When someone says "sports car," I generally think small, lightweight, sparsely equipped and slightly juvenile. Likewise, when I hear "GT," I think: quick but not fast, comfort over maximum performance-and dare I say-slightly boring. Steve Dinan has never been one for convention. Equal parts mad scientist and hot rodder in his DNA have led him to build cars that aren't defined by general rules. Sometimes it seems as though they aren't even encumbered by the basic laws of Newtonian physics.

A BMW M6 is at the sportier end of the GT category, but with world-class luxury and handling more appropriate for back road touring than carving up the race track, there aren't many enthusiasts that would call it a true sports car.

To get world-class acceleration numbers out of a 3,900-pound car requires some serious grunt. From the M assembly line the M6 is equipped with a high-strung, 5.0-liter, 500hp V10. Pretty impressive, but with this thing's considerable mass the relatively diminutive 383 lb-ft of torque-peaking at a lofty 6100 rpm-just isn't that much. The stock M6 is quick, but not world-class sports-car fast. Which brings us back to Steve Dinan.

Dinan wasn't interested in forced-induction solutions to this particular problem. He wanted to retain all the feel of the naturally aspirated engine, with its individual throttle bodies for each cylinder, and celebrate the looming end of the second era of big-displacement power the right way. Using his years of experience gained building and racing Daytona prototypes, a plan for stroking and boring the V10 was put in motion.

The crankshaft is a one-piece billet work of metallurgical art. It's possible that a welded crank may have sufficed, but the thought of a welded crank spinning over 8000 rpm gives us all a cold shiver. Pistons are sourced from the O.E. supplier, Mahle. Measuring 93mm, these forged units combine with the 83mm stroker crank to bring the engine to 5.7 liters of displacement. That's 350 cubic inches to you hot-rodders. The block is bored in-house at Dinan's Morgan Hill, Calif., facility, and special care has to be taken to ensure the aluminum-silicon alloy is properly finished for maximum effect. A final honing technique must be used that removes a very specific amount of the aluminum and leaves the dispersed silicon still in place to create a silicon cylinder lining. Connecting the spinning and reciprocating mass are Dinan's proprietary lightweight connecting rods. The whole assembly is blueprinted, balanced, and assigned a Dinan serial number before being installed in a car.

From behind the wheel, the bigger V10 is incredible. The engine sings with a mechanical smoothness akin to a 628hp sewing machine. The power is smooth and gains steadily, there are no dead spots in the curve and it doesn't punish you for coming out of a turn in too low a gear like the factory V10. It revs with the eagerness of a sportbike and even sounds like one as it goes flying by. There's no harshness-even bouncing it off the rev-limiter in first gear it feels like it could probably spin to ten grand if it had the cam to breathe that high.

My first experience driving it involved laying down two smoking black strips using launch control and flashing through first gear faster than I could comprehend. As fast as the car is, it doesn't have the violent feeling usually associated with a powerplant of this magnitude. Power is smooth and delivered completely from normal aspiration. With their enlarged individual throttle bodies, each piston is doing equal work all the time. The current fuel market the way it is, big engines like this may seem politically incorrect. They are inefficient, loud, brutish even, but the experience makes you wonder... if we could turn the moon into gasoline, would we really miss the tides that much?

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