The 6.354 Story: The Making Of A Legend

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Posted on 2 December 2015

The 6.354 Story: The Making Of A Legend

If the P6 was the diesel engine that gained the early reputation for Perkins. The 6.354 restored the Company’s image following the R6 saga and provided the foundation for worldwide growth through the 60s and 70s.

The problems with the R6 had left Perkins without an engine for medium trucks that anybody wanted to buy, at least in Britain and the USA. During discussions with Ford in Detroit in 1957, Gordon Dawson, the then Director of Engineering, tried to sell the idea of the revised R6 for a new truck scheduled for production in 1960. Ford turned this down as insufficiently powerful, so Dawson offered the idea of a 120 BHP unit of a new compact design.

This was accepted with reservations. The design of the engine continued back in Peterborough with considerable urgency, based on a new concept where the auxiliary drive was taken from a small jackshaft driven at engine speed from the timing gears. This allowed the use of the new DPA fuel pump, mounted vertically and driven through a wormwheel and pinion, with the lubricating oil pump driven coaxially by a quill shaft below the wormwheel. The extension of the jackshaft then allowed auxiliaries such as compressors, vacuum pumps or hydraulic pumps to be driven at engine speed, mounted off the cylinder block and driven through a simple flexible coupling.

By using a low-positioned camshaft with long pushrods the timing case was kept small and allowed the water pump to be mounted above it, reducing the engine overall length, an important factor for trucks with engine compartments designed for V8 gasoline engines. Further reductions in the cylinder block length were made by paring water spaces between the cylinders to a minimum, and by using a bore dimension of just under 4 inches, coupled to the P6 stroke dimension of 5 inches. Thus an engine with a swept volume of 354 cubic inches (5.8 litres) was born, with an initial rating of 112 BHP at 2800 RPM.

Another significant change from the previous 6 cylinder engines was the introduction of direct fuel injection, using a toroidal chamber in the piston crown rather than the Aeroflow chamber in the cylinder head. This resulted in more power from the same swept volume while improving fuel economy. With accurately cast inlet ports in the head and the new CAV pump and injectors, new standards of smoke emissions were also achieved.
Development of the engine proceeded fast though not without problems. These included the wormwheel drive, cylinder head gasket, high oil consumption and crankshaft breakage. Production started in 1960 and, in 1962, over 24,000 engines were produced from a purpose-built facility at Eastfield where block, head, crankshaft and connecting rods were machined.

The engine was a hit for most applications resulting in versions to power trucks, tractors, industrial and marine equipment. The rating for vehicles was soon increased to 120 BHP at 2800 RPM, whilst turbocharged versions (designated T6.354) were developed quickly for MF tractors, marine and industrial applications.

The marine market proved especially attractive, with inclined versions of the engine being produced to fit below cockpits. Ratings of 150 BHP for general use were available, with much more for offshore powerboat racing where Perkins established an enviable position in the late 1960s.

During this period, many changes were made to the engine to improve its durability, including revisions to the cylinder head gasket, valve train and piston assembly. Further changes, which included modifications to the cooling system, signalled the ‘dot’ series of engines. Changes of bore size were also introduced to meet MF requirements for engine power matched to the machine or tractor. Thus there were successive introductions to suit various market needs:

  • 6.3541
  • 6.3542
  • 6.372
  • 6.3721
  • 6.306
  • T6.3543

Air-to-air charge cooling for the vehicle engine was claimed as another first on this size of diesel. For Mexico, where altitude caused considerable power loss and excessive exhaust smoke, a turbo-compensated version (C6.3542) was developed with considerable success.

One disappointment was the inability of Perkins to gain a lasting foothold in the American truck market. Although there was a reasonable level of penetration into some ‘pick-up and delivery’ sectors, there were service problems with the engines, some stemming from a lack of understanding of the actual market needs and driver habits. Sales stagnated and never reached the high expectations of Perkins in the early ’60s.

In the late 1970s, a major redesign of the cylinder block and head, plus changes to other components, resulted in the introduction of the 6.3544 and T6.3544 which eventually replaced all other versions. The changes included machined inlet ports and the elimination of the tappet side cover plates, bringing the appearance of the engine more in line with the 4.236 family. Rating rationalisation was also introduced as the increasingly stringent smoke requirements were addressed.

Production of the 6.354 was not restricted to Peterborough. As licence agreements were signed around the world during the 60s and 70s, production of the engine began in Mexico, Argentina, Turkey, Peru, South Africa, Brazil and the USA. The 6.354 became an engine locally available to customers across the world, using some parts supplied as kits from Peterborough. The level of ‘nationalisation’ varied, but gave an advantage to Peterborough where buying back components from overseas plants eased the supply position at times of high demand or industrial dispute.

New engine applications were appearing all the time, including special versions for Alvis military vehicles: the easy adaptation of the engine design and the ready availability of many conversion parts made the 6.3544 family the product of choice for customers both large and small.

The production of the engine in its various configurations in Peterborough alone rose to over 50,000 per year in 1969 and remained at levels around 40,000 per year from 1965 through to 1980. Volumes produced under licence around the world are not easy to separate out, but probably added around 20,000 units each year.

By the mid 1980s, the 6.354 was overtaken by the new 1000 Series. This was designed around the same basic 1 litre/cylinder but with radical changes to achieve tighter emissions standards and meet demand for metrication and the needs of a more sophisticated market. A number of base engine components were however carried over from the 6.354, proving that when something is right there is no sense in change for the sake of change.

As the new engine gained acceptance, and legislation tightened its grip, the 6.3544 volumes diminished. In 1996 the last engine came off the assembly track. A total of 1,018,307 engines were produced in Peterborough, plus significant volumes around the world. Many of these are still in use, proving the ability of this multi-purpose engine to give reliable, economical service wherever power is needed. There are not many engines that can claim a production life in excess of 36 years, although the Perkins P3 can now claim over 50. But that’s yet another story…