“I always thought that engine was tuned to the horsepower number,” says McCarthy, meaning that to reach the 425-hp benchmark engineers tuned the engine for revs to the detriment of usable torque. McCarthy & his team settled on giving the big-block a 0.9-mm increase in bore to 103.9 also a 3.6-mm stretch to the stroke to 94.5, for a total of 6410 cc.
The whole 392 thing was a total coincidence. So says Dodge Challenger chief engineer Tom McCarthy. In 2009, McCarthy & his team were discussing a punch-out of the Challenger SRT8’s peaky 6.1-liter V-8 for more midrange torque.