Johnathan Marvin’s ‘87 Buick Grand National

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The Buick Grand National is a landmark car in muscle car history. It’s a classic front-engine, rear wheel drive muscle car, but it got its horsepower from “new” Detroit technologies of turbocharging and fuel injection. That’s why Johnathan Marvin is so stoked about owning this super clean 1987 GN.

When Johnathan and I talked at the Duluth (Georgia) Auto Show, he had owned his Grand National for just a few weeks. But he’s no stranger to turbo power, also owning a Jeep Grand Cherokee Stage 6 Turbo.

In the 1980s, Detroit muscle cars were struggling to meet emission and fuel economy standards. While most manufacturers were putting band-aids on their existing technologies, Buick took a different approach with the Grand National. The GN’s turbocharged, fuel injected 3.8L V6 was a decidedly new way to produce horsepower. In stock trim, the 1987 GN was much quicker in the quarter-mile than that year’s Camaro V6 and only slightly slower than the V8 Corvette.


Like any good hot rodder, Johnathan is taking the Grand National’s solid performance base and making it better. “This thing makes a lot of power,” he told me. “It makes approximately 500 horsepower with the current setup.”

But he’s planning on improving that setup.

The V6’s 3.8 liters equates to about 232 cubic inches, a small displacement in the hot rodding world of 400+ cubic inch big blocks. But the turbocharger and its related equipment are the great equalizer.

The major upgrade to Johnathan’s GN is the turbocharger itself, a Precision 6062 turbo. (The number refers to the 60mm inducer compressor wheel and the 62mm turbine wheel.) Currently, Johnathan is running it at about 25 pounds of boost. He’s got a manual boost control valve in the center console to make adjustments on the fly.

Johnathan also installed a larger intercooler. The intercooler cools the compressed air coming out of the turbo before it hits the intake manifold. Obviously the increased size helps it cool better, but Johnathan is also planning to move it from its current location – between the radiator and the engine block – to a more efficient location in front of the grill.

To further cool the compressed intake air, Johnathan’s GN has an alcohol injection system just in front of the intake plenum. “At high boost, it injects alcohol into the intake,” he explained. “If you cool the charge down, the denser the air is, the more horsepower it will make. And it helps keep the engine from knocking.”

The rest of the intake system includes the throttle body, intake plenum, and individual mechanical fuel injectors in each intake manifold runner. Johnathan is planning to replace the current plenum with a larger one.

I asked Johnathan what was the trickiest part of running a turbo car. “Tuning” he replied immediately.


“Tuning is the biggest issue,” he explained. “If you don’t have tuning knowledge – if you have to rely on someone else – it’s difficult. If you don’t have your fuel / air ratio the way it needs to be, you’ll detonate the motor. Spark timing plays a big key too. You want to retard your timing whenever you make boost.”

As an example of how important proper tuning is, Johnathan explained how on one of his first shakedown runs in the GN, the boost shot up to 30 pounds. “When it hit 30 pounds it backfired through the intake and blew all the vacuum hoses off,” he said. “I’m hoping it didn’t bend the butterfly valve [in the turbocharger].”

One more example: Johnathan’s turbo Jeep Grand Cherokee experienced detonation and broke both the intake and exhaust valve in one cylinder. Not what you want to happen in a $15,000 motor. Yeah, tuning is important.

Once you get past the turbocharged induction system, Johnathan’s Grand National has a lot of go-fast goodies that most hot rodders can relate to. He’s got cast iron Champion heads with ported intakes. The factory electronic ignition has upgraded coils. The original Buick computer will soon be replaced by a stand-alone Holley computer. A low restriction exhaust comes out in a single pipe from the turbo and then splits into duals exiting behind the rear wheels. And all of that is going to get dialed in during an upcoming dyno session at Daffron Race Innovations (DRI) up in Flintstone, Georgia.

The GN’s drivetrain starts with an Art Carr 200R4 transmission and 2500 stall torque converter, and an aluminum drive shaft with a driveshaft hoop. The rear end is factory stock.


Suspension mods include adjustable billet control arms and coilover shocks on the rear, and heavy duty sway bars front and back. Johnathan’s running 15×7 wheels up front, and 15×10 in the back wrapped with Mickey Thompson Drag Radials.

Those M/Ts must be hooking up pretty well at the track, as Johnathan has recently run 12.4, 12.2, and 12.1 quarter mile passes – all while leaving the line on very little boost. “I think the car will run mid 11s leaving at higher boost,” he told me.

One thing the Grand National has that a lot of hot rods don’t is Buick-level comfort. “It’s beautiful,” Johnathan reported. “It’s a comfortable, everyday car.” As you would expect from a Buick, his Grand National has power steering, power brakes, and air conditioning. And, “Everything works,” Johnathan reported with a smile.

The factory interior is in good shape, but Johnathan’s going to spruce it up a bit. The paint is only 8 years old and looks great. Johnathan is planning to complete some minor restoration work to the A pillars and T-tops.

During its six year production run from 1982 to 1987, the Buick Grand National was constantly praised for its innovative technology, strong performance, and good looks. Johnathan’s proud to own such a significant car in Detroit automotive history, but he also knows that a little hot rodding will make a good thing better.


Photos by GHR
Click here to see the photos of Johnathan’s GN.


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