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Published: 8/10/2022

Sweet and Sour: This 1981 Trans Am Features Big Boost



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When you first lay eyes on the yellow 1981 Pontiac Firebird Trans Am built by Jim Miller and his son, Jimmy, both the iconic shape of the car and its famous hood graphics make it easily identifiable. Yet, the car also has a modern look – something the Millers spent a great deal of time perfecting.

Jim Miller's 1981 Trans Am is built to honor the original version, but features a variety of modern touches. The car was a father-son build.


"If it was built today, I feel like this is how they'd do it," said Jimmy Miller during this year's Goodguys Summit Racing Nationals presented by PPG in Columbus, Ohio.

The Millers own Miller & Son Collision, a family operation in Lancaster, New York, which provides not only collision repair, but also restoration, mechanical, and paint services, along with detailing. They live their work, and father and son wrenched on the Trans Am on many nights and weekends after long days of handling customer vehicles.

At the heart of the build is a Chevrolet Performance LSX376-B15 crate engine*, the Bowtie power plant built for up to 15 pounds of boost. The engine in the Trans Am is topped with a Magnuson TVS2650 supercharger.


A Chevrolet Performance LSX376-B15 crate engine* sits under the Trans Am's hood.

"We actually won a partial gift certificate for a Magnuson supercharger (Magnuson then sponsored the price difference), so we knew we needed the best underneath it and Chevrolet Performance had an amazing crate engine," Jim Miller said. "We decided that since it's under a limited warranty†, why wouldn't we go that route? We deal with GM on a daily basis ordering parts for the shop, so it sounded like a great fit. [The engine] was built iron tough and it's got all the best internals in it for what we wanted. We knew that was definitely the building block to work off."

The LSX376-B15 is rated at 473 horsepower and 444 lb.-ft. of torque, but those are simply baseline numbers depending upon the user's forced-induction system. The engine utilizes a cast-iron block with six-bolt cross-bolted main caps, a durable all-forged rotating assembly, and six-bolt, high-flow, rectangular-port LS3-LSX cylinder heads.

"It's got better head clamping [than other LS options] to handle the boost better and not stress anything out," Jimmy Miller said. "There are just a couple of those little trick features with the LSX376-B15 that now appeal to us more so than ever."

Then LSX376-B15 is built for boost. The Millers' is topped with a Magnuson TVS2650 supercharger.


The engine also features a Chevrolet Performance wiring harness and ECM, and the power plant is mated to a Super Magnum six-speed manual transmission. The bellhousing and clutch are from GM as well.

While not purchased as a full Connect & Cruise Crate Powertrain System, the Millers pieced together their own over time.

"We sort of did it as we could afford it," Jim Miller said.

In addition, the Millers installed a Wizard Cooling radiator system known as the LS Beast, made specifically for their application, to help keep the engine cool. They also utilized a Tanks Incorporated fuel tank, which allows for modern fuel injection to be built into a stock-period tank and features a Walbro "Hellcat" in-tank fuel pump.


Jim Miler has owned the 1981 Trans Am for close to three decades.

Jim Miller has owned the car since 1994; when he purchased the vehicle it was a brown color. He soon had it painted a canary yellow, while adding a video game console and TVs. All of this was done before his son was born.

"You fast forward 18, 20 years later and we did it one more time, and this time [Jimmy] did all the metal fab on it and helped me with the whole car," Jim Miller said. "It was kind of cool that I had it before he was born and now he helped me build the whole thing."

Before the car's most recent makeover it had a 455 cubic-inch engine with a four-speed transmission, along with leaf springs in the back and regular coil springs in the front. The factory four-wheel disc brakes remained, as did the factory honeycomb 15-inch wheels.

"We got rid of all that, we've got the best of the best from front to back, top to bottom now," Jim Miller said.

Today, the car features all Ridetech suspension components along with a Ridetech air ride system. Mini tubs and a custom subframe are among the other modifications. A Currie rear end features 4.11 gears.

The Trans Am features a custom interior, which is also equipped with a roll cage.

Upholstery Unlimited in Lancaster, New York, created the interior and the entire concept is based on a rendering from Tavis Highlander and his Highlander Concept Rendering Service in Seattle. The roll cage is from Too Fast Garage, which built the safety system when the car was just a shell on a rotisserie. Other interior highlights include Fessler glass in the front and rear, New Vintage USA gauges, and Vintage Air to keep occupants cool. A push-button start is even included on the center console.

The car's exterior, and a fitting name for a story about this car, is painted in a yellow shade known as Sweet and Sour. It comes from Modern Classikk – a collaboration between Dave Kindig and AkzoNobel. The car also features steel hand-made spoilers, rocker panels, a splitter and a diffuser. Digi-tails provided the LED taillights, and the Millers gutted a shark fin from a Cadillac and installed the GPS for the touchscreen video in the base. It rides on the roof. Their co-worker, Brandon Meek, did all of the wiring throughout the vehicle.

The entire Trans Am rides on Boze forged aluminum wheels measuring 20 x 12 in the rear and 19 x 10 in front. The tires are Toyo R888R sized at 335/30R20 out back and 285/35R19 up front.

An aggressive, modern stance is one of the car's standout elements.

In addition to the upgrades making the Trans Am a prime example of a restomod done right, Jim Miller had another reason for incorporating both old and new elements in the Pontiac.

"Everybody kind of knew us by that car, that's what got us started, was just taking my car around to shows when it was first done," he explained. "That drummed up so much business, I was able to go into business for myself and get out of [working at a] dealership. I wanted to pay tribute to what it was, but just in a modern way."

Another way the Millers looked to pay tribute to the classic Trans Am was by maintaining both the stock-appearing hood and the iconic bird, made famous by a certain bandit.

Maintaining the original graphics on the hood was a painstaking effort.

"The hood was a feat in itself because we had to lower the motor four inches in back just to keep the center of gravity down and to keep that supercharger as low as possible so we didn't have to have an enormous hood," Jim Miller said.

While the LSX376-B15 would've fit perfectly under the stock hood without the supercharger, the Millers went through an extensive process of fabricating their own version of the hood, painstakingly cutting graphics, and modifying components underneath the car to ensure everything looked original. CJR Machining in Alden, New York, helped with much of the process.

Jimmy Miller (left) with his father, Jim. The two built the 1981 Trans Am together.


At Goodguys Columbus, the Trans Am participated in the Chevrolet Performance Builder of the Year program along with appearing in the Ridetech booth. The Millers are veterans of a wide variety of shows to showcase the build's sponsors, but neither had been to the Columbus event.

"It's my favorite show we have ever been to, a great show," Jimmy Miller said. "The way the show was laid out was probably my favorite part, and there were so many elegant, classic cars."

"Just top-notch," added his father.

You can count their Sweet and Sour Trans Am in that category.

Keep watching The BLOCK for much more on Chevrolet Performance builds from across the nation.


*Because of its effect on a vehicle's emissions performance, this engine is intended exclusively for use in competition vehicles. This engine is designed and intended for use in vehicles operated exclusively for competition: in racing or organized competition on courses separate from public streets or highways. Installation or use of this engine on a vehicle operated on public streets or highways is likely to violate U.S., Canadian, and state and provincial laws and regulations related to motor vehicle emissions

†Chevrolet Performance Crate Engines include a 24-month or 50,000-mile/80,000-kilometer limited warranty, whichever comes first. See your GM dealer for details.