Written By, Mike McGlothlin
CAT 3306
History
The word workhorse best describes Caterpillar’s 3306 engine. Released in 1973 (and widely debuting in excavators), the 638 cubic inch inline-six replaced the company’s outgoing 1673 and 3160 engine models. The CAT 3306 engine isn’t a powerhouse, but it is very robust and serves its purpose in ultra-reliable fashion. Thanks to its durability and versatility, CAT kept the 3306 on the production line for more than 20 years—dropping its yellow 10.5L power plant into all types of equipment along the way. The 3306 would prove to be the more reliable (and preferred) engine over the 3208, a parent bore V-8, and its longevity helped solidify enduring CAT 3306 specs in the heavy equipment market.
Common Applications
Off-highway or on-highway, the CAT 3306 is well-suited for a variety of applications and across all industries. In the construction world, it’s employed in everything from excavators to bulldozers to scrapers and motor graders to front-end loaders to rollers. Power generation, mining equipment, industrial pumps, and farm tractors also benefit from the platform. The marine industry has long relied on it as well, where CAT 3306 horsepower has powered trawlers, ferries, dredges, tugboats, drifters, and fireboats. On-highway use is less common, but the 3306 did see service in vocational and medium-duty trucks such as cement mixers and refuse trucks.
20+ Years In Production
Manufactured until 1995 in the states (and as far as 2004 for global applications), Cat’s 3306 represents the type of lengthy production run that wasn’t unheard of back in the day. The late 1970s, 1980s and early 1990s were the golden age for diesel engines. Mechanical injection was the norm and electronics weren’t yet a necessity. The major emission regulations crunch hadn’t occurred yet and engines weren’t saddled with the durability-killing exhaust aftertreatment technology that exists today. At of the end of 2024, Cat reported 2.1 million engines operating in active construction machines all across the globe. You can bet many of them were old-school 3306’s.
Why It’s Still Viable Today
In another word: durable. CAT’s 3306 is graced with big bearing surfaces, a robust, cast-iron block with wet liners, and a beefy, cast-iron head with six bolts per cylinder. And with an overhead valve (OHV), 2-valve per cylinder design and no electronics to speak of, it’s also stone-age simplistic. With proper maintenance, a 3306 can last for decades, and many of them have chugged along for 30 years before requiring an overhaul. Whether it’s being used in a gen-set, industrial pump, construction equipment or a boat, it’s much more cost-effective to rebuild an old 3306 than “upgrade” to a modern diesel power plant, especially one weighted down with all the (expensive) exhaust aftertreatment devices that always seem to have a way of shortening the service life of the engine.
Sources:
Big Bear Engine Company
https://www.4btengines.com/new-engines/cat-3306/
Caterpillar
https://www.caterpillar.com/en/company/working-together/caterpillar-at-a-glance.html
Introduction To The CAT 3306 Engine
https://www.youtube.com/watch?app=desktop&v=nTgy6KXpBP8
KMP Brand
https://www.kmpbrand.com/kmp-insider/the-history-of-caterpillar/
