Flow GTO - Project Car
There's a certain autonomy afforded aftermarket industry insiders-it's the liberty to rip apart brand-new cars and throw everything at 'em in a manner that few real-world rodders could afford, all in the name of product development, PR value, being the first to find the car's limits, and just plain goin' fast on the company dime. So, when we ran into Flowmaster's Kevin McClelland at the '03 SEMA Show and he told us that the company had ordered one of the first '04 GTOs from Wood Pontiac, we told him we wanted to tag along.
Then there's the reality of the aftermarket life, which is that hot rodding doesn't always go exactly as planned. If you recall our first announcement of the Flow GTO in the Project Garage section of the July '05 issue, you'll know that the wild scheme involved creating the first twin-turbo LS6 '04 courtesy of Turbonetics. Then there was the reality that Flowmaster's long-term goal was to return the car to stock and give it away, a plan that lawyers frown upon when you've hacked away most of the car's inner fender supports to clear turbo plumbing. Long story short, McClelland got plenty of practice yanking engines in and out of the Goat. It ran Power Tour(tm) 2004 with a stock mill. The plan was changed from boost to nitrous, and the end result is slightly less radical but more of a real-world example of something more guys might duplicate at home. And it's another fine example of the prowess of those glorious Gen III engines.
The engine started with a GM Performance Parts LS6 crate engine, but it was rebuilt to accept advanced power levels, starting with a set of CP forged pistons to lower the compression to 9.5:1 (10cc dish), provide more valve-to-piston clearance, and withstand the nitrous hit. If you have never seen a CP piston, you should-they are of spectacular quality. These were loaded with Total Seal 1.5mm/1.5mm/ 3mm rings, then the engine was reassembled with ARP fasteners, including head and main studs and rod bolts, thereby eliminating the stock torque-to-yield stuff. Oiling was upgraded with a blueprinted Katech pump. The heads were swapped for GMPP's CNC-ported versions of the LS6 heads with Cometic gaskets, and the cam was a prototype for Crane's Z-series hydraulic roller, PN HR-220/3241-2S-13, featuring 220/228 degrees of duration at 0.050-inch tappet lift, 0.551/0.551 lift, and a lobe displacement angle of 113 degrees. Crane springs and seats, titanium retainers, and a stud-mounted roller-rocker kit were also used. Other than a blueprinted Katech throttle-body and the essential Nitrous Express direct-port kit, that was it for the engine. Katech's Mark McPhail helped retune the factory computer.
A Centerforce Dual-Friction clutch was hung on the flywheel as the LS6 was loaded back into the car, and McClelland fabricated a set of 131/44-inch headers from GMPP flanges and Burns Stainless components using Flowmaster-style merge collectors and Flowmaster Super 40 mufflers in a custom 3-inch system. A heat shield was fabricated to separate the air-intake ducting from the heat of the radiator. That's when the chassis-dyno testing began-the numbers are included in the chart. The biggest surprise came in an A/B test of the stock intake ducting versus a K&N FIPK system (PN 63-1099); the K&N was worth 38 flywheel horsepower! That's a huge number, and it's likely so because the modified LS6 has a greater air demand than the stock LS2, but we still say the K&N kit is something any GTO owner should consider. In its final tune-up, the combo made 381 rwhp (479 flywheel horsepower) at 6,100 rpm naturally aspirated, and with a full load of Nitrous Express juice, it hit 564 rwhp, which converted to 701 flywheel horsepower on the Flowmaster chassis dyno.
Can it handle the power? The Flow GTO still runs the stock trans and rearend, and the only chassis mods are Hotchkis springs and Baer brakes. Per McClelland, "There's nothing inherently wrong with IRS if someone would just work to get the geometry right. But as it sits, the geometry's not right." As a result, it wheelhops like a mother, and McClelland granny-shifts the B&M stick to save parts. Even so, even in Long Haul(tm) trim for the '05 Power Tour(tm), and even weighing in at nearly 4,000 pounds with driver, and even on 275/35XR18 Nitto NT555 street radials, and even in the heat of the day, the car ran 12.45 at 121.81 mph at Indianapolis Raceway Park during Power Tour(tm). Back home in Sonoma, California, it has gone as fast as 123. You'd like to see a little better e.t. for that mph, but at least the car-and especially the rear halfshafts-are still in one gleaming chunk.
Flow GTO Rear-Wheel Power All MotorOn The ButtonRPMLB-FTHPLB-FTHP3,5003362243322223,6003352293242243,7003342343 282313,8003372443962893,9003402524483334,000342260 4943734,1003442705304174,2003482785364294,30034928 55424414,4003542955544674,5003593095584794,6003603165644914,7003573195635064,8003553255625134,90035433156 05195,0003513335545285,1003503415515325,2003483455 445395,3003463485395425,4003443545305465,500343358 5235515,6003403635215555,7003393675135595,80033837 35055615,9003353775015626,0003323784935646,1003283814845636,2003223814745626,3003163784635586,400309377435529

Photo Gallery: 2004 Pontiac GTO Flowmaster Project Car - Hot Rod Magazine



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