If you love cars and spent the better part of your youth in the 1980s there’s no more mythical performance machine than the GNX. With all the mind bending, awesome Mopar stuff that Gary and Pam Beineke have built over the years, we wanted to show you their one non-Mopar ride. They may not have built this one, but they drive it, care for it, and totally appreciate what it means in the scope of domestic performance car history.

There’s really nothing to hate on these cars stylistically. Even the fender vents are actually functional, releasing hot air from under the hood and, in the hopes of the engineers who fought for them, making the intercooler more effective. Beineke says that you can see the heat coming out of them after the car has been running for a while.

This was about the last vantage point you saw as the turbo was getting spooled up. The next thing would have been the tail lights as the black Buick swallowed you hole at the street races. The 547 produced stand as a defining example of just how good a performance car can be done when a company is allowed to follow a plan without being forced into a constant set of compromises.

Seeing this emblem in 1987 would elicit two responses. The first would be the person rubbing their eyes, and the second would be them running away in fear. Think about how big a mind bender this car was back then. Magazine testers recorded elapsed times in the 13.2-13.4 second range. Corvettes were 14-second cars then. Many of the 547 examples have never seen the light of day, but Beineke has driven this car more than 8,000 miles since he bought it new.

A common misconception is that the GNX has a motor that’s been beefed up all kinds of ways beyond a standard GN engine, yet it's exactly the same as those found in Grand Nationals. We’ve heard that there were early considerations of pulling them apart and blueprinting them, but that idea never made it past the planning stage. What’s changed is a lot of the stuff bolted to it. The turbo is an upgraded T-3, the intercooler is more efficient, the EMC calibration has been optimized and boost was increased to 15 psi. The motor was officially rated at a laughable 276hp and 360 ft/lbs of torque.

Here's a great way to tell you are looking at a real GNX. This is the plate on top of the intercooler. It’s got all the pertinent info necessary for ID. No plate? It’s a forgery.

This sticker is a good tell tale to check for when you are trying to determine whether or not the car you are looking at is a real GNX.

Hiding under that heat shield is the upgraded Garrett T-3 turbo. It was upgraded with a ceramic impeller wheel to reduce turbo lag and the turbo was also given a trap to catch any debris that may try to make it through the turbo due to the increased boost pressure. The GNXs were the only cars to get the trap. Also you can see the intake pipe coming up from the intercooler that was coated with a special heat resistant paint to keep the intake charge as cool as possible.

The wheels are GNX specific. They are 16-inch-diameter pieces and of a specific “honeycomb” design. The front and the rears are of different offsets. Front tires were 245/50/16 and the rears were 255/50/16. These lightweight wheels are different from the similar looking wheels used on Pontiac Firebirds of the era. Because of the larger rolling stock, the fenders were cut and molded plastic fender flairs were added to both enhance the look of the car, and keep all that rubber inside the fenders. Center caps were sourced from Pontiac and modified.

The biggest change to the stock interior over a run of the mill GN is the instrument cluster which was completely revamped. GNX models were equipped with six Stewart-Warner gauges measuring all the normal functions, including boost. Pretty classic 1980s G-body plastic just about everywhere else.

Although the front suspension is totally the same as a standard GN, the rear is where the magic happens. The first thing that catches your eye is the big, GNX specific, rearend housing cover. It’s a cast aluminum piece that is there to act as an anchor point for the ladder bar. A real GNX has no upper control arms, as they were ditched for the ladder set up. The front of that ladder bar is mounted to a custom square-tube steel crossmember that also acts as a driveshaft loop. That crossmember was added by ASC/Mclaren to improve rigidity and to maximize the weight transfer ability of the ladder bar. Because the upper control arms are gone and only the single ladder bar remains, the panhard bar was necessary to keep the rearend from moving laterally.

With all of the impressive engineering that went into these cars, you’re probably wondering why the mufflers are all smashed in at the corners. We were too, until Beineke explained that they are supposed to be that way. He actually called Buick upon seeing the car up on a lift to request a new set of mufflers and he was referred to an engineer at ASC/Mclaren. He was the told that they had to smash the corners of the mufflers in to clear a couple of suspension parts. Normal GNs have a single transverse muffler, not the duals. After trying to source stock mufflers from a couple places, the quickest and easiest solution was to use a hammer and a block of wood to replicate the dents.

Believe it or not, the GNX was equipped with drums in the rear. They were special in the fact that they are aluminum. Beineke said that he has had to pull them off the car at least once as they like to accumulate that powdery white corrosion that all aluminum parts do after having been exposed to the elements. The rear bumper inserts are also made of aluminum, a move that was rumored to have pulled as much as 25 pounds off the rear of the car over the steel examples. Just don’t get rear ended.

The intercooler was upgraded as part of the GNX package with a unit that has a denser fin count to help remove heat more efficiently. We dig the crank pulley mounted fan that pulls air through it. Note the large front sway bar that still has the installation tags on it from the factory. The transmission is a factory upgraded 200-4R unit that has firmer shifts. The torque converter is the same as would be found in a normal GN.

Neat detail on how the front air dam is reworked to accommodate the large opening for the intercooler.