jeremyb1988

Hello everyone...I found an 87 IROC-Z a few months ago. Picked it up at Gateway Classic cars...seemed like just a run of the mill 5 speed manual IROC-Z. Well...I started to do some digging...I went to IROC-Z.com and found all these RPO codes and what not...then started doing some research.

Well I read from IROC-Z.com that in 1987 the 305 TPI was offered as a 190 HP car AUTO or MANUAL...however you could get the HARDTOP, 305 with 5 speed and the G92 code and it was rated at 215. The bigger camshaft. Also the tachs for the 350 and 305 were different yellow line markers. The 305 started at 4500 and the 350 at 5000. Well I also read the other codes that verify if its an IROC-Z, etc etc. Okay...well this is what I found to my shock. I found that my code inside my center arm rest console had the G92 rear axle code! It also had all the Level 3 IROC-Z performance codes. Every code matched how they should with the cars features. It also has a 5000 tach...which makes me think bc of the raised HP it would have a different tach? It also has the Conversion code as well! I assume meaning from the hardtop to T-tops...anyways, I'm just trying to get some experts on here that know more about this. If I had the normal 305 5 speed manual my rear axle should be the G80 code...but from what I gather the G92 code rear axle was ONLY offered with the bigger camshaft and increased HP. The only thing short of what I have done is check the actual #s on the parts themselves. The car has 70K original miles on it...while I imagine it can be a fake...and these #s could be off I find it highly doubtful that someone found a center console arm rest with the codes inside to match this and put it into there car. The VINS do match up as well the way they should, they also match on the hood as well with the top right vin sticker...thanks for the help in advanced! Just seeing if anyone has heard of this...and or there thoughts on the tach situation.

Drew

iTrader: (58)

Nothing against other websites, but you can get a ton of info right here on thirdgen.org. https://www.thirdgen.org/1987-chevy-camaro/ There's a year by year breakdown of nearly everything you could ever want to know. Granted it makes the most sense when you start at 1982 and work forward one year at a time, because the document assumes you've read the previous pages and builds on what has already been covered... Anyway, skip to the bottom of the page and you'll see a "Drivetrain chart" showing what was available on each car.

Now... G92 means "Performance axle ratio". That's all it means. If a thirdgen had a 2.73 or 3.08 gear available and an optional 3.23, 3.42, 3.73 gear available, G92 means it has the more performance oriented gear set. G80 is limited slip, and there will also be a GXX code for the gear ratio, like GU5.

Anyway, back to the drivetrain chart... We go down to IrocZ, and M5 for the 5spd.. LB9 because it's a TPI 305... And we go over to the gear ratios... Manual transmission standard gear ratio is 3.08, the Manual optional G92 ratio is 3.45. So with the G92 code you have 3.45 gears.

Now as far as a HP rating difference with G92, or a conflict between G92 and T-tops, I don't know. However I can tell you in 1987 GM didn't give much of a rip about power and ttops since they made a grip of 350 TPI ttop cars in 1987.

I'm not seeing anything really out of the ordinary.

StevenB L98/LS1

The G92 cars 87 and up with 305s get the same tachs as the 350s did, because GM put the L98 cam for the HP increase. With the injectors being different and the cylinder heads on the 305 It was only a 10 hp decrease from the 350 setup.

87 is the only year I've seen or heard of that could get ttops with the 305 G92 code. 88-92 cars I've only seen g92 305 t5 were hardtop.

jeremyb1988

Really cool information! See I had read somewhere that ALL the 305 87 manuals got the higher tach rating, this is wrong I assume from what you say? To me your argument makes more sense...bigger cam..higher HP...higher tach right? I emailed the guy from IROC-Z.com...I think maybe his information is not exactly correct...I really appreciate you input though! I really lean on this site for accurate information and no offense...but the older guys know a lot more than me. Its amazing how much people know, and I seem to find zero documentation of some of this stuff anywhere!

jeremyb1988

Hey Drew, long time no hear! Thanks for the thoughtful input man! Really appreciate it! Yes...I know thridgen has great info! Maybe I need to learn how to search the website better! I guess I feel I have a somewhat rare car and was trying to get verification on it. Maybe the G92 and the 215 HP rating on a 305 back then was nothing to brag about...idk...I feel like the guy I bought it from months ago had no idea. Drew you know all the work that I'v put into this car via our messages lol

jeremyb1988

From what I read on ur link, its really not rare at all. I was under the impression that only the hardtops had the G92 code, etc...but this link makes it sound like ALL 5 Speeds had the code...hmmmm interesting. I guess that makes sense...not that its accurate but Wiki said the same thing...if you had a manual you had the 215 HP rating...which to me is good. Between loosing the cats, upgrade exhaust, K&N air filters, airfoil deflector on the intake, I image I have about the same HP as the 5.7 motors ...all while keeping it seemingly stock. I mean that was the whole point back then on getting the bigger motor right...to go faster than the guy who had the 305 haha.

Drew

iTrader: (58)

Kind of depends on your perspective... All 305 TPI 5spds were 215hp, but not all of them had the 9-bolt rear with 3.45 gears.

Now I don't speak for anyone else, but in my opinion thirdgens with lousy gearing are generally the "Huh... I thought it'd be faster" variety, and those with the 3.23, 3.27, 3.42, 3.45, etc gears, are the faster cars (-6cylinders not included).

G92 is a good thing.

chazman

iTrader: (4)

'89 and up required a hardtop to get the G92.

jeremyb1988

Mine also has the KC4 code and the rear disk brakes...Im assuming this was automatic with the G92 option?

Can we play "what if for a moment? Let's say u had an 87 iroc with 30K good condition 305 5 speed t-tops, and the same exact one beside it with same millage and condition but had the G92 package with the disk brakes and engine oil cooler etc. The normal 305 was asking 10K, what would the more high performance one fetch for? All this is an example and you alla personal opinion of course. Not like I would sell it ever, but curious the current market I guess

jeremyb1988

Also didn't 89 and 90 year if u got the G92 it was basically an LT1 car? Meaning radio felt, no A.C. aluminum driveshaft , better fuel tank pick ups etc STANDARD with that package???

chazman

iTrader: (4)

Sounds like you are thinking of a 1LE which started in '88

In '89 a G92 got you and/or required 3.45 gears on LB9 or 3.27 on L98, oil cooler, 4 wheel discs and N10 dual cats.

jeremyb1988

I see, yeah mine has the dual cats, oil cooler etc...but I assume u could not get the radio delete etc on the 87 models, like u said 88 and up the 1LE models???

chazman

iTrader: (4)

Dual cats started in about January of 1989. If you have them, they didn't come from the factory.

jeremyb1988

Yeah NO ur right they were added...well I don't have cats at all (thank god), but its dual exhaust. Thankfully I have a buddy who owns 2 IROCS here in NC and says he knows a place that will pass me. Damn NC and there stupid emission laws lol

chazman

iTrader: (4)

So....post some pics!

jeremyb1988

Teach my dumb ads how to post pics ha. Do I have to have a photo bucket or something? I don't think they let u post pics directly from ur phone onto here do they?

Ty92Z

iTrader: (11)

NC only requires a safety inspection for anything below 96. As far as emissions it's only a visual thing. That being said, I've lived here all my life and have never had an inspector "look" for any of the emissions equipment. I don't go to any of the big chains though, just the little mom and pop on the corner. Yes, you can post directly from your phone, it's the yellow square with the mountain and sun scene.

jeremyb1988

I assume u live in NC then?

jeremyb1988

jeremyb1988

It's getting detailed by one of the best around next week and will look much better . Hey man if ur from NC we need to get together. My gf at her work seen a 88 iroc vert and took a pic and showed it to me. I told her to leave an email not I wrote to her to give to him and leave on the windshield. Anyways he hit me up, dude has owned like 15 I rocs lol
Currently has 2! He's got 2 garages and we just hang out now and work on our cars, listen to music and drink some beer lol. If u live in the raleigh durham area u should swing by or us to u! Have a little convoy of I rocs! We're all going to VIRs big race at the end of August, if u DO live in NC u should come!

Ty92Z

iTrader: (11)

Nice IROC! Yes, I'm in the Fayetteville area. Both my cars are currently getting motor upgrades, but I hope to get one back in the road in the next couple months. You're about an hour away, so could take a cruise.

jeremyb1988

Sent u a PM on here