Buick Grand National 1986 images

A year after the 1986 Grand National, Buick quietly built something even more extreme, just 547 of them, each pulled off the line and reworked by an outside performance shop. This piece covers the 1987 GNX’s real story: the upgrades officially listed, the horsepower Buick would not put on paper, and how a turbocharged Buick ended up outrunning cars that cost three times as much.

For the 1986 model year the Grand National has a completely redesigned engine with an improved turbo-charger. The computer fuel management system has been greatly improved, and, along with a large number of other lesser upgrades to complete the package. The Gran National luxury muscle car is under-rated by Buick at 235 hp (175.24 kW) developed and 335 lbs (454Nm) torque is put to the wheels.

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Buick called the 1986 Grand National’s turbocharged V6 “under-rated” right there in its own literature — and one year later, the company proved it by building something even angrier out of the same basic engine. Only 547 of these next-generation cars ever existed, each one pulled off the regular assembly line and handed to an outside shop for a transformation Buick’s own factory wasn’t set up to build. What came back was fast enough to worry Ferrari and Porsche owners who never expected a Buick to be the problem. What exactly did that shop change?

Only 547 Cars Got the Full Transformation

The 1987 GNX — Grand National Experimental — started life as a standard Grand National with the usual interior, then went to American Specialty Cars, working alongside McLaren Performance Technologies, for a complete rework. The changes included a Garrett T3 turbocharger fitted with a ceramic impeller and a dedicated GNX heat shield, a larger-capacity intercooler, reprogrammed engine management, a performance suspension with a torque-arm bar, and a GNX-specific rear differential cover. Just 547 cars received the full conversion, making it one of the rarest turbocharged Buicks ever built.

The Numbers Buick Wouldn’t Officially Admit To

Officially, Buick advertised the GNX at 276 horsepower and 360 lb-ft of torque. Independent testing told a different story, putting real output at more than 300 horsepower and roughly 400 lb-ft at 3,900 rpm. That translated to 0-60 mph in under five seconds and a low-13-second quarter-mile — quick enough that the GNX genuinely worried owners of contemporary Ferraris and Porsches, and it’s still remembered as one of the fastest production cars of its entire decade.

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