Written By, Mike McGlothlin
CAT 3066
History
It’s not the biggest inline-six in the Caterpillar arsenal, but the CAT 3066 engine has earned a well-deserved reputation for being a durable, consistent workhorse. Built by Mitsubishi Heavy Industries of Japan on behalf of CAT, the 3066 features a 4.02-inch bore, a 5.12-inch stroke, and displaces 389 cubic inches (6.4L). Par for the course for a dry sleeve, cast-iron block and head power plant in its respective segment (the head is actually a two-piece head, and uses two valves per cylinder). Weighing approximately 1,190 pounds, these core CAT 3066 engine specifications highlight its balanced design focused on durability, fuel efficiency, and reduced noise, vibration, and harshness.
Common Applications
CAT’s 3066 was available in various industries, but its primary calling lay in the construction sector, and notably Caterpillar excavators. It can also be found in material handling, mining, and agricultural equipment, as well as in power generation and a multitude of other industrial applications. Depending on configuration and equipment type, horsepower ratings range from 120 hp to just over 170 hp. Most versions produce peak torque at approximately 1,800 rpm, aligning with the conservative operating profile outlined in published CAT 3066 engine specifications.
Production Run
As a product of Mitsubishi Heavy Industries (MHI), Mitsubishi’s S6K and S6K-T engines are identical to the CAT 3066. Much like Perkins supplied smaller diesel platforms to Caterpillar, Mitsubishi provided mid-range engines and also built Caterpillar excavators for decades. The CAT 3066 engine Mitsubishi partnership represents a long-standing collaboration that combined Japanese manufacturing precision with Caterpillar’s global distribution and support network. This relationship contributed significantly to the engine’s long-term reliability and widespread adoption.
Why It’s Still Popular
The 3066 is extremely durable, offering a long service life despite the rigorous workloads most of them see. Because it typically sees low rpm, offering peak operation at 1,800 rpm or less, CAT’s 3066 doesn’t see the kind of wear-and-tear other engines in its class see. And with those low engine speeds comes fuel efficiency—something the 3066 is renowned for and that keeps the key operating cost involved in running a piece of equipment low. Add to that the fact that the engine is easy to service and parts are readily available and you begin to see why CAT’s 3066 is a heavy favorite among operators and equipment owners.
Contact Big Bear Engine Company today for more information on your CAT 3066 engine.
Sources:
Big Bear Engine Company
https://www.4btengines.com/cat-3066-engine/
3066 History
https://usedmachineryco.com/what-engine-is-in-a-cat-320c/
https://www.ruiqianfilter.com/info/caterpillar-3066-series-engine-power-and-reli-85190648.html
