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Engine Swap, Ask Anything - February 2013

Reverse Rotation Engine for Derby
Robert Stiles; Greendale, IN: I am building a reverse rotation engine for a local demolition derby. It is well known that derby cars are in reverse most of the time to save the radiator. I would like to have my engine turn counter-clockwise (backward) so I can utilize all three gears in my tranny as reverse, and reverse as a low gear to drive forward. Is this possible?

Jeff Smith: Wouldn't it just be easier to relocate the radiator to a safer location than to convert to a reverse rotation engine? Maybe it's not legal per the rules. Are there rules in demo derby? But your question piqued my interest in what it would take to make a reverse rotation engine. Let's use a small-block Chevy as our example. At first, it seems all you would have to do is to have a cam company grind a reverse-rotation camshaft. But then that would reverse the rotation of the distributor gear, which might change gear wear. It would also mean the standard mechanical and vacuum advance would not work, so you'd have to convert to electronic ignition control. Next, the oil pump will not pump if turned in reverse, which means you'd have to convert to an externally driven oil pump with the requisite plumbing. At least the water pump would be easy since serpentine belt engines all use a reverse-rotation water pump. But if you ran this pump with a serpentine belt, the pump would be running in the “correct” rotation and would be running backward. So you would need to convert that pump to run with a non-reverse beltdrive. Finally, a stock starter motor would spin the engine in the wrong rotation, so you would need a reverse-rotation starter motor. You can't move the starter to the other side of block because it would hit the oil-filter boss. Next, the trans is also going to spin in reverse, which might mean that the pump may not make pressure. I'm probably missing a couple items here, but as you can see, a reverse rotation engine isn't really a good idea mainly because you'd probably have $3,000 or more invested in a demolition-derby engine, and I doubt winnings would pay you back. I think you'd be better off to just put the radiator on the roof of the car with an electric fan.

Smokey Yunick built a reverse rotation Offy engine for the '59 Indy 500. The reasoning behind his approach was that by reversing the engine's rotation, the torque reaction in the chassis would push the right-rear tire into the pavement in the middle of the corner as engine torque increased on corner exit. According to Smokey's book, the car was a rocket coming off the corners because he could apply power off the corner sooner than the other cars. I stumbled across a reverse rotation small block Chevy that he built, which has now taken up residence at the Speedway Motors museum in Omaha, Nebraska.

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Speedway Motors

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