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Cat 3304 Engine

CAT 3304 Engines For Sale

3304 Cat Engine on Top of a Wooden PlatformCaterpillar's 3304 Engine is a naturally aspirated, in-line four-cylinder, four-stroke engine that is capable of 95 hp at 100% power, and 71 hp when its workload is reduced to 75 percent. The Caterpillar 3304 engine was released in 2009 and is classified as a heavy-duty industrial engine that operates on natural gas as opposed to diesel fuel. Cat claims the 3304 has a track record for reliability, along with a capability to burn a wide spectrum of gaseous fuels, which the company says prolongs the engine's life while simultaneously lowering its operating costs.

Engine Applications

  • Industrial Use

Common CAT 3304 Engine Problems & Failures

At Big Bear Engine Company, we see certain pattern problems that often lead to customers being forced to replace their 3304 engines. So, to put this to good use, we’ve compiled a list of the most common problems we encounter. Some of the issues below may mean your engine has run out of time. However, under other circumstances certain parts can be salvageable if the engine failure is caught in time.

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  • Spun Crankshaft Bearings
  • Cracked Cylinder Head
  • Camshaft Failure
  • Connecting Rod Failure
  • Crankshaft Failure
  • Dropped Valves
  • Extreme Blow By
  • Lack of Oil Pressure (or no oil pressure)
  • Lifter/Roller Failure
  • Overfueling
  • Scored Pistons and Liners

CAT 3304 Engine Replacement Options

There are a host of issues than can harm your engine, but not all of them mean your engine is dead in the water. While certain failures mean the engine is beyond saving, at times, some 3304 Cat engines simply need a few replacement parts, or a refresh. We understand that factors like time, money, and availability will factor into your decision when it comes to purchasing a new engine. This is exactly why we provide long block engine options.

Replacement Option Chart of 3304 Cat Engine

Remanufacturing Process

For anyone reading this that has had the misfortune of losing an engine, our remanufactured 3304 Cat long blocks are a sound solution. Moreover, if you have good, re-usable external components we will inform you that these can be salvaged from your original Caterpillar 3304 engine and be transferred onto the new one. Most importantly, Big Bear 3304 Cat long block is a great options if you're trying to work on a budget.

We’re a company that’s renowned for always upholding a professional level of service, whatever the task. In the sphere of engine remanufacturing, we ensure this level of quality is upheld by first executing a full core tear down, followed by comprehensive cleaning, inspection, and machining of your CAT 3304 engine. This extensive quality control process is carried out on every engine we build.

It’s crucial to note that all of our Caterpillar 3304 remanufactured long blocks are built with both reman and new parts. We do not just recondition or refurbish old parts. Instead, we completely rebuild your old 3406 Cat back to its original OEM specs.

Comprehensive Cleaning

A thorough cleaning is essential in the engine rebuilding process; Our goal is to spot any impurities or potential structural flaws that could contribute or cause both component failure or engine failure. This is performed by stripping the 3406 Cat engine and then putting the block, head, rods, crankshaft, and camshaft through a chemical jet wash or hot tank.


Before our quality control division inspects the finished product, each crankshaft is precision machined to the exact tolerances, polished and then magnafluxed.

Cylinder Head

Each head is resurfaced to guarantee a proper sealing surface with the block and head to provide a finish compatible with today's new head gasket materials. Valve height is also mic'd, and every head is vacuum-tested to assure correct valve seating.


Magnetic particle inspection is a common practice for any reputable engine builder, and we magnaflux each crankcase to check for any cracks or damage. The cylinders are then bored, honed and inspected once again. Torque plate honing is also performed on particular engines in order to eliminate the chances of cylinder distortion when the head is bolted and torqued to the block. This process subsequently removes the main source of engine blow-by. Block surfaces are then machined and inspected to ensure a proper finish.


The camshaft is inspected and precisely machined to provide correct lift. Lobes are measured with a micrometer to ensure OEM tolerances are met.

Connecting Rods

Each connecting rod is carefully analyzed for signs of bend and/or twist. In order to achieve an even distribution of stress across the bearings, the connecting rods are cleaned and machined to OEM specs before being honed to the traditional diameter of the original equipment. New bushings are also installed and machined in all bushed rods.

New Parts

Great performance and reliability are what we strive for at Big Bear Engine Company. This is why all of our CAT 3304 engines feature fresh pistons and rings, bearings, gaskets, and seals. The new parts are made up of a combination of both OEM and aftermarket components, when accessible.

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Please fill out the form below with your information and request. A member of our staff will be with you shortly.

Remanufactured Engines Standards

To best define the term remanufacture, would be to "make as close to new as possible." In pursuit of this, all wearable parts are routinely replaced. All 3304 Cat engine's core materials are then carefully inspected and examined against the original equipment specifications for correct dimensional tolerances. Every replacement part is new or requalified. If new, parts are made using the same production methods as the original equipment. Finally, testing is performed to manufacturer specifications and original production standards.

CAT 3304 Long Block Parts List:

  • Block
  • Cylinder Head (Complete and Loaded)
  • Intermediate Cover
  • Timed Front Gear Group
  • Pistons
  • New Upper and Lower Gasket Set
  • Camshaft
  • Followers/Lifters
  • Liners
  • Rings
  • Crankshaft
  • Connecting Rods
  • **1 Year Warranty

*Note: Big Bear Engine Company can provide a new oil pump, oil cooler, water pump, injector and fuel pump for additional cost with the long block, but these parts will not come assembled to the engine.

**First 6 Months Parts & Labor, Second 6 Months Parts Replacement Only. Ask your sales representative for a full copy of our remanufactured long block warranty.

CAT 3304 Specs

Engine Data

Min Power71 hp
Max Power95 hp
Rated Speed1,800 rpm
Bore4.750-inches (121 mm)
Stroke6.000-inches (152 mm)
Displacement7.0 L
Engine ConfigurationContinuous
AspirationNaturally Aspirated
Length45.6 in
Width29.28 in
Height46.11 in
Weight Net (dry)1,670 lbs

Give us a call today at 844-340-4114 for immediate sales and support for the Cummins 4BT, Cummins 6BT, 6CT, ISC, 855, QSB 4.5 L or CAT 3306. If you have any questions, check out our FAQ Page. We are always ready to help or just listen to your crazy off-roading adventures!

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