Courtesy of Engine Builder by Evan Laux
3.0 Limited Pro Stock engines are high-performance diesel engines used in truck pulling competitions. These engines are designed to produce massive amounts of power and torque, allowing the truck to pull heavy loads over a short distance.
The 3.0 Limited Pro Stock engine is typically based on a standard 6.7L or 5.9L Cummins diesel engine block, although Duramax engines are also used. The engine block is often sleeved with stronger materials and the crankshaft is also usually upgraded for increased strength; other heavily modified components are tacked on to increase performance even further. The 3.0 Limited Pro Stock engine is also equipped with high-performance pistons, heavy-duty connecting rods, and a custom camshaft. These components are designed to withstand the high stresses generated by the engine’s power output.
Dustin Harrison, owner of Apex Diesel Performance, is versed in building engines for this class. His Atlantic, PA shop opened its doors in 2014 and they’ve been completing quality, performance Cummins engine builds ever since. We first spoke with Harrison in late 2019, where he told us all about a Super Stock 6.7L Cummins he was building at the time.
The Limited Pro Stock engine he just finished for competitor Trent Krulik will have less horsepower on hand than that Super Stock Cummins build, but that doesn’t make it any less impressive.
“They’re about half the power of a Super Stock, but it’s an interesting class since there’s so many restrictions on how you make power,” Harrison says. “They’re air-limited, so they’re restricted to a 3-inch smooth bore inlet on the turbo, and you can’t have water injection. So, all we have is a 76mm turbo on there and it’s making close to 1,600 horsepower, which is quite a bit for a small, single-turbo application.”