The 71-series engines are huge, whether they're inline or V-type. What the name stands for is "71 cubic inches per cylinder", so a 6V-71 is a 426 cubic inch engine that fires on every upstroke of the piston because it's a 2-cycle. It would have the same number of power impulses per mile as an 852 cubic inch 4-stroke. That's why the older Detroit engines sound like they're running so fast- - - - -they're making as much noise as a 4-stroke running twice the RPM.
A 53-series engine has 53 cubic inches per cylinder, so it's smaller and lighter. They're much more suitable for medium-duty truck use, but they're still big, heavy, and noisy. The term "screamin' Jimmy" is well-deserved, especially when the howl of the blower gets factored into the equation.
Jerry
