WHAT MAKES THE CUMMINS SO GREAT

…AND THE AFTERMARKET PARTS THAT MAKE IT EVEN BETTER

- MIKE MCGLOTHLIN

The Cummins. It’s the engine that brought inline-six architecture, direct injection, the P-pump, and true, industrial-level strength to the ¾-ton truck market. In either 5.9L or 6.7L form, its stroke (4.72-inch, and then 4.88-inch) dwarfs the competition and as such produces the most usable off-idle torque of any engine in the segment. Higher in the rev range, it’s always been able to hold its own in the horsepower department as well. Not surprisingly, the majority of all aftermarket endeavors are geared toward the ’89-present 5.9L and 6.7L Cummins mills.

But why was the Cummins so overbuilt? For starters, it was originally intended for off-highway, round-the-clock use. At the outset, it was designed to power tractors, wheel loaders, mobile cranes, and gen-sets—with production of the 6BT starting as early as 1983. With Cummins looking to score an even larger contract than the one it landed with Case, Chrysler—which happened to be shopping for a diesel engine to power its 250 and 350 series Dodge trucks—came along at the perfect time. Equivalent to hitting the jackpot, the Cummins option revived the automaker’s dying truck line while also redefining everything a heavy-duty pickup could be.

Starting with its iron foundation and then moving on to the burly parts that reside within it, in the following pages we’ll explore why the Cummins is so robust and how you can make yours even better.

The 6BT 5.9L Cummins unquestionably revolutionized the diesel option in the pickup truck market when it debuted in ’89 model year Rams. However, plans for the Cummins/Case joint venture engine were on the drawing board long before that, with engines destined for Case off-highway equipment in production by 1983. Believe it or not, the 4BT (its four-cylinder cousin) went into production prior to the six-cylinder.