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My Grand Prix GTPs

Of the 5 W-Body vehicles I've owned 3800 equipped, my 1998 Grand Prix GTP was the one I owned longest, almost 7 years. During that time, it was modified all but for the first two weeks. It went through many different incarnations and combinations.

The first year consistented of the basic 3.4" pulley, open cone air filter setup for the first few months, plus a GrandPrixStore PCM (remember those? That 3.4 presson pulley cost $129 too back in 2001). Back when you were a rebel to run anything under 3.4" pulley, I ran a 3.25 on close to zero KR by doing things that had been rebuted or never tried; things like porting the supercharger myself (I went through a few cases to get things just right), running Autolite 103s when NGK TR55s were THE plug, running a fenderwell intake using plastic plumbing piping to get cooler air, running a 3" downpipe, etc, things that are now common place.

After being one of the first purchase an Intense Stage 1 camshaft, and also one of the first to self port the 3800 SII heads on the forums, I was then one of the first to run Chris White's XP camshaft sold by ZZP. With the XP cam with 1.7 intake rockers, self ported heads with Z06 valve springs, self ported GenIII M90, ZZP's LS1 throttle body kit, self made intake, TOG headers with a custom "Shimmy" dual around the gas tank exhaust system with gutted Shimmy stock mufflers etc, I pulled a record-at-the-time 321 wheel horsepower for highest non-intercooled dyno.

Eventually chipping a piston from running such a max effort non-intercooled setup, next began a lost two years, as I visited two different engine shops to rebuild better and stronger than ever, and both tremendously underdelivering and costing thousands of dollars in the process. The first shop, whom would warranty the motor if fully assembled by them, then failed to take responsibility for a foreign object left in the motor, which destroyed one cylinder on first key turn. Shame because their head ported had touched up my DIY heads, and I had specced a new 224/236 camshaft I was confident would perform. The 2nd shop promised to fix the wrongs of the 1st, but ended up creating their own. Noisey valve guides from a poor head recondition were finally fixed at my expense, only to chip a piston again to discover that the forged pistons I was promised and payed for never went into the rebuild. After installing an L36 block beneath the heads/cam setup, the engine started burning oil, diagnosed once again as their head reconditioning.

After realizing that I'd only build a reliable setup if I started from scratch, and realizing how well the L36 block worked inplace of trying to build a forged piston failproof bottom end, that's exactly what I did. Sourcing yet another and lower mileage L36 from a gentley driven Buick LeSabre, I didn't want to reuse anything I didn't have to. I ported another set of lower mileage supercharged heads and filled them with 5.3 Vortec 1.89/1.55 valve which not only are larger but taller to correct the 3800 valvetrain geometry when running .550 lift and above. These taller valves then took taller LS7 110# valve springs plus matching retainers. The camshaft I resized to 218/234 and swapped the stock rocker arms to 1.7 CompCam mini-shaft rockers; same overall lift as the 224/236 cam with stock rockers, but the 1.7s provided overall faster open and closing rates, plus the roller tip again helps with valve guide wear when running .570 lift. The intake manifold was ported and then ceramic coated, an experiment to keep the heat down. Most importantly, with the help of an associate Darren who was a tool and die guy, the Gen5 based M112 Hybrid was ready for trials, a Gen5 M90 supercharger casing filled with an M112 rotor pack and snout. The beauty was that unlike other M112 setups, this one could reuse M90 intercooler offerings, and sure enough a ZZP fullsize IC is what it sat ontop of, while the LS1 throttle body setup was modified for an 80mm BBK LS1 throttle body. 65# fuel injectors, Racetronix fuel pump setup, TOG headers, a brand new traditionally routed 3" exhaust system with resonator and Flowmaster Super 40s, PRJ fuel rails etc rounded out a setup that made 386 wheel horsepower on pump gas, 18" wheels and through the full exhaust including cat converter.

With the motor running strong but other projects on my 1998 GTP coming due such as a stereo upgrade, seat upgrade, some paint work etc, I realized all could be achieved with the new-at-time 2004+ body style, and that after 2-3 years the 04 CompG package GTPs, top of the line, could be found affordabley. After purchasing a 2004 CompG in spring 2007, the motor was swapped from my 98 GTP into the 04, and vice versa. Items such as the exhaust system were also swapped, a few suspension components, and Redline Transmissions salvaged the input shaft and chainset but otherwise built a new setup for the Tapshift trans. I kept the setup a little more sedate, with quieter Solo Stealth mufflers, factory motor mounts instead of the poly, factory CompG springs instead of lowering springs, things of that nature which made it much more pleasant to drive daily.

Other modifications to the 1998 GTP included one of the first sets of prototype SSC springs with the rear sag fixed, replacing its previous Eibachs, F-Body front brakes, GMPP 34mm front sway bar with Addco 25mm rear sway bar, GMPP trailing arms, Enkei LM-1 18" chrome wheels with Nitto 555 rubber, blackout headlights, Niteshaded rear lights and an SLP Gen1 rear spoiler. Other modifications to the 2004 CompG included an Addco 22mm rear sway bar, Enkei Tarmac 18" polished/gunmetal rims with Nitto Redline rubber, a GM Special Edition front lip spoiler, a GM Special Edition/GXP rear spoiler etc and brand new OE headlights.

During owning these two GTPs, I had also purchased a 1997 GTP with a blown motor and fully rebuilt its drivetrain with an L36 block, my 210/220 SBC camshaft, stock heads, ported M90 and ported 99+ throttle body, ZZP Powerlog and downpipe with 3" cat-back, a full Redline trans rebuild with FDQB converter, 3.29 gearset with GXP dual chains and TransGo shift kit, KYB GR2 struts with SSC lowering springs and GMPP sway bars and trailing arms, F-Body dual piston front brakes and more. A 4th GTP, another 97, was bought for a track car, but parted out instead due to the condition of its body.

My Buick Regal project came later but between the GTPs I owned I had 9 continuous years of supercharged 3800 fun.