Coelacanth's '86 GN


Active Member
Jul 7, 2014
Well, I didn't want to tack on resto or project posts to other people's topics, and I didn't think the Introductions section was the right place either, so I'm creating this thread here to document the evolution of my '86 GN. First, the back-story...I'm 46 now, but 2 or 3 years before the turbo Buicks hit the scene, I was reading about & following the GN in Popular Hot Rodding. I must've been 16-ish. I liked the mean look, but was blown away by the articles on the '86 GN when it was released. My dad was considering a "toy" car at that time, maybe a Camaro or even a Corvette, but those were so impractical to the "family man" with a family & 4 kids...hardly a back-seat, barely a trunk. I encouraged him to check out this Buick car at a local dealership. He had no idea what the GN was all about, I take full credit for bringing it to his attention. :cool:

Needless to say, after the test drive with a Turbo T (the salesman couldn't find the keys for the GN on the lot for some reason), he was signing the pink slips on the GN! That was my first experience of car-buying at a dealership, too...I was all of 17 or 18.

That GN had a lot of history...drove it to my grad, a number of weddings, my younger brother's grad...when the parents were out of town, we'd sneak out and drive it and make mischief, and blow the doors off of Corvettes, embarrassed preppy-boys in their shiny red Camaros, laid waste to tons of 5.0L Mustangs, had a number of Porsche drivers puss out at stoplights...and eventually my dad caught me after recording the mileage. :eek:

Fast-forward to today. About 7 years ago, I bought it from my dad with I believe about 74K kilometers on the odometer. He took extremely good care of the car, never winter-drove it, frequent maintenance & engine shampoos...I knew what I was getting for the family-friendly price of $10,000 CDN. :D The main problem is my dad was starting to drive it like an old man, and the GN certainly wasn't meant to putter by now, although it still runs great, it's quite sluggish compared to how I remembered it.

My dad purchased the car with Centerline clone wheels (15 x 7" with stock P215-65-15 tires) installed...the original GN wheels hardly saw the road other than the drive from the freight truck to the dealership. My dad also had a wing installed on the day he bought it; one of the salespeople recommended it, I believe; a Fiero wing. It actually fits and looks great, and certainly sets the car apart from all the other GN's.

Since I bought the car, I bought brand-new REAL Centerline Auto Drag wheels, I believe 15 x 7" in the front, and 15 x 8.5" on the rear, with P235-60-15 tires to properly fill out the wheel-wells. I always thought the 15 x 7"/215's in the rear were sucked in too far and didn't look aggressive enough. I also added variable-rate springs in the back to stiffen up the rear suspension.

Here's a few pics of how it looks now...


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The car had a few issues that needed to be addressed...the brakes got spongy and I was getting the brake light coming on every time I touched the pedal, so me and a buddy bled the brakes...but the light still kept coming on when the brakes were applied. After researching here on this site, ignorance was the cause. We both figured the Powermaster master cylinder needed to be more or less full, but that kept screwing up the brake system. Once we got the fender-side of the reservoir filled to about 75% and turkey-basted out the motor-side of the reservoir until it was about 25% full (to the low fill line), and I drove the car around the block a bit, the brakes were working perfectly. Dodged a bullet, that didn't cost anything.

The other, bigger issue was the car would puke coolant every time I drove it, even after only 5 minutes. The hoses still looked good, nice pliable I replaced the 180° thermostat with a 160°...that I had to tin-snip & file smooth, down to the correct diameter, and replaced the rad cap with a 16-lb. unit. It still puked after 5 minutes of driving. I was worried it could be the rad, and looked inside; it looked like sugar-frosted Mini-Wheats were growing in rows inside the rad. I scraped at the white growths with a finger and my finger came away with white guck. I figured it was time to replace the rad, it was still the original one. I followed the F-body radiator swap article I found over on and other than the oil cooler fittings I removed from the car being nowhere NEAR the size suggested to buy in the article, and re-routing EOC & TOC lines, it hasn't been too complex of a swap. It's definitely more work than dropping in a $500 (plus shipping to Canada) repro rad, but the $300 or so I'm saving can be put towards modding my intake system eventually.


I took the time to pluck out each and every bug carcass and bits of gravel stuck between the intercooler fins.

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Progress pics of the new rad installed and the engine oil cooler mounted and reconnected. I still have to connect the tranny oil cooler lines...maybe tomorrow night. A few pics of the engine bay how it looks right now...with new rad installed:


I got the tranny cooler lines connected tonight. One thing that's barely touched upon in the F-body rad swap procedure is the need to re-route both tranny cooler lines, there's no easy way to connect them to the F-body rad's tranny cooler fittings. I guess one solution is to throw more money at it and buy an external tranny cooler, and mount it beside the external oil cooler...but I don't like that idea. The rad HAS a tranny cooler built in, why not use it?

Since the original lines won't reach the new rad's fittings, here's how I came up with a solution that cost nothing but a few hours' work and a few choice swear words. Recall that the stock GN rad has engine oil cooler line extensions connecting to 90-degree fittings bolted into the front of the stock rad...I figured with a bit of pipe bending, cutting & flaring, and buying a few 5/16" fittings, I could use those same extensions to mate up to the stock tranny lines. I could've fabricated all new 5/16" tranny lines, but I think that probably would've been even more work than just creatively cutting down and bending those extensions. I'm no expert with a pipe bender, but I managed to get the lines to connect via the OEM couplers with some careful measurements, cutting & bending. This method may seem unorthodox, but it actually reduces the number of potential failure points from 8 to 6 (OEM = 90-degree fitting-to-rad, 90-degree fitting-to-extension, extension-to-coupler, coupler-to tranny line x2; my method = extension-to-rad fitting, extension-to-coupler, coupler-to-tranny line x2).

When it was all said & done, it actually worked out quite nice and looks pretty tidy.


With lower rad hose connected:

View of tranny & oil cooler line routing:
Here's something I noticed that seemed rather odd...when I was reinstalling the black plastic...whatever-it's-called, that directs air into the intake beneath the car into the turbo & first, I thought I'd bolted it on wrong, because there was major overlap obstructing the intake rectangle. When I looked at it from the front, I saw I'd installed it correctly, but that this part obstructs the incoming airflow by at least a good inch or more on either vertical side. This certainly will cause unnecessary turbulence to the incoming airflow so I'll mark it off right where the overlap ends, remove the plastic part and cut each side off by about an inch so the plastic part is more or less flush with the intake rectangle. Has anybody else noticed this?

I'll also have to do something about the floppy part at the top...some zip-ties will hopefully straighten that out.

I got under the car last night, reached up the intake behind the obstructing plastic piece and traced a line where to cut it flush where it meets the plastic piece, with tire marking chalk. I then snapped out the flexible plastic grille, which is very restrictive for airflow...I'll replace it with a steel grille mesh. But it seemed pointless to worry about the airflow being restricted by the floppy plastic grille when I saw this after it was removed:


I tried cleaning out the 28-years-old accumulation of ancient insect parts & greasy road dust with a paintbrush & toothbrush, but ended up just pushing half of the crud deeper into the cooler fins. That wouldn't do, so out came the charge air cooler too. You could hardly even see through it anymore:


It's quite a pain to clean because it's a sandwich of two finned layers; when I'd flush one side with water or compressed air, it would just force the crud onto the opposite layer of fins...but I eventually got it cleaned up. Now you can see through it again! I'd guess the way it was, maybe only 25% airflow was getting through it.

Car wash or pressure washer works on intercooler of not too close.

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Here's some custom work I did to improve airflow through the charge air cooler, and some repairs that needed to be done. Once removed, I noticed one rivet had torn free. I cut it out and replaced it with a nut/bolt/washer with approximately the same diameter threads as the rivet was, and threadlocked it on good & tight. It's not perfect but what can you do, other than buy a new intake section...



I also saw the sections where the...leather? attached & stitched to the plastic were coming loose so I gave it a good cleaning with rubbing alcohol & toothbrush before repairing it with Shoe Goo. That's pretty tough glue and should hold up pretty well, and is certainly better than leaving it alone.


I then got out the hacksaw and cut out the overlapping sections of the plastic fairing that obstruct the airflow into the charge air cooler.


Before/after pic of the intake opening & widened fairing section:


Next thing I had to mod was the floppy plastic grille between the intake hole and the air cooler above. It wouldn't snap into position properly anymore due to the deformation (age probably) of the intake hole, it was significantly bowed out at the top/center. But looking at that plastic grille, it looked like it was actually quite airflow-restrictive. I'll hang onto the original but I figured some kind of mesh would let a lot more air up into the cooler. I found some grille mesh for under $10 on clearance at Canadian Tire. Not only is it much less restrictive, but the mesh is cut in such a way that it has an angle, and I positioned it such that the angle the mesh was cut would actually act like louvers, pulling up air into the intake rather than pushing it down (details, details).


I spent 2 nights fabricating this part to replace the plastic was more work than I thought, but the end results were worth it. I used the original piece as a template. I had to add those 3 ribs to brace it so it was more sturdy than the original piece. I cut them from 3mm Kydex, which is very durable and just a bit flexible; it's used for making bumpers for RC cars and is very tough, and won't stress & crack the way plastic will. I used strips on top & bottom of the grille mesh with strips of automotive double-sided tape to "sandwich" the strips together, then threadlocked on some nuts & bolts. The top center tab and 3 lower tabs all snap into place, but I added some zip-ties to further secure it.

Pictures of the new grille section installed in the charge air cooler; I slapped on the OEM plastic grille to compare how restrictive it is.


Got a lot of progress made but not without a major obstacle. The intercooler is reinstalled and I backed out of the garage to flush out the heater core. After water was coming out of the core clear, I alternated between flushing through the larger (passenger side) tube with water and blowing it out the opposite direction with my air compressor, through the smaller tube (driver's side). I noticed some whitish, slightly milky fluid coming out so I did this about 7 or 8 times until only clear water came out. I then reconnected the rad hoses and flushed the entire system, drained it, then filled it. Drove it back into the garage. No test-drive, because I noticed a solid line of oil on the ground when I'd backed out of the garage. :mad:

It turned out to be leaking from both fittings I bought (as suggested in the F-body radiator swap article on Even after I cranked them on until the fittings were pretty much pressing into the female fittings on the B & M oil cooler, they still leaked like a sieve. One thing that struck me as odd was the fittings I was sold could swivel. That is, the barbed end could swivel separately from the 1/2" NPT threaded end. Is that normal? It originally struck me as odd, as the capacity to swivel seems to indicate there's enough play in there to allow for leaking. Should I have been sold fittings that are solid pieces that don't swivel?

Anyway, on the bright side, I'm liking how the intercooler intake looks now, nice and clean and no airflow obstructions. The widened fairing and grille mesh mods should open up the airflow a tad.

Well, I discovered the reason why the fittings at the oil cooler were leaking; the place that sold me the fittings gave me straight-threaded fittings, not tapered thread (NPT)! I had to cut off a half-inch of the 1/2" hoses, installed 2 *correct* fittings, and they noticeably got tighter the more I wrenched them on. After reconnecting the hoses, no more oil leaks!

A couple nights ago, I spent about an hour and a half with WD-40 and toothbrush removing decades-old accumulated white wax residue from all the cracks, seams, rubber & plastic parts all around the car...that residue had accumulated from the years my dad owned the car, and were impossible to remove with a cloth...had I known WD-40 would remove it so easily and effortlessly, I would've done that years ago! One minor caveat about that, is the WD-40 also removes past wax from the paint, so a good wash & re-wax is necessary. Got that done last night, the car looks better than it has in many years now the the old white wax buildup is gone...back to black!
While I had the grille out for cleaning (and to make sure the universal oil cooler wasn't leaking now that I'd replaced the fittings with correct NPT fittings), I decided that I didn't like the grey-silver center plastic piece contrasting with the black grille and all the other black stuff, so I bombed it with SEM Trim Black and reinstalled it.



Next job to do, when I can do without driving the car for at least 48 hours, is refresh the black paint on the faded-to-grey headlight bezels...

I took care of a minor detailing issue that was annoying me; the headlight bezels, which have faded over the years and have hazing, scuffs and even worn out to show the grey plastic beneath. I removed them, disassembled the corner marker lenses and masked them off, and took care of everything with SEM Trim Black. They look good as new now.

Finally time for an sure takes me a long time to save up a bit of money! Well, last fall I'd all but finished buying up parts to assemble my own air intake. I had a 3.5" LS1 MAF sensor but all the aftermarket intakes I've seen are either 3" or 4" pipes up to the turbo, not 3.5". That was one of my reasons for fabricating my own intake, the other was cost. I bought the 3.5" intake tube, stainless steel 45-degree 4" elbow to mount the 4" K & N cone filter and all the silicone connectors & T-bar clamps for about half the price of the kits available for sale. There was a lot of cutting and measuring and test-fitting, but there's something to be said about doing it all yourself.

For months, my intake project was stalled because I needed an updated MAF translator to work with the 3.5" MAF sensor, and last year, the Axis box & chip I wanted wasn't available for stock injectors. This summer, Eric calibrated an Axis chip for those, so I bought the box & chip combo and took the next step. I also bought an EGR block-off plate and valve cover breather set from G-Body Parts, so I wanted to tackle all those things at the same time.

As always, the things you think will be the most simple, give you the most problems. I pulled out the driver's side breather and the black ring gasket had cracked in 3 places--not to mention the whole thing was slathered on with silicone by some unknown party...I know it wasn't my dad because he didn't do a thing to the car, it was always serviced in shops. I carefully pulled off most of the guck by hand, then used a razor blade to remove what was left from the outside of the valve cover. The new angled breather popped in easy-peasy.




The passenger side breather wouldn't pop in until I removed the bolt holding on that small shield attached to the back side of the turbo first. Removed the hose running to the back of the turbo and installed the rubber block-off plug.
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Picture of the fabricated and assembled 3.5" intake...basically it's a 4" K & N cone filter with 4" stainless 45-degree elbow, 4"-to-3.5" reducer, 3.5" LS1 MAF, 3.5" connector (cut down about 1"), 3.5" intake tube with 45-degree elbow (cut down about 1.5" on the MAF end), 3.5"-to-3" 45-degree angled reducer (cut down about 1" on the turbo end). The removed sections help position the intake tube away from the alternator and allow it to be short enough to tuck the cone filter inside the driver's fender.


Picture of the custom intake compared to stock:


Of course, the charcoal canister had to be relocated; here's my solution. I removed the V-shaped bracket that the stock air filter box bolts onto and saw that the canister could potentially be mounted there, but it was being obstructed from a neat, tidy fit by the steel line & hose that runs to the canister and by the plastic fender shield. I used my handy-dandy tubing cutter to cut down the steel line, which would end up being way too long anyway, added a hose clamp, and cut a notch in the plastic shield to allow the canister to seat firmly in the niche. I was able to use the existing V-bracket mounting hole to bolt down the canister...the hole at the top, in the picture.


Picture showing approximately where I notched the plastic shield, and the canister steel line cut down/hose clamped down:


There's where it sits now; cut down the 2 rubber hoses where they route into the canister as they didn't need to be as long as stock length anymore.

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