IF YOU AIN’ T CHEATING, YOU AIN’ T TRYING
Tommy Riggins’ 1983 Chevrolet Malibu
When IMSA tied minimum weight and engine capacity together in its Kelly American Challenge, Tommy Riggins’ Chevy Malibu was adapted to race as a featherweight
What’ s the USA’ s official motto?‘ In God … something.’ No.‘ There ain’ t no replacement for displacement.’ Ahh yes, that’ s it. Well, back in the late Seventies and Eighties, in the Kelly America Series, too many cubic inches gave you a weight penalty. So, against everything the Land of the Free stands for, there were actual benefits to a smaller capacity engine. Tommy Riggins, however, wanted both a big thumping V8 and a lightweight Chevrolet Malibu.
Between 1977 and 1989, the International Motor Sports Association( IMSA), a prominent North American motor sport sanctioning body, created a series to support its main GT races, something that would also‘ promote interest in American-built, volume-produced sedans’. It was called the Kelly American Challenge. It was for American-only‘ stock cars’ on‘ road circuits’ – to us Europeans, that means cars that broadly looked like factory cars but are significantly modified for racing and tracks with left and right turns. You’ d see Pontiac Firebirds against Chevrolet Camaros, Mercury Capris, Oldsmobile Cutlasses, Buick Skylarks, Dodge Aspens and Chevrolet Malibus.
IMSA’ s rules around engines for the Kelly American Challenge were pretty open. If it were a mass-produced engine under 366 cubic inches( 6-litre), you could use it. It didn’ t even have to match the manufacturer of the car. Where IMSA was strict was imposing minimum weights, and it tied that to engine capacity. Each car had to weigh 9.5lbs per cubic inch – 263kg for every litre, so a car with a 5-litre engine had to weigh 1315kg – and no car could weigh less than 2600lb( 1179kg). There was an exception for cars with big engines, a minimum weight of 3400lb( 1542kg) was capped for cars with 340 cubic inch( 5.5-litre) or larger motors. Cars were required to display their weight and engine displacement in 3-inch high letters on each side of the bonnet.
As in common practice, the IMSA race officials would measure the capacity of each engine by using a‘ Whistler’ device attached to an engine in place of a spark plug. Just one cylinder is usually checked, as it’ s assumed that the capacity of each cylinder will be the same.
Not in the case of Tommy Riggins’ Malibu. One cylinder, the one with the most easily accessible spark plug, had a smaller bore and so displaced less air than the others. It was this cylinder that the engine’ s capacity, and the car’ s minimum weight, were checked, calculated and displayed for all to see.
It was said that the cylinder on the opposite side of the engine was enlarged to make up for the difference in the small one. Very risky, if that was true, because if the officials had checked that cylinder, they’ d have found the engine to be bigger than its true capacity, and more weight would have been added.
At Road Atlanta in 1983, however, one of the IMSA tech inspectors chose neither of these cylinders to hook the whistler device up to. They chose one of the six equal-sized cylinders and found that the engine’ s total capacity was greater than previously calculated. That meant the size of the engine declared on the required bonnet stickers was wrong, and so was the car’ s minimum weight.
A conventional Chevrolet Small Block V8, with identically sized cylinder bores. Not like the block in Tommy Riggins’ Malibu
58 The Engine Rebuilder
Issue 05