Written By, Mike McGlothlin
CAT 3116
History
CAT’s first real push into the small displacement “metric” engine market began with the CAT 3116. By metric, we mean that nearly all of its fasteners were of the metric variety and, to a lesser degree, that its displacement was listed in liters. The CAT 3116 engine features a 6.6L (402 cubic inch) displacement is derived from its 4.13-inch bore and its 5.00-inch stroke. A traditional cam-in-block, inline-six design, it featured a cast-iron block and a cast-iron, 2-valve per cylinder head. They made use of a single turbocharger, direct injection, and weighed in at approximately 1,500 pounds.
Common Applications
Not unlike other CAT engines, the 3116 was intended for global use across a myriad of industries. For on-highway use, it powered various buses, motorhomes, and GMC’s medium-duty TopKick trucks. Off-highway, the 3116 was widely used in marine applications, but also made its way into agricultural (row crop Challenger tractors), material handling (cranes and forklifts), industrial, power generation, and even military equipment (FMTV M1078). Power ratings for the CAT 3116 horsepower ranged from 170 hp up to as much as 355 hp in marine applications, with torque output spanning from 420 lb-ft to 735 lb-ft.
Production Run
The 3116 went into production in the early 1990s and was taken off the assembly line in 1998. But although its production run lasted less than a decade, the CAT 3116 set the stage for things to come. The engine’s same basic overall platform served as the basis for CAT’s small engine program that spanned from 1990-2010. Eventually, the 3116 became the 3126, which was followed by the 3126B, then the 3126E, the C7 and, finally, the C7S. Most 3116’s were equipped with Caterpillar’s mechanical unit injection system (MUI), but a small run in the late 1990s came with hydraulically actuated electronically controlled unit injection (HEUI). This evolution shows how early CAT 3116 specs influenced later generations.
How It’s Remembered
Depending on who you ask, the 3116 was either problematic or rock-solid reliable. Both are believable, and here’s a glimpse as to why. Their internal hard parts, especially within the short block (as well as the block itself), are highly robust. With proper care, the rotating assembly can be kept happy almost indefinitely. The problems with the 3116 are found on the top-end, where some highly involved maintenance is often required. Regular valve adjustments are necessary, and any disruption of the fuel injectors calls for special tooling in order to get the injector timing and synchronization with the internal rack just right. Despite the complex nature of the latter process, CAT’s 3116 is generally remembered favorably.
Sources:
Big Bear Engine Company
https://www.4btengines.com/cat-3116-engine/
Maintenance
https://mechanicshub.com/cat-3116-diesel-engine-memories/
Marine ratings
https://www.gulf-engines.com/wp-content/uploads/2015/03/CAT-3116-Engine-Specifications.pdf
