2002 Pontiac WS6 Trans Am - Flashbacks

The '70s are long gone, and you'd be hard pressed to find a muscle car made in the last ten years with anything as stout as the old Pontiac 455s. As the years have advanced so has technology. Large displacement has become almost pass-being replaced by more modestly cubed forced-induction motors. But as Jon Obrizok reminds us, there really is nothing like the visceral grunt of a big cube motor with a big cam inhaling only unmolested atmosphere.

After several years of saving enough money to own a 10-second Trans Am that would harken back to the early '70s models using 455 cubic inches of naturally aspirated grunt, the day has finally come when Jon can sit back like a proud father and watch the smoke pour out of the wheel wells. The 21-year-old excavation equipment operator didn't reserve his elbow grease for just the job site either, as he and his father Bob rolled up their sleeves and put together the entire car including the sleeved and stroked LS1. The machine work was one of the only aspects of the build the two farmed out. Race Engine Development in Oceanside, California, was commissioned for that task and to install Darton 4.200-inch MID sleeves. The freshly decked and align-honed block was shipped back to Jon and Bob's garage in LaGrangeville, New York (just outside Poughkeepsie), where a forged, fully balanced Lunati 4.125-inch stroke crank, Lunati Pro Mod billet rods, and JE custom forged pistons awaited. After the block and windage tray were clearanced for the extra stroke, the beefy rotating assembly was installed with ARP main studs.

The LS cam gurus at Thunder Racing selected a lumpy hydraulic roller for Jon and Bob to insert into the assembled shortblock measuring a whopping 248/252 duration, .615/.625-inch lift. A refurbished set of stock 1.7 rockers were acquired from Harland Sharp to activate 2.08 and 1.60 valves with Comp Cams 921 springs on a set of Air Flow Research 225cc heads (with 76cc combustion chambers). Using Cometic MLS MID, big bore-specific head gaskets, the compression ratio equals 11.2 to 1, matching perfectly the 93-octane speed density tune from Brian Reese (discussed elsewhere in this issue). The naturally aspirated motor requires only a set of Bosch 42-pound injectors and a Walbro 255lph in-tank pump to keep up with the fuel demands, while the stock ignition proves sufficient. The stock cooling system was not, however, with the thin wet MID sleeves that can develop holes over time from cavitation. Evans NPG-R coolant actively prevents cavitation and also increases the boiling point, which helps reduce detonation due to the decrease in hot spots. An Evans water pump vastly increases the coolant flow and distribution as well, which Jon says was much needed for an engine of this size-as the right bank can become starved over 5000 rpm.

The intake air tract benefits from a MAF-to-MAP Speed Density conversion by Brian Reese, and also has the benefit of an SLP airlid, Nick Williams 90mm throttle body, and a painted FAST LSX intake. Appropriately sized 225cc AFR heads feed the gargantuan 455ci home-built LS1 outfitted with Darton MID wet sleeves from Race Engine Development. The stock computer and a hefty 248/252 duration cam from Thunder Racing control combustion, while an Evans Cooling System high-flow water pump and coolant keep the thin sleeves from turning to Swiss cheese.

Jon didn't want to mess around with any bottlenecked stock-style exhaust that might produce a raspy exhaust note, so he drove over to Kooks Custom Headers for a custom true dual exhaust setup. It took about 12 hours to produce these beautiful polished 304 stainless pipes that utilize an X-pipe, two resonators and two mufflers without a hint of rattle-which also hugs the floorpan perfectly. In combination with Kooks 1 3/4 to 1 7/8-inch stepped long tube race headers, the TA produces an intimidating low rumble, even at idle.