At the dawn of the 21st century, General Motors was just a few years away from the infamous bailout. Tight on funds, they were looking for reasonably inexpensive ways to turn their mundane, boring family sedans and trucks into something exciting and inspiring.
They needed to – with the Camaro and Firebird gone, it was necessary to maintain some sort of performance image with potential buyers. As a result, they were seemingly releasing new performance cars just about every day. It was the height of the era of Bob Lutz’s reign; Pontiac had the GTO, Cadillac had the V-Series, and even a Trailblazer could be ordered with an LS2.
Clearly they weren’t leaving any stoned unturned, and Lutz made sure every division (apart from GMC) was pumping out some type of performance vehicle – even Saturn had the Red Line Vue and Ion.
The GM W-body front wheel drive sedans were no different. Sure, there were the L67/L32-powered, supercharged variants from the previous years – but all of them, despite creating a miniature cult following, failed to catch on with the masses.
Lutz felt that a V8 was in order, and helped launch the Monte Carlo and Impala SS, Grand Prix GXP, and the Buick Lacrosse Super – all with LS power! In this case, 5.3-liters of LS4, powerful enough to develop 303 HP and 323 lb-ft. of torque.
The downside was that even though it shared it’s basic LS characteristics with the engines found in the other cars, many of the components were unique to the LS4, thanks to its front wheel drive configuration. Many potential enthusiasts were turned off by this lack of commonality and the fact that it was “wrong wheel drive.”
David Dapp is one of those guys not willing to follow the masses. Obviously a true Pontiac enthusiast at heart as much as any ’68 GTO owner, he took his GXP to the next level by modifying what GM had already created.
Dapp, immediately wanting to rid himself of the Active Fuel Management System (AFM, aka, Displacement On Demand), pulled the engine, and removed it for simplicity’s sake to open up his options when it came time for a camshaft upgrade. That camshaft would be a 218/222 grind with .600″ lift. The rest of the engine benefits from a ported LS6 intake manifold, and Trick Flow Gen-X 205cc heads with a 10.8:1 compression ratio.
Helping the stock displacement LS4 breathe better is a pair of Doug Thorley headers, a cold-air intake, and a Magnaflow exhaust system. An HP Tuners program keeps everything in check, and the 5.3 is backed by a “custom built” version of the factory 4T65E gearbox, while a set of 3.69 gears pull this thing down the track.
Oh, and track times? You can expect 12.50’s at 113 MPH from Dapp’s GXP – it might not be C6 ZR1 performance, but you have to keep in mind that those times were realized with street tires and with front wheel drive. Not bad for a simple top end upgrade and for a car that ran low-14’s stock.