Cummins 6BT

Cummins 6BT The Cummins 6BT is a 5.9 l (5,883 cc, 359 cu-in) six cylinders, four-stroke cycle water-cooled turbocharged internal combustion diesel engine, manufactured by American manufacturer Cummins from 1989 to 1998.

The 6BT engine has a cast-iron block with 102.0 mm (4.02 in) cylinder bores and a 120.0 mm (4.72 in) piston stroke. The compression ratio rating is 17.5:1. The motor has a cast iron cylinder head with a single camshaft (OHV) with two valves per cylinder; direct-injection design with a mechanical injection pump.

The Cummins 6BT 5.9 L 12v produced from 163 PS (120 kW; 160 HP) at 2,500 rpm to 218 PS (160 kW; 215 HP) at 2,600 rpm of maximum horsepower and from 542 N·m (55.3 kg·m, 400 ft·lb) at 1,600 rpm to 569 N·m (58 kg·m, 420 ft·lb) at 1,600 rpm of maximum torque.

General information

Engine Specifications
Engine code6BT
LayoutStraight-6, vertical
Fuel typeDiesel
Displacement5.9L, 5,883 cc (359 cu in)
Injection systemDirect-injection system (DI) with a mechanical injection pump
Power adder Holset H1C (1989-1993)
Holset WH1C (1994)
Holset HX35 (1994-1998)
Horsepower net From 163 PS (120 kW; 160 HP) at 2,500 rpm
to 218 PS (160 kW; 215 HP) at 2,600 rpm
Torque output From 542 N·m (55.3 kg·m, 400 ft·lb) at 1,600 rpm
to 569 N·m (58 kg·m, 420 ft·lb) at 1,600 rpm
Firing order1-5-3-6-2-4
Dimensions (L x H x W):
Weight498 kg (1,100 lbs)

Cylinder block

The cylinder block is made of cast iron. The crankshaft is supported by 7 bearings. Pistons are made of highly temperature-resistant aluminum alloy.

The cylinder bore is 102.0 mm (4.02 in), piston stroke is 120.0 mm (4.72 in) and the compression ratio rating is 17.5:1.

Cylinder block
Cylinder block alloyCast iron
Compression ratio:17.5:1
Cylinder bore:102.0 mm (4.02 in)
Piston stroke:120.0 mm (4.72 in)
Number of piston rings (compression / oil):2/1
Number of main bearings:7
Cylinder bore inner diameter:102.116 mm (4.0203 in)
Piston skirt diameter101.880-101.823 mm (4.011-4.0088 in)
Piston ring end gap:First0.400-0.700 mm (0.0157-0.0276 in)
Second0.250-0.550 mm (0.0098-0.0217 in)
Oil0.250-0.550 mm (0.0098-0.0217 in)
Piston pin outer diameter39.990 mm (1.5744 in)
Connecting rod small end diameter (standard):40.042 mm (1.5765 in)
Crankshaft main journal diameter:82.962 mm (3.2662 in)
Crankpin diameter:68.962 mm (2.715 in)

Main bearing cap tightening procedure and torque specs:

  • Step 1: 60 Nm; 6.0 kg·m; 45 ft·lb
  • Step 2: 119 Nm; 12.0 kg·m; 88 ft·lb
  • Step 3: 176 Nm; 18.0 kg·m; 129 ft·lb

After securing bearing cap bolts, make sure crankshaft turns smoothly by hand.

Connecting rod bearing bolts

  • Step 1: 35 Nm; 3.5 kg·m; 26 ft·lb
  • Step 2: 70 Nm; 7.0 kg·m; 51 ft·lb
  • Step 3: 100 Nm; 10.0 kg·m; 73 ft·lb

Flywheel fixing bolts

  • 137 Nm; 14.0 kg·m; 101 ft·lb

Cylinder head

Cylinder head
Cylinder head alloyCast-iron
Valve Arrangement:OHV, gear driven
Valves:12 (2 valves per cylinder)
Intake valve stem diameter:7.935-7.960 mm (0.3124-0.3134 in)
Exhaust valves stem diameter:7.935-7.960 mm (0.3124-0.3134 in)
Camshaft journal diameter (min):53.962 mm (2.1245 in)
Camshaft lobe diamete (intake)- min:47.040 mm (1.852 in)
Camshaft lobe diamete (exhaust) – min:46.770 mm (1.8413 in)

Head tightening procedure and torque specs:

  • Step 1: 90 Nm; 9.0 kg·m; 66 ft·lb
  • Step 2: 120 Nm; 12.0 kg·m; 89 ft·lb
  • Step 3: Turn all bolts 90°

Maintenance data

Valve clearance (Cold)
Intake valve0.25 mm (0.010 in)
Exhaust valve0.51 mm (0.020 in)
Oil system
Recommended engine oil10W-30 (CE or CE/SG)
Engine oil capacity With oil filter change: 9.5 L (10.04 US. qt, 8.36 Imp. qt.)

Vehicle applications

ModelYears Produced
Dodge Ram pickup1989–1998
Light duty, medium duty and select heavy duty trucks and buses
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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  1. On the Cummins 6 cylinder diesel: you stated a 12v engine. I can only assume that’s you meant a 2 valve head. I have seen 2 v. heads (so many), 3 valve heads (think Matchless/ AJS triple overhead cam), 4 valve heads (again so many, I believe Audi or BMW), then Honda 8 valve head. Yep. Sirochio Honda produced a 4 cylinder engine with 8 valves per cylinder, with double overhead cams, 8 rods for 4 pistons. I worked with a fellow that told me he had a DOHC engine in his car, quite a few years ago. He said, “Let’s go out and look at it.” He popped the hood open, and I said, “You don’t have a DOHC, you have a SOHC.” He insisted it was a DOHC because it had a cam for each bank of cylinders. I tried to tell him it doesn’t work that way. So, I am going to build an engine with 17 cylinders. No. 1 cylinder will have a Knight sleeve valve, #2 cylinder will have 1 valve per cylinder (think Detroit Diesel with 3 valves missing), #3 will have………. I think you might get the point. Cubic centimeters (ccm) are 1/9th of Centimeters Cubed (cm3). That is supposed to be cm with a 3 exponent. I can’t find a ‘character map’ on my tablet. Just for your perusal. Let me know your thoughts, Wayne


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