5.9L Cummins 6BT (12 Valve)

The venerable 6BT Cummins was introduced in 1984 for various agricultural equipment applications by Case. Fast forward to 1989, Chrysler partnered with Cummins to offer the 5.9L Turbodiesel in their 3/4 and 1 ton Dodge pickups. The 12v Cummins quickly became a popular alternative to Dodge's V-8 gas engines, as the diesel generated nearly double the torque at low engine speeds and provided a significant increase in fuel economy, particularly while towing. The 12v Cummins, or 6BT, received an intercooler for the 1991 model year and the P1700 injection pump replaced the VE for the 1994 model year. The 12v Cummins is arguably the most popular of the various engine platforms that would follow as its simplistic nature and respectable performance characteristics are highly desirable. The 6BT was the first, and Dodge remains the only engine manufacturer to offer an inline 6 diesel in the pickup truck segment.

5.9L Cummins 12v Specs, History, & Information

Cummins produced the 5.9L 12v Cummins for Ram pickup applications through the 1998 model year, where it was phased out in favor of a more emissions friendly 24 valve platform. The engine's widespread applications include light and medium duty trucks, agricultural equipment, and construction machinery. A long stroke and undersquare bore-to-stroke ratio yield favorable low end performance, producing peak torque at a meager 1,600 rpm. Although the 6BT tips the scales at a hefty 1,100 lbs, its burly cast iron block and cylinder head contributes to the engine's superior reputation with regard to reliability and longevity. Additionally, its inline configuration eases service and repair efforts by providing generous amounts of workspace on either side of the engine block without the spacial restrains inherent of V-8 arrangements.

12v Cummins Heater Grid Cycle Schedule

In place of a traditional glow plug system, the 6BT Cummins relies on a heater grid (single resistive heating element) mounted between the air horn and intake manifold to assist with cold starting. Cummins engines are well known for starting quickly and with minimal effort, despite the fact that the heater grid is only designed to cycle when the ambient temperature drops below 59° F.

Intake Air Temperature

Pre-Heat Cycle Time

Post-Heat Cycle

> 59° F

no pre-heat cycle

no post-heat cycle

59° F to 15° F

~ 10 sec


15° F to 0° F

~ 15 sec


< 0° F

~ 30 sec


Killer Dowel Pin Concerns (KDP)

No engine is without inherent faults, and the 12v Cummins Achilles heel is a small dowel pin pressed into the front of the engine during assembly to enable proper alignment of the front cover (timing cover). Technicians and shade tree mechanics alike have come to coin this the "killer dowel pin", or KDP for short. The small dowel is amply named because, should it dislodge, there is a fair chance that the pin will bind between a series of timing gears behind the front cover and cause significant, if not catastrophic damage.

Engine vibration is the culprit behind dowel pin dislodging events, which can cause catastrophic, irreparable damage should the pin attempt to mesh between any two of the series of gears located behind the front cover. Alternatively, the dowel pin could deflect off the rapidly moving gear train and land peacefully in the basin of the front cover assembly without causing any damage whatsoever.

Preventing dowel pin related engine failures is as simple as removing the front engine cover and installing a KDP tab or KDP eliminator kit that completely and permanently restrains the dowel pin within its bore in the engine block. Because the danger is so prevalent and prevention is not overly cumbersome, 12v Cummins owners are typically urged by industry experts to install a KDP eliminator kit as it is inexpensive insurance against possible (and preventable) engine damage. KDP tabs are generally available for a few dollars while complete kits, which include the required crankshaft seal, gasket/sealant, and associated hardware can be acquired in the $60 to $120 range depending on the type of kit. For more information on KDP eliminator kits, see: 12v Cummins KDP Tab Installation. For details on our recommended installation kit, see: 12v Cummins KDP Tab & Installation kit

12v Cummins Transmission Options (Dodge Ram Applications)

The 12 valve Cummins was offered behind a number of transmissions during its service life, which include the Chrysler 47RH (4 speed automatic), GETRAG G360 (5 speed manual), and New Venture NV4500 (5 speed manual). Of all transmissions offered, the NV4500 5 speed manual transmission is by far the most popular and desirable transmission option. The transmission suffers from 5th gear failure, however this is easily repaired and even preventable. The transmission's reputation is otherwise sound and its ratio spread provides a comfortable driving experience in loaded and unladen driving conditions.

5.9L Cummins 12v (6BT) Engine Specs


Cummins 6BT (commonly referred to as the "12 valve Cummins")


Cummins Engine Company

Applications/Production Years:

1989 - 1993 Dodge W250, W350, D250, D350 pickups
1994 - 1998 Dodge Ram 2500/3500 pickups
Various industrial, agricultural, and motorhome applications of similar period


359.02 CID (359 CID nominal), 5.88 liters (5.9 liters nominal)


Inline 6 cylinder (I-6), 4 cycle diesel

B10 Life:

Not rated

B50 Life:

350,000 miles (~560,000 km)


4.02 in (102 mm)


4.72 in (120 mm)

Bore/Stroke Ratio:

0.85 (undersquare)

Compression Ratio:

17.0 : 1

Firing Order:


Cummins diesel cylinder numbers

Engine Block Material:

Cast iron

Cylinder Head Material:

Cast iron

Injection System:

Direct injection (DI), mechanical gear driven injection pump, mechanical fuel injectors

1989 - 1993

Bosch VE44 rotary injection pump

1994 - 1998

Bosch P7100 inline injection pump


1989 - 1991

Holset H1C turbocharger, non-intercooled

Mid 1991 - 1993

Holset H1C turbocharger, air-to-air intercooler


Holset WH1C turbocharger, air-to-air intercooler (note - 1994 engines will either use a WH1C or HX35)

1994 - 1998

Holset HX35 turbocharger, air-to-air intercooler


OHV, 2 valves per cylinder (12v), solid lifter camshaft

Valve Lash (Clearance):

Exhaust valves

0.020" (engine cold)

Intake valves

0.010" (engine cold)

Electrical System:

12 volt

Cold Start Aid(s):

Intake air grid heater mounted between air horn and intake manifold

Engine Oil Capacity:

12 qts w/ filter (Dodge pickup applications, may vary in industrial/agricultural applications)

Engine Oil Spec:

See 12v Cummins maintenance schedule for engine oil viscosity chart


#1/#2 diesel fuel; engine predates modern biodiesel availability[1]


160 - 215 HP @ 2,500 RPM


400 - 440 lb-ft @ 1,600 RPM

Governed Speed:

~ 2,700 RPM

Engine Weight:

~ 1,100 lbs, dry & dressed (~ 890 lbs dry, engine assembly only)

Engine Dimensions:







[1] - The 6BT Cummins predates modern ULSD regulations and biodiesel compatibility. The engine will run without issue on both fuels, although the effects of extended biodiesel usage are largely sporadic, vague, and/or unknown. Recommend a supplemental fuel additive to increase fuel lubricity regardless of diesel fuel type used, which will help prolong fuel system life.

5.9L Cummins 12v (6BT) Horsepower & Torque by Model Year (Dodge Applications)

Model Year



1989 - 1993

160 hp @ 2,500 rpm

400 lb-ft @ 1,600 rpm

1994 - 1995

• 160 hp @ 2,500 rpm (auto trans)
• 175 hp @ 2,600 rpm (manual trans)

• 400 lb-ft @ 1,500 rpm (auto trans)
• 420 lb-ft @ 1,500 rpm (manual trans)

1996 - 1998

• 180 hp @ 2,500 rpm (auto trans)
• 215 hp @ 2,600 rpm (manual trans)

• 420 lb-ft @ 1,500 rpm (auto trans)
• 440 lb-ft @ 1,500 rpm (manual trans)

12v Cummins horsepower and torque chart by model year for Dodge trucks

5.9L Cummins 12v (6BT) horsepower & torque by model year (1989 - 1998 Dodge trucks)