Cummins 4BT specs at a glance

The table below deliberately keeps each published Cummins configuration in its own column. A blank cell means the cited product page does not publish that value; it does not mean the value is zero or unknown to Cummins.

For a practical comparison with the six-cylinder platform, see our Cummins 4BT vs 6BT specs and size guide. It explains the platform-level differences without treating every rating as interchangeable.

Why horsepower and torque require a complete build identity

Displacement alone does not establish output. Cummins publishes different power bands for different 3.9-liter products, and the rating changes with fuel system, air handling, calibration, duty cycle, market and emissions package. Even the marine page distinguishes intermittent and high-output terminology. A seller who says every 4BT produces one fixed horsepower number is omitting the configuration that makes the number meaningful.

Torque must be treated the same way. Do not infer a torque value from displacement or from another engine that looks similar. Record the rated power, rated speed and duty statement from the dataplate or an ESN-specific Cummins record. If a data plate is damaged, use Cummins QuickServe or an authorized service channel to recover the correct build information before specifying fuel or air-system components.

Weight and dimensions: use envelope data, not a universal number

The 360 kg and 707 x 772 x 793 mm figures above are useful because Cummins publishes them for the named ReCon 4BT marine package. The 338-355 kg wet range and 777 x 625 x 958 mm dimensions belong to the cited B3.9 Tier 2 product. They are not conflicting measurements; they describe different arrangements and measurement conditions.

Installed size can change with the flywheel housing, fan, starter, alternator, cooling package, mounts, exhaust orientation, air cleaner, gearbox or marine gear. Published product guides also warn that dimensions may vary by configuration. For an engine swap or repower, measure the actual package and confirm service clearances, lifting points, center of gravity, accessory removal space and driveline alignment. A catalog envelope is a screening tool, not a fabrication drawing.

Oil and coolant capacity are build-specific

Oil capacity changes with the oil pan, dipstick calibration, filter arrangement and installation angle. Coolant capacity changes with the engine water jacket plus radiator, hoses, heat exchanger and other external circuit volume. The B3.9 Tier 2 page publishes 10.9 L for its oil system, but applying that number to every 4BT would be unsafe.

Use the ESN-specific operation and maintenance manual. After service, follow the specified fill and run procedure, check for leaks, allow the oil to drain back, and verify the level using the correctly calibrated dipstick. For coolant, identify the complete installed system and the approved coolant specification rather than relying on an engine-only estimate.

How to identify a Cummins 4BT correctly

Start with the complete engine dataplate. Photograph the entire plate in good light and record every line, including the engine serial number, model designation, CPL, rated output, rated speed and any family or emissions information. Do not crop away prefixes, suffixes or leading zeros. Those characters may separate otherwise similar builds.

Dataplate and stamped-number locations can vary with engine arrangement and installation. Avoid assuming one universal location from a web photo. Cummins directs owners to QuickServe and its manuals resources for ESN-based service and parts information. If the plate is missing or unreadable, document the block casting, head casting, fuel pump identification, turbocharger tag, flywheel housing, oil pan, piston features and the machine or vessel application. Then ask a qualified supplier or Cummins channel to reconcile the evidence.

Our illustrated Cummins 4BT and 6BT identification guide shows the evidence to collect before requesting a quotation.

1. Photograph the full dataplate and record the ESN and CPL exactly.
2. Record the model, rating, rated rpm, application and equipment serial number.
3. Photograph casting numbers and component tags without assuming they are the engine ESN.
4. Note aspiration, fuel-system type, oil-pan shape, flywheel housing and accessory layout.
5. For overhaul parts, measure the removed components and record any oversize or undersize markings.

Verified application context

Cummins currently describes the ReCon 4BT page as a marine propulsion product. Its published output and package measurements should therefore be read in that marine context. Cummins lists construction and compressor applications on the cited India-market 4B3.9 industrial page. These manufacturer statements verify that the 3.9-liter platform appears in more than one duty environment, but they do not prove that a part from one build fits another.

When buying for a generator, vehicle, pump, compressor, machine or vessel, include the original equipment manufacturer, equipment model and serial number. The equipment maker may specify a unique front-end drive, sump, cooling arrangement, governor setting or housing even when the base engine family is familiar.

Parts groups and what to verify

A full overhaul request often begins with a 4BT overhaul kit, but the kit description is only the start. Use our Cummins 4BT rebuild kit buying guide to build a measured checklist before ordering.

• Cylinder block and rotating group: verify bore condition, piston design, pin size, ring arrangement and any machining. Compare the removed piston before selecting a 4BT piston listing or 4BT3.9 piston-ring listing.
• Crankshaft and bearings: measure every journal and confirm standard, oversize or undersize requirements. Review the measured result before choosing a 4BT standard main-bearing listing. Check crankshaft end play and the removed profile before selecting 4BT thrust washers.
• Cylinder head: record the head casting, valve arrangement, injector bore and installed hardware. Compare those details before reviewing a 4BT cylinder-head listing.
• Valvetrain: measure stems, guides and seats; verify intake and exhaust positions. Use the evidence before selecting 4BT valve seats or a 4BT engine-valve listing.

Product pages above were live and ACTIVE when this guide was checked. A live listing is not an automatic fitment guarantee. Compatibility must still be confirmed from ESN/CPL data, original part numbers, casting marks and physical measurements.

Ordering checklist for a reliable quotation

1. Send clear photos of the full engine dataplate, ESN, CPL and equipment plate.
2. State the application, duty, rated power and rated speed.
3. List the exact parts required and the original numbers found on boxes or removed components.
4. Provide cylinder bore, crank journal measurements and repair-size markings after inspection.
5. Photograph piston crowns and bowls, rings, bearings, head casting, valves, guides and seats.
6. Identify the fuel pump, injectors, turbocharger and cooling arrangement if related parts are needed.
7. Confirm whether the engine is being rebuilt to its original specification or has documented prior changes.
8. Ask the supplier to state what evidence was used for the match and which items still require measurement.

Frequently asked questions

What is the displacement of a Cummins 4BT?

Cummins publishes 3.9 L, or 239 cubic inches, for the named ReCon 4BT marine product. Other 4B3.9 pages also identify the 3.9-liter family, but ratings and installation data remain configuration-specific.

How much does a Cummins 4BT weigh?

There is no single safe universal weight. Cummins lists 360 kg (794 lb) for its named ReCon 4BT marine package and 338-355 kg (745-782 lb) wet for the cited B3.9 Tier 2 product. Confirm the exact build and installed accessories.

What are the dimensions of a Cummins 4BT?

Cummins lists 707 x 772 x 793 mm for the named ReCon 4BT marine package. The cited B3.9 Tier 2 page lists 777 x 625 x 958 mm. Configuration, accessories and measurement conditions can change the envelope.

Where is the Cummins 4BT engine serial number?

Location can vary by arrangement and installation. Inspect the complete engine dataplate first and use Cummins QuickServe or the appropriate manual. If it is unreadable, document casting marks and component tags for expert identification instead of guessing.

Are all Cummins 4BT parts interchangeable?

No. Shared family names do not prove interchangeability. Verify ESN, CPL, original part number, casting, piston and ring design, repair size, fuel system, application and measured dimensions before ordering.

Official sources

• Cummins ReCon 4BT product page
• Cummins 4B3.9 industrial product page
• Cummins B Series Tier 2 product page
• Cummins QuickServe Online
• Cummins manuals and technical documents
• Cummins Marine Products Guide