I posted this here since it was such a broad topic. If anyone knows where it more correctly belongs please say so.

I am in the USAF stationed in Germany. I recently purchased a 1988 IROC-Z. It is currently on a ship headed this way. Here are the particulars that I know about it up to this point. Also, this will be my daily driver mainly because I really like driving these cars. I do not want to go to crazy on the mods but I was considering a mild stall to help with the acceleration from a standing start. I will list options that I am considering at the end of this message.

1988 Chevrolet IROC-Z with 69k on the ticker
All major and minor routine maintence accomplished less than 2k miles ago
Engine: L98 5.7 liter with accell fuel injectors and hypertech computer chip
Transmission: TH-700R4 (comes with a B&M stage II shift kit not yet installed, should i use it or buy different one?)
Exhaust: Flowmaster exhaust with single high flow cat and 3 inch pipe (A.I.R. equipped headers in route but not installed)
Differential: Unsure if 10 or 9 bolt but has posi....also unsure of gears...believe it has 3.23 or 3.27
Brakes: 4 wheel discs (stock)
Wheels: Stock 16 x 8

The items that are not installed came with the car.

Hopefully I will have a complete list of the RPO codes on the car soon. The window sticker (yes the guy has the orginal window sticker) said that it came with G80 positration but it didn't list the performance axel as an option. This leads me to believe that it is a stock 10 bolt. My last IROC had the 3.27 9 bolt and turned around 2400 rpm at 80 mph. The one previous to it with the 2.78/2.73 turned 2000 rpm at 80 mph. The current owner of the car said this one turns 2400-2500 range around 80 and that is why I believe it has the 3.23 gears.

I am happy for now with the brakes in stock trim. Eventually I will replace them and was considering something along the lines of BAER brakes. For now I think the car stops just fine. Right now I am more interested in performace mods that will help with acceleration.

If you see something that you think I am doing wrong or that could be done better, please be brutally honest. From my reading on this board so far, I do not believe that will be a problem LOL.

These are not listed in any particular order:

Option 1: Mild (2200ish) stall converter that retains the lockup function, change the rear end gear to the 3.42 range..maybe 3.73 (autobahn over here so not sure I want to go too low on the gearing), buy a chip burner and burn a custom tuned chip that will work correctly with the headers and accell fuel injectors (have a friend that can help in this dept)

Option 2: Change the stock 10 bolt/9 bolt out for an aftermarket one...options/prices?

Option 3: New Vortec Heads with the Scroggin-Dickey Manifold and some type of higher performance camshaft (will the LT-4 Hotcam work in L98's?) all 3 of these will certainly bust the $1k barrier...probalby $1500 total?

Option 4: New Throttle body (what type/size?), runners, plenum and some type of cold air/ram air intake

Option 5: Some combination of the above or something suggested by you all

Eventually over the next 6 months I would like to do some combination of all the items listed above. My goal is to approach 400 RWHP. Is that possible with these proposed mods? What kind of abuse will the stock bottom end and rear take? Would I just be better off waiting and putting a Procharger on the car? How would the mods above work with a procharger? I am looking for any and all ideas. Thanks for your help.

This is my first post on this board and I would like to take the opportunity to say this place is far and away the best source of 3rd gen information that I have found.

Jason McGee, SSgt, USAF

 

Welcome. First and foremost, subframe connectors. They help every aspect of the car, acceleration, braking and handling. After that, I'd say get those headers on there before you spend another cent.
To get 400 hp at the rear tire, you'll probably have to lose the stock TPI, and go with a Stealth Ram or something similar. The best thing about the TPI is torque, it builds a pile of it. Anyway, stay away from the throttle body until you are really displacing some serious cubes and power. The injected 502 crate motor comes with a twin 48mm throttle body on it, so I think that you 350 should be fine with the stock throttle body. The hot cam does work pretty good, or so I hear, and it in tandem with a set of Vortec's would be awesome. I was thinking about the Vortec's myself, but I just can't see spending $400 for the Scoggin intake. As far as the tranny stuff, I have no clue. My car is losing it's slushbox and getting a 6-speed.
FYI, seeing that your car is a L98 Iroc, it SHOULD have a 3.2x 9-bolt in it.

 

I forgot to mention the subframe connectors. Thanks for reminding me. I was going to put a set on order, but didn't know what type to buy and how difficult it would be to install them. I definately wouldn't attempt to install them mystlf as the last thing i want is a croocked car.

My current preference is the hotcam, vortec heads, and Scroggin-dickey intake.

The stealth ram looks interesting, but I don't think it will work with vortec head. I have been doing some research, but I have read so much that I can not remember what will and won't work together. One very important thing for me is that the car remains stock in appearance...I do not want to have to replace the hood. Will the Stealth Ram fit under the hood of a 88 IROC-Z?

The headers are being shipped seperately from the car and will be installed at my first available opportunity. I dont have any particular love for TPI, but I would prefer to keep it on the engine if it is possible to get it to the 400 RWHP range.

I am unsure of how the 10 vs 9 bolt was determined. I don't know if it was an option on the 350 cars or standard.

Thanks for the reply...looking foward to many more. It will take the car a month to get here at least. Problems with the shippin company may delay it until april; therefore, I have plenty of time to ponder my options and get parts on order. I could spend as much as $2k but I want to start small and go from there.

I see people that post 'all the free upgrades'. What are they and where can I find more information on them? They must be buried pretty deep in the archives of the board, that or I have been looking in the wrong spots.

Jason

 

They aren't too tough, you just have to make sure the car is supported by the suspension, not the body when you put them in. You can jack up the car, and set jack stands under the front control arms and the rear axle housing. If you still aren't sure, take it somewhere with a drive-on lift, like an exhaust shop.
That is a kick-*** combo, and should make some serious power, but I doubt the 400 rwhp mark with that. It should be into the 400 lb-ft at the matt, though.
It should work just fine under a stock hood. I can't remember if it will work with the Vortec's or not. The stock appearance is something I'm after under my hood too. I don't mean 1987 L98 "as delivered" stock, but more like, long tube runners (check), all accessories (check) stuff like that. My engine has a serpentine cenversion and an air duct from an 89, but it doesn't look out of place under there. Most people wouldn't know anything has been done.
I love the way the TPI looks, and the way it builds torque. It is possible to get to the 400rwhp mark, it's just involved and expensive.
The 9-bolt was standard on L98 cars, and most Iroc's had the decent 3.2x ratio. Some Irocs and most GTA's got the 3.42 ratio, which is pretty nice. The "free-mods are in the Technical Articles section on the front page (right by the links to the Message Boards, Classifieds, etc.).