Hot Rod Magazine Dynos Smokey Yunick’s 1963 Chevy 427 Mystery Motor

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Hot Rod Magazine Dynos Smokey Yunick's 1963 Chevy 427 Mystery Motor
Photo Credit: Hot Rod Magazine

Hot Rod Magazine recently celebrated the 50th anniversary of the big block Chevrolet Mark IV engine with a world-exclusive dyno test of one of the 427 Mystery Motors built by Smokey Yunick.

The 427 Mark II Mystery Motor isn’t actually part of the legendary Mark IV family, which debuted in 1965, but you can definitely consider it the missing link between the 348/409 and big-block Chevy engine families since it has characteristics from both.

Nobody knows exactly how many Mystery Motors were built before GM pulled the plug on factory-sponsored racing the day before qualifying at Daytona, but estimates range anywhere from 17 to 50.

Consequently, only a few of the Mystery Motors were ever handed out to racers Yunick, Ray Fox, and Rex White, who were allowed to keep the motors and finish out the season. Of course, without funding or factory technical support, their efforts were doomed. Nevertheless, the Mystery Motor that lurked under the hood of Junior Johnson’s Impala made the best of that short time, taking seven wins, nine pole positions, 13 top-5 finishes, and 14 top-10 finishes in only 33 races in 1963.

As the big-block Mark IV marks its 50th anniversary in 2015, Hot Rod recently had the privilege of dyno-ing one of the Rat Motor’s forefathers, a one-off Mystery Motor built by Yunick in the 1960s. The magazine called the experience “nerve wracking, historic, and a rush.”

Jim Dralle oversaw the operation, opening up the only existing race-version of a Mystery Motor that is now owned by Tom McIntyre. He pulled the valve covers, tuned the rocker assembly, pulled the oil pan to visually check the rotating assembly, and then closed it back up for a historic first run in 50 years on the Shaver Specialties dyno in Torrance, Calif.

Dralle found the engine to sound “tight and strong.” After letting it run for a few minutes, the valve lash and lifters were checked, and then the Mystery Motor was cranked again for pulls to 5000, 5500, and 6000 rpm, with horsepower still climbing at 440 but torque starting to drop after a high of 435 ft-lb at 5000 rpm.

Concludes Hot Rod: “McIntyre and Dralle were happy and relieved, while the HOT ROD staffers felt their elation, and considered the historical circumstances behind Chevy’s efforts to dominate NASCAR. Of course even before the 1963 Daytona 500 GM’s ban left Bow Tie believers forever to ponder what could have been.”


Source:
Hot Rod Magazine

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