Showing some love to the GN - Time for updates - Looking for Advice


TRs on the Brain
May 25, 2001
What I'm looking for:
I'm finally going to dedicate some time and money to the GN again after a fairly long rest (other than the Hydroboost swap). I'd like to have a quick street car that rides and performs well, something I can jump in, drive anywhere, and travel in fairly rapid comfort. I'm not looking for an all-out racecar or to do extremely significant mods (no full engine rebuilds, tubbed rear end, or massive turbo setup). I'd prefer to not tear into engine internals too much or do things that are not reversible in the future.

What I have:
I've got a relatively basically modded 87' GN with 62k miles on it. It's been hibernating for a bit but is started and driven around the block regularly. Of course it leaks oil and needs new valve cover gaskets, rear main seal, and probably valve springs and timing chain. It has a hotwire kit with an upgraded fuel pump, I believe a Walbro 340, 009 42.5 lb. injectors, a Turbonetics Cheetah Stage 4 (from what I was told) turbo, 2800 or 3200 rpm PTS converter (not sure on stall speed), a Scanmaster 2.1, Turbo Tweak chip, Hooker stainless exhaust, rear seat braces, and poly body bushings all around. It has also been converted over to a hydro boost brake setup with a PSC reservoir and will most likely have the power steering pump overhauled and adjusted this winter. There are some other minor mods I'm sure I've forgotten to list. I have done the spring cleaning, replaced the brake combination valve (need to fix the leak now), put on new tires, and covered most of the basic maintenance items.

What I'm considering:
Valve springs
Timing chain set
Valve cover gaskets and rear main seal replacement
Air conditioning system overhaul
Turbo upgrade (very lost here, would like something that matches my setup better and spools faster)
MAF Translator and LS1 MAF
Scanmaster G
Wideband O2
Electronic boost control
E85 Flexfuel conversion (E85 is widely available near me and the car doesn't normally do long trips)
ECUGN (I know this is a major upgrade but I'm trying to determine if it makes sense to jump into this for the extra features given the cost to do MAF translator, MAF, Powerlogger, Wideband O2, Boost Control, and E85)
Suspension / brake upgrades (Don't need autocross but I do enjoy corners and arriving at the exit of one safely)
Anything else I have missed

I appreciate any thoughts or suggestions on how you think I should proceed based on my goals. Recommendations for general priorities up to specific parts and vendors would be great as I don't know all the details of what's available or what's considered to be good like I used to a decade or so ago (I do know about some companies being under new ownership). I'm really looking for ideas on the best way to build a quick, enjoyable Turbo Buick that's not too far from stock but takes advantage of 35 years of development and refinement. Thanks so much all, it's great to think about driving an improved version of my GN again in the spring and getting to really enjoy it after too many years in the garage.
Valve springs are easy, need the rocker arm tool, valve springs and a handful of extra keepers in case one or two go flying. Comp Cam 980-12 springs unless someone knows better.
Use cork valve cover gaskets, not sure about rear main as I never did mine.
Not sure you need a turbo, the chip and injectors may handle the spool issue. Your converter sounds good also.
Big fuel pump, I have Walbro 450, others may differ in opinion.
Likely you will need a larger return line, 3/8" will be fine, I bought mine from Cruz Performance.
Adjustable fuel pressure regulator.
Racetronix fuel pump harness.
Turbotweak E85 chip and 120lb injectors, don't skimp. You can get a 93 octane chip also for emergencies in case you get somewhere and are almost out of fuel.
Pypes Race Pro 2.5" cat back exhaust is plenty and sounds good, its a good kit but I added stainless band clamps instead of the U bolts so I did not crimp the pipe. You have to buy the clamps on ebay or elsewhere.
Everything else sounds like good stuff, I would stick with the stock computer unless you really want a stand alone.
I would guess you are going to spend around $3000 for everything wrenching yourself but it will be nice and reliable. Its not cheap date. Shop around and ask questions.
I’d definitely go for the ECUGN and do it as one of the primary upgrades. It enables everything that you want to do to the car. The flex fuel, ignition upgrades, fuel system upgrades. You won’t need MAF sensors or translators or TR6 modules, you won’t need modified stock ECM or chips for different fuels or injectors, you won’t need a boost controller. The ECUGN can support everything you’re looking to do and provides additional important features like AFR safety, over boost protection, and fuel pressure safety to prevent catastrophe when something isn’t right.
Agree with BeatAV8 on the GNECU. By the time you buy all of the other stuff you are close to what the GNECU costs and the wiring is much cleaner with the GNECU. And add in the Scanmaster G. For the suspension start off with the HR rear sway bar for starters. It makes a big difference in ride and cornering.
As I see other peoples point
No disrespect intended
I do disagree on the ecm
And feel other needed things that go with an aftermarket computer systems weren't brought up.
For this stock motored car bolt on car
Axis computer and chip ls1 maf would be the most I would spend on it.
Heck a tt chip could do it.
Most of the other stuff is a wash money wise as that would be needed anyway like external gate wideband etc.
Turbosmart electronic boost controller which has safety features like overboost protection(350/400$$) and the ability to control ramps.
The stock ecm and 120$$ tt chip can easily handle this combo and you would be saving 1000s of $$ to put in other places.
Remember aftermarket computer systems dont install themselves nor do they tune themselves😉
Also in my personal opinion if your spending 2000$$ plus the install and a tuner to tune it aftermarket wiring should go with that
Which adds alot more to that gnecu.
The axis with the axis chip will tie into maf sensor so tuning is easy
But axis is more money.
But it's not bad on the install and still saves 1000s of $$ and doesn't require dyno tuning.
Or run a tt chip 5.7 and tune off the wideband.
Your stock motor bolt on combo will limit power which limits turbo selection to 64mm or less.
You would be smarter and save $$$ taking weight out running a stock ecm and electronic boost controller.
And spending the time and $$ getting the car to work and set the suspension up to work in the environment you want to go fast in.
You will need someone for that and it takes $$.
X2 on the Comp 981’s, they will soften up by at least 10 lbs after 1st heat cycle
I put the comp 980's in my 86 when I was planning to "only" run 15-16 psi of boost. After getting bit by the boost bug I found that with my current setup I am not making any additional power above 29psi and I know the turbo is not all in yet, it has more left. I was seeing nice gains at the track when making small increases of boost starting at 24psi but hit a ceiling at 29psi. I'm convinced its the valve springs and if I were to do it again I would go comp 981's.
If you have e85 readily available I wouldn't bother trying to run lower quality gas mixed in. Get a TT e85 chip and step up the fuel pump/ injectors to support it. You can dial it in easy enough with the chip by using the scanmaster and wideband data to have a really good running street car. Do the MAF translator and LS1 maf, valve springs and fix oil leaks. Keep it simple. Play with the timing in the chip to help that turbo spool and if it's still too laggy, go with a modern 58mm turbo upgrade. When I was running e85 and a TE44 turbo the response was almost too fast for street tires.
I'd just pull the engine out, it is easy after the first 5 or 6 times. Drop the oil pan and fix the oil leaks and new valve springs. Then address the issue at hand with what you have, you probably have a issue with the internal wastegate bleeding off or turbo mismatch. A 3000 stall at 0 psi boost should be a blast on a TE44 or smaller turbo. I'd just put in an external wastegate on a spring and bleeder setup to see if can just get what you have working better.
I really appreciate the opinions all! Here's where I'm at:

I have a set of Comp Cams 981 valve springs sitting in the garage waiting for install. I haven't bought a rocker arm tool or extra keepers, any suggestions or part numbers for those?
What timing chain does everyone recommend? I've seen plenty of recommendations for both the Rollmaster and the TA Performance. Should I plan on the stock length or undersized?
What should I do along with the timing chain while I'm in there? Cam button? Tensioner? Anything else?

I'm still undecided on the ECU GN.
If I were to go E85, what fuel pump should I be looking at? Are larger return lines necessary and if so, is there a certain set that's preferred?

I'd love to pull the engine and make everything easier along with having access to really get things cleaned up and sorted. I'm having surgery in a couple of weeks and will be down for a couple of months most likely, so if I go that route it will be a late spring project, which is probably where I'm at anyway.

I really appreciate everyone's help, thanks so much!
You need to decide when the upgrades end😉
If you want to do e85
I would do all new lines and pump.
If you dont want to do that.
Buy an alky kit and just replace the in tank pump.
I would pull the tank down,check your lines fuel rail and flow your injectors 1st and if that's all good go alky.
If not then go with ptfe lines and revamp the fuel system.
I run e85, 120 inj, hellcat fuel pump, stock fuel lines, ecugn, ecugn controls fuel pump, Colorado coil. 6262 turbo. No problems at all including fuel pressure.
Well.... since no one has brought up the subject of his transmission.
I will ask Mr. stang, is your transmission up to the task that will soon be asked of it?
If not,it soon will be.😏
Well.... since no one has brought up the subject of his transmission.
I will ask Mr. stang, is your transmission up to the task that will soon be asked of it?
If not,it soon will be.😏
It has, thanks for pointing that out. Level 10 went through the trans many years ago, before my ownership, and gave it the street / strip treatment. I was told that made it good for high 10s but I haven't seen the actual bill of work in years (I have it somewhere) to verify exactly what was done.