Caterpillar 3412

The Caterpillar 3412 is a heavy-duty industrial diesel engine from Caterpillar's 3400 series, sitting at the top of that family's V-configuration lineup alongside the smaller inline-six 3406 and V-8 3408. It is a 65-degree V-12, four-stroke-cycle diesel displacing roughly 27.0 L (about 1,650 cu in), with a 137.2 mm x 152.4 mm (5.40 in x 6.00 in) bore and stroke, wet cylinder liners, and four valves per cylinder. Caterpillar built the base mechanically-injected engine from around 1979 into the 1980s and 1990s, then carried the platform forward as the 3412C (mechanical injection with electronic governing) and, from 1996, the HEUI-electronic 3412E, before the displacement class transitioned to the C27/C30 engines. Cat offered the 3412 naturally aspirated, single-turbocharged, sequential-turbocharged, and turbocharged-aftercooled (DITA), spanning roughly 373-1,050+ kW (500-1,450 hp) depending on generation and duty cycle - varies by configuration/series. A bare industrial-rated engine weighs on the order of 2,730 kg (about 6,020 lb) dry; marine propulsion/auxiliary builds run somewhat lighter, and packaged generator sets weigh considerably more once the alternator, radiator, skid, and enclosure are added. Typical uses span generator sets, pump and compressor drives, well-service and drilling power units, marine propulsion and auxiliary power, and off-highway trucks.

Across its production life the 3412 moved through three broad control generations: the original mechanically-governed engine with jerk-type unit injection, the 3412C which kept mechanical injection but added electronic governing for tighter fuel and speed control, and the 3412E, introduced in 1996, which switched to Caterpillar's HEUI (hydraulic electronic unit injection) system for variable injection timing, quicker load response, and higher rated outputs. As emissions rules tightened further, Caterpillar migrated this displacement class into the mechanically-simpler C27 and the electronically controlled, higher-output C30, and in the large medium-speed marine/industrial niche the 3412 itself had commonly replaced Caterpillar's earlier D398 V-12 in repower projects. Because the 3412 family was built for two decades-plus in very large numbers across marine, power-generation, and oilfield markets, it remains one of the most common heavy-bore V-12 diesels in the used-equipment and rebuild market today: values reward mechanical simplicity and field-serviceability (particularly on pre-E units), aftermarket rebuild-kit and parts support is strong, and well-maintained units are routinely documented running 25-40 years and toward 10,000 hours between overhauls - which keeps the platform in active repower, standby-power, and industrial pump-drive service long after new-unit production ended.

Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.