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1990 Pontiac Trans Am - 12 Seconds and 25 MPG

Don Lorentzen's '90 Pontiac Trans Am

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We were desperate for a 12-second e.t. when we wrestled with our '91 Formula Firebird in the June '05 issue. We kinda knew we were on the right track when we made a 14.66 pass with some mail-order bolt-ons, but it was slow going. We finally sprayed the thing to 13.10s with a 150-shot of nitrous oxide and have been tinkering ever since. Third-gen Camaro guys have been abusing us on their Web boards with tales of a naturally aspirated California smog-legal Trans Am that can post a 12.80 timeslip and still get 25 mpg on the freeway. It was everything we wanted our third-gen to be, but the project was tragically discomfited by magazine deadlines and the temporary loss of our shop. Meet Don Lorentzen and the car our Firebird should be.

To be fair (to us), Don used to run Super Stock in the '60s and has been tooling with Pontiacs since he first saw a '62 Grand Prix sitting in a showroom, so he has some experience. "My mouth was watering when I saw that car," he said. "But I ended up with a '61 Bonneville with a 389 and a four-barrel because it was cheaper." That led him to eventually buy a '67 GTO with a Tri-power and a four-speed. "I've always been a four-speed guy, not a cruiser."

Four-speed guy and Pontiac lover, Don wandered through time at his muffler business "on the boulevard" in Orange County until his son Kevin led him back into cars. "My son had his third-gen, and that got me back into it. I found the Trans Am in the Auto Trader with 170,000 miles on the odometer. Originally, it was this guy's wife that owned the car." Yeah, Don, we grappled with the girl-car thing too. It's cool man. Since Don is also a big fan of the Chevy motor, he was also down with the corporate engine on the Pontiac body. He yanked the automatic at first light.

"I've done the factory ('93-and-later Camaro) T56 swap and the Tremec kits directly from the manufacturer. There is a huge difference." After Don retired from his muffler business, he set up shop in a hole in the wall to tinker on fun stuff. The transmission swaps taught him an important lesson, namely the factory swaps aren't nearly as good as the engineered kits you can get from the aftermarket. "The Tremec kit cures all of the problems like the electronic speedometer, offset bellhousing, and you don't have to hack a huge hole in the floor because the shifter plate is about 3 inches smaller than the factory T56."

After the swap, the obvious came next. "When I got into the muffler business, everyone had some kind of engine swap or upgrade. It was just the thing to do." Don pitched the 305 and found a ZZ4 block and added a steel crank, Edelbrock heads, and a street-legal cam. The intake is cut and modified so it resembles a cross between the SLP runners and some original performance prototypes Don showed us in a fuzzy spy photograph. The idea is to increase the peak rpm from the stockish 5,000 or so to up around 5,700. The theory says if the valvetrain can handle the rpm, more is better. Using the Australian 9-inch from an IROC and 3.90 gears, the Trans Am can do high 12s all day-no nitrous, no blower. We're jealous.

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