, but peter out at about 5 mph. My little bro did exactly that swap to his otherwise totally stock LG4 Z28.... I could line up at a traffic light behind him in my L69 car, and pull around his and pass it about halfway through 2nd gear in my car (5-speed... his was an auto). Driving his, it felt GREAT when you stepped on the gas, but it was basically impossible to pass a semi on the highway at 55 mph, because the engine simply had no power at that speed. That's what too much gear does, and what your car will be like with 3.73s.

I'd suggest for your situation, start with exhaust; every piece from the heads all the way to the street; chassis-specific to the 3rd gen (NOT "universal" ANYTHING), BUT NOT for the LG4. Instead, get the headers, cat, & cat-back for something like a 88 TPI 350.

You are already at the good, informative site.

Austin19

Thanks for your opinion!

What do you mean exactly when you say I should get the exhaust for a 350 TPI? Just bigger, can handle more power? I have already been looking into exhaust, and I am leaning towards this setup: Hedman 68470 Headers with matching y-pipe 17478 (would get it ceramic coated here in Calgary), Magnaflow 94026 cat, Hooker 16820HKR cat-back. This system would bring the tubing down to 2.5" at the cat...is that exactly what you meant when you said I should get a system for the 88 350 TPI instead of the LG4? A 3" setup?

HUSSAIN

good luck

KrisW

iTrader: (5)

I think sofa is trying to say that the cat-back systems and converters are listed very often by what type of engine and what year the car is, and that you should specify that you want parts for the VIN code "8" 350 cars. The converter and cat-back should be 3 inch for those if you are buying performance parts.

Your exhaust manifolds and y-pipe suck. Even if you were on a shoe string budget, just changing out to TPI manifolds and y-pipe gives you a drivable difference. When ordering headers, don't forget that you need a new y-pipe as well!

I keep hearing Hooker 2055 or 2076 for headers, but I don't run small block chevy anymore in performance applications, so you should go to the exhaust section and start searching around. Generally, those headers (1 5/8" primary if you can) and a good y-pipe added to a 3" high flow cat and 3" cat back will be a good start.

I just gave my mom my 89 bird (305 TBI) and the first mod that it is getting is a set of factory 89 IROC manifolds and y-pipe, along with the cat back and cat mentioned above. That is just for normal driving, but I want the advantages that I can get from a budget!

Austin19

Thanks for your help, Kris! Lots of great info! I will definitely be getting a 3" system after hearing that!

jmd

iTrader: (4)

Sounds like an early LG4 w/ small valves and too-tight secondaries to me; never had a problem passing semi's w/ the LG4 cars I've driven but they're no cammed L69.


I've done cams, exhaust and intake manifolds on a few L69s and LG4s.

If you're not going to cam the LG4, keep the 3.23 gears.

In order, you should do headers and you might prefer to go dual-cat routing of the exhaust (which was used '88-'92; I don't know emission laws for AB.) The exhaust manifolds are the single biggest choke on the engine.

Then consider doing a mild cam and maybe intake manifold.

The 3.73 gears tend to work excellent for a cammed engine that's making power above 5000rpm.

All this might be disappointing if the '85 LG4 heads are kept; I believe those are the ones with smaller valves while later ones had the same size as the L69. So you fall back to "might as well do a 350 or bigger" argument.

Austin19

I am planning on camming it at some point, however I think that will be a bit later in the project (after exhaust, air intake). You're saying that the headers should be done first in the exhaust system?

For the dual-cat, does that just use an x/h-pipe and go dual to exit? There are ABSOLUTELY NO emissions laws in Alberta oddly enough, the only law about exhaust is that it cannot shoot flames or sparks...

And thanks to everyone's help here, I have decided that the rear end will definitely be something I do closer to the end of my modifications.

jmd

iTrader: (4)

Yep; headers first for sure.

The dual-cat routing on the OEM setups was pretty snake-like all through the passenger side. Look through some other threads on what people are doing; I know there are some people doing duals down both sides of the vehicle or keeping the passenger side. That has an impact on which headers you use so get a game-plan going.

Austin19

I already sort of have a game-plan, but I will look into the dual-cat routing. FYI, my current plan is to have Hooker 2055 headers, a high-flow Magnaflow cat, and the Hooker 16820HKR cat-back. To me, it seems like a very good setup for ~$1100