Ram Tough Rebuild - Cummins Engine Specs
By Roy Berndt
The B-series Cummins engine may potentially go down in history as the single most important engine development project, strategic market share gain and opportunity for diversification partnerships in Cummins history.
The Cummins B-series is a family of four- and six-cylinder inline engines known as the “one-liter per cylinder” in both the popular 3.9L four-cylinder and 5.9L six-cylinder engines. The B-series is widely used in many segments, including pick-up trucks, buses, military vehicles, marine and construction equipment resulting in millions of engine sales.
The first engine (a four-cylinder B) rolled off the line July 1, 1983 and the focus by Cummins was to manufacture a “bulletproof,” trouble-free diesel, especially with the vivid memories of the troubled “V” engine series in their recent history. The 3.9L engine began its MY in 1984 as an agricultural engine for use in Case equipment. The B series was actually a joint venture between Cummins and the (troubled at the time) Case that imitated a new company called Consolidated Diesel Corp (CDC).
The B series engine family was a huge departure from Cummins’ typical large diesel core competency – and a huge gamble that paid off, resulting in more than 20 percent of Cummins’ current total production. As a result, Cummins took a huge step toward liberating itself from total dependence on the heavy-duty engine market.
Initially, Cummins needed one or more high–volume customers in the intensely competitive automotive field to realize success or the losses would be of monster proportions. After nearly a four-year pitch to Chrysler, which at the time did not have a diesel pickup like Ford and GM, the deal was done and the 5.9 B engine would go into the 1989 Ram pickups.
Chrysler did not have the engineering staff available nor with diesel experience so the responsibility fell on Cummins with nearly 20,000 engines built in 1989. Cummins actually had to prototype the first 30 vehicles for Chrysler with a new subsidiary called Cummins On-Time Assemblies (COA). It marked the first time that a medium-duty diesel engine had been used in a light duty truck. This was the only diesel that had a GVW rating of 66K limit.
Everything that anyone will ever need to know about any Cummins diesel engine can be found using the CPL (Control Parts List) on the engine data plate. The CPL identifies the performance of that engine and related parts, including the rated power at rpm and fueling rate. For the 5.9L it can be found on or near the driver side of the timing cover; combined with the engine serial number you’ll have all you need to know for a full “birth certificate” with DNA information.
In doing the research for this article I was pointed toward a book “The Engine That Could” by Jeffrey Cruikshank and David Sicilia that outlines the 75 years of Cummins history. It is a great read and I would highly recommend it for anyone in the automotive engine industry. In this article we will focus on the six-cylinder 5.9L engine that most of you would be familiar with in the Dodge Ram pickup applications. Overly simplified, there are two engines: the original design (two valves per cylinder) and the ISB (Interact System B-Series) with 4 valves per cylinder.
The first cylinder block design for the 6BDT 5.9L (aka the Cummins “12 valve”) was the first member of the B series family to be used in a light-duty truck. The first series engine block, although developed in 1983, was used in the Dodge Ram beginning in 1989 through 1997 and-a-half.
- Figure 1 First design 6BT 5.9L “12 Valve” Cummins block.
- Figure 2 Second design ISB 5.9L “24 Valve” Cummins STORM block.
Much of the engine’s proliferation had to do with fuel injection pumps and not block casting. The difference between this engine and the second design are clear when you look at the blocks side-by-side (Figures 1 and 2, above). While there is a large amount of casting numbers for this block, for ID purposes they are basically meaningless: it is the visual ID that is important.
The second design block, the Straight Thread O-Ring Metric (or STORM), was used beginning in 1997.5 through 2002. This block was also used in 2003 and newer off-highway applications. In 2003 the common rail fuel system awas released which used a different block (not pictured) and continued into the introduction of the new 6.7L engine in 2007.
This is the ISB 24 valve engine block application and has numerous components bolting directly to the block for maintaining compactness as well as NVH. It produced up to 235 horsepower with the Bosch VP-44 fuel system and 325 horsepower with 610 ft. lbs. of torque with the common rail fuel system. Again, there are many casting numbers but visual ID is the manner in which you will determine what it is that you have. As before, those differences are clear when looking at Figures 1 and 2.
The first design crankshaft is forged steel with induction-hardened journals and eight flywheel bolts. The thrust flange is on the number 6 main journal. This crankshaft was used in the “12 valve” engine beginning in 1983 and was used from 1989 through 1997.5 and 1995.5-2002 in the Dodge Ram applications. The difference is obvious and apparent when looking at Figure 4.
- Figure 4 The upper most crankshaft is the first design used from 1983-1997.5 and from 1999.5-2002 for Dodge applications. The crank in the middle is the second design with the crankshaft position sensor trigger ring that was used from 1997.5-2002 for non-Dodge applications. The lower inlay shows the that the trigger ring is two pieces and can easily be replaced without crank removal.
The second-generation crankshaft is forged steel and induction hardened as well. It also has 8 flywheel bolts and includes two dowel pin holes for flywheel location. This crankshaft was used from 1997.5-1999.5 for Dodge and 1997.5 through 2002 for non-Dodge application. In Figure 4 you’ll notice the slightly different relief as well as other differences. This crankshaft uses a bolt-on crankshaft position trigger ring, which is manufactured in two pieces. It could actually be replaced in-chassis if it needed to be done that way.
The earliest connecting rod used in the 5.9L Cummins has a hole in the top of the tapered pin bore and a matching bushing for lubricating the bottom piston crown. This connecting rod wrist pin area design uses a tapered pin bore connecting rod. Cummins has since replaced the wrist pin bushing with one that no longer accommodates the lubricating hole so the first design becomes fully interchangeable with the second rod.
At the crankshaft end of the connecting rod the use of a common upper- and lower-half rod bearing is worth noting since the third design does not have this design. This is a forged steel connecting rod with a “tongue and groove” type parting line, used in 1985 and 1986, but never got to the Dodge Ram. See Figure 5 and Figure 6.
- Figure 5 The first and second connecting rod designs were identical except for oil hole in top as shown in inset. The third design rod has additional material in the forging at con rod bolt boss. All connecting rods use a tapered pin boss area.
- Figure 6 The first and second series rods have “tongue-groove” design rather than the “cracked” parting line of the third design. The third design rod also has mirrored machined bearing tangs and uses two different bearing halves between upper and lower (see inset).
The second design connecting rod is the same as the first except it has no oil hole in the top of the pin bore. It does have a different casting number, but as with most Cummins components it is not necessarily the identifier you would search for. It is the oil hole in the wrist pin bore that tells all. The non-drilled rod is the only one used in Dodge ISB applications (see Figure 5 and Figure 6).
The third connecting rod design is also forged steel but the parting line is a “cracked” design. This rod however does not use the same upper and lower rod bearing because the bearing locator tabs are on the same side of the rod since both the upper and lower halves are machined in a single operation. This rod also has additional material on the beam of the forging in the area for the rod bolt boss. This rod was used beginning in 2002.5.