Caterpillar G353D

The G353D is Caterpillar's industrial spark-ignition natural gas engine from the company's older big-bore "300 series" gas engine line, alongside the G342, G379, G398, and G399, sharing bottom-end architecture with the D353 diesel block (inline six-cylinder, roughly 24.2 liter/1,473 cu in displacement). It is carbureted, magneto-fired, and governed by a mechanical flyball governor, with no electronic engine controls. Base naturally aspirated units are rated around 270 hp (~201 kW) at 1200 rpm; a turbocharged-and-aftercooled version was also offered. Caterpillar built the G353D under serial prefix 64B (64B00001-up) starting in the early 1960s, before its emissions-era gas engine families existed. It was sold as a bare power unit, not a complete machine: no factory undercarriage, hydraulics, or transmission, driving external equipment such as generator sets, gas compressors, pumps, and marine or industrial drives instead. No factory weight or dimension figures are publicly documented for this engine, since installed weight varied with the flywheel housing, cooling arrangement, and driven equipment coupling. Buyers specified the block to the application, choosing from multiple cooling arrangements (standard radiator, high-capacity radiator, remote/surge-tank, or ebullient steam-cooling), 32V electric or air starting, an enclosed flywheel clutch/PTO, and an auxiliary generator/charging arrangement.

Across its production run Caterpillar revised the G353D's crankshaft and main-bearing hardware at least twice, marked by internal serial sub-breaks around 64B312 and again near 64B520; later-built units use updated bearing components, so parts and clearances need to be checked against the actual serial number rather than the model tag alone. As a pre-emissions mechanically governed design with no diagnostic electronics, the G353D needs no emissions compliance and keeps running on gauges and mechanical shutdown switches, which still makes it a viable low-cost option for replacing worn-out gensets, compressors, or pump drives where electronic engine controls aren't required or wanted. It's also obscure enough today that dedicated documentation is thin: parts sourcing increasingly relies on cross-reference to the shared D353 diesel block and the related G379/G398/G399 gas-engine castings rather than G353D-specific stock. That makes surviving units and remaining spares a niche but real market, traded mostly among industrial gas-engine rebuilders and specialists who understand the family's shared architecture and serial-based bearing generations.

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.