We first told you about the amazing supercharged intercooled 6.2-liter LS9 engine in the 2009 Corvette ZR1 back in the April 2008 issue (“King Of The Hill”). Since then, one of our readers, Doug Cooper of Syosset, NY, has taken delivery of a black ZR1. You may remember Doug from the feature we ran on his big-block—powered ’55 Chevy 210 (“Hidden In Plain Sight,” March 2008). That Chevy had a 700hp 540-ci Rat motor—which is plenty powerful for most, except for the 3,800-plus pounds of mass. Doug’s ZR1 weighs 500 pounds less, and makes 620 hp at the flywheel, making it more nimble than his ’55. So what does the ZR1 put to the ground after passing through a beefy six-speed manual transaxle? Doug took his ZR1 down to The Vette Doctors (Amityville, NY), where it cranked out 549.9 rear wheel hp at 6,600 rpm on their Dynojet. That makes the ZR1 drivetrain either extremely efficient beyond belief, or the factory rating of 620 hp is very conservative.