In GM Performance Parts' Latest endeavor to test out its products and show the world the wonders of LS power, it chose two in-house 4L60E-equipped F-bodies as the recipients of its latest and greatest crate motors. Sure the LS7-powered Goat and Camaro of last year ran like a brown bunny on crystal meth, but what happens when you bolt up one of GM's most popular four-speed automatics to an LS7 or a hopped-up 454-cube LSX motor?
That's exactly what GMPP hoped to find out when two former development cars, a GMMG 427 SS and a Collector Edition Trans Am convertible, were procured to test out several new prototype pieces soon to grace the pages of its catalog.
The Hugger Orange 2002 SS was originally a test vehicle, converted to GMMG ZL1 specs to develop a 4L60E-based trans capable of handling over 600 hp. As the result, it came to GMPP with a carbon-fiber high-flow air lid, chambered exhaust, and many unique aesthetic touches, such as the ZL1 stripes that adorn the fenders. The suspension and brakes, though, appear to be untouched. While the stock trans may have held up to 325 hp in stock SS trim, it had little chance of withstanding an LS7's punishment. The folks at GM Powertrain removed its guts and stuffed the casing full of heavy-duty 4L70E components, as well as a Corvette accumulator, and matched the trans to a '06 GTO converter. Just what, pray tell, is a 4L70E and what car does it come in? I guess we will have to wait and see ...
Now that the trans could contain it, the chassis was prepared for the addition of the dry-sump motor. The battery was relocated to the trunk, and the oil tank mounted in its place. A 3.73 ring-and-pinion replaced the factory 3.23 ratio for improved performance and to simulate a typical customer modification. Meanwhile, the factory LS1 computer was swapped for an E67 computer and harness that GMPP is producing to complement its Gen IV crate-engine line, which is compatible with the 58x reluctor wheel, relocated knock sensors, and electronic throttle. The SS was not unlike most any other application, in that using this setup meant rigging an electronic gas pedal and constructing a custom gauge cluster (since the E67 is not compatible with the factory electronics). GMPP's catalog of gauges came in handy for fabricating the new cluster, which added a custom look to the otherwise unmolested interior.
Aside from running custom oil lines from the oil tank to the dry-sump oil pan, no extra effort was required in bolting up the LS7 to the factory K-member and stuffing it back into the engine bay, as well as affixing all the accessories. The stock 427-cube crate engine came with ignition coils, intake manifold, fuel rails, injectors, and even exhaust manifolds. However, for a slight bump in the previously rated 505 horses, Stainless Works long-tube headers and Y-pipe were mated to the GMMG exhaust. With a custom calibration to the PCM, the LS7 runs flawlessly like an OEM motor-just with a little more bite.
In addition to helping put together the SS, Thomson Automotive played a big role in building the more highly modified Collector Edition Trans Am. Though the TA is believed to be a 2000 model that began its life at GM as sort of a prototype for the Collector Edition-it was born again with fresh paint and graphics to modernize the CETA look. At Thomson, 18-inch C5 Corvette wheels replaced the black WS6 rolling stock in order to fit a set of Brembo Gran Turismo four-piston front brakes with 13-inch cross-drilled rotors. The WS6 suspension was enhanced by BMR Fabrication's subframe connectors, torque arm, and transmission crossmember.
While the stock transmission was sent out for the same treatment as the HOSS, Thomson swapped the LS1 for a prototype 454-cid LSX crate engine. Using a 4.185-inch bore and a 4.125-inch stroke, the small-block achieved maximum displacement with a forged, high-compression rotating assembly. Topping off the 11:1 compression short-block is an LS7-style variety of the six-bolt LSX line of heads GMPP plans to unveil, hopefully some time before Christmas. Stock LS7 titanium 2.20 intake and sodium-filled 1.61 exhaust valves are commanded by stock LS7 rockers and a prototype GMPP 236/246 duration cam with 0.630-inch lift and 110LSA. This is the very same combo used in the 454 LSX in Reggie Jackson's '69 Camaro. But unlike Mr. October's motor, this TA was staying EFI all the way. An LS7 intake, fuel rails and 55-lb/hr injectors give precise port injection and great street manners, though the plastic intake impedes top-end flow enough to keep the motor below the 640 horses Jackson's motor made with the Holley carb and GMPP intake.
Little restriction was left on the exhaust side, as Thomson fabricated 2-inch primary headers with 3-inch collectors, a 3-inch off-road Y-pipe, and a custom axle-back exhaust. The stock fuel pump was sufficient for the naturally aspirated motor, as was the factory computer, harness, and sensors with the GMPP LSX block. An MSD 90mm throttle body with a fabricated bracket mounted on the passenger-side cylinder head made retention of the stock cable throttle and computer possible, along with a 24x reluctor wheel on the crank. A custom tune was needed, but the stock ignition coils and accessories made the grade.
The TA, like the SS, is an example of one impressive solution to the power crisis with aftermarket performance in a factory package. Whether your flavor is the warranty-backed 505-horse LS7, or the more snarling 630+hp LSX, GM Performance Parts has you covered. And now that they have shown us how, it's up to you to decide the when and the where.