A document containing official horsepower and torque numbers for GM’s brand new 6.6-liter V8 Duramax turbo-diesel was found buried on the GM Powertrain website – before the company quickly deleted it.

The next-generation turbo-diesel 6.6-liter Duramax engine, set to debut in the 2017 Chevrolet Silverado heavy-duty and GMC Sierra heavy-duty pickup trucks, will offer more torque, power and fewer ...