THE 4.236 ENGINE: UNSUNG WORKHORSE.

Perkins had relied on the P4 engine during the years after the war as the power unit for many applications from passenger cars to industrial equipment. By the end of the 1950s the engine was becoming outdated, with the indirect ‘Aeroflow’ combustion system becoming uncompetitive with new generations of engines from other manufacturers. In the late 1950s a decision was made to produce a four-cylinder version of the 6.354, applying the engine ‘family’ concept to the successors to the original ‘P’ series.

Consideration had to be given to every market sector. The business was moving rapidly from diesel conversions to original equipment fitment, with customers expecting a more modern sophisticated product with greater power, economy and compactness, plus ‘tailoring’ to suit their particular needs.

Design deliberations resulted in a decision to make two variants of the engine, aimed at the tractor and vehicle markets respectively. Use of either variant as appropriate to suit the more varied requirements of the industrial sectors would enhance the Perkins reputation for flexibility of application.

The tractor version was basically tailored to the needs of the parent company Massey Ferguson, having a cylinder block with cast-in adaptor for the transmission housing and starter motor position plus a heavier front end to suit the frameless tractor chassis. To combat vibration problems associated with a large capacity four-cylinder engine rigidly mounted into such a chassis, the engine incorporated a Lanchester balancer in the sump. Driven at twice engine speed and featuring twin counter-rotating weights, this unit balanced out most of the second order imbalance inherent in a four-cylinder in-line engine. The engine was closed with a massive cast iron sump, which also formed part of the tractor backbone.

The ‘vehicle’ cylinder block was of lighter construction with machined pads to accept the flexible front mounts common to vehicle installations, plus a rear face able to accept a variety of flywheel housings and adaptors, with alternative starter motor positions. The rest of the engine components were common wherever possible, although one exception was the crankshaft, where the separately balanced tractor engine could take a simple non-counterweighted version, whereas the vehicle crankshaft had integral counter-weights providing better balance at higher speeds. Many other parts were also shared with the 6.354, although the family concept did not extend to the fuel pump drive arrangement where the 4.236 had a conventional timing gear train with the fuel pump flange-mounted to the timing case.

The cylinder head took the 6.354 concept a stage further by incorporating machined inlet ports: this removed some of the inconsistency in air flow dynamics caused by variations in port casting. (This was one of the first benefits of basic research work on airflow being undertaken at Queen Street).

Development of the engine progressed through the early 1960s. As the design was finalised, a major factory extension was planned and executed, so that what became known as Factory Two took shape to the south of the existing Eastfield facilities. Prototype engines were exhaustively tested at Queen Street and in the field.

A late change to the right hand side of the cylinder block casting was made to improve block strength and ease some machining processes. This created individual push rod and tappet tunnels, and the now familiar block appearance, replacing a machined pad and cover plate.

In 1964 the new factory was formally opened and volume production started, reaching 2,553 engines for that year and increasing rapidly to over 60,000 engines by 1969.

Little has been said so far of ratings. The original target was for 80 BHP at 2800 RPM for the vehicle version and 65 BHP at 2200 RPM for the tractor version.

This was just a start however. Many variants of the basic engine were to follow, as the engine became the workhorse for many customers. MF demands included the need to tailor the engine capacity to the power output and stop the end-customer from up-fuelling the engine and overstressing the tractor. Thus the original swept volume of 236 cubic inches was soon followed by the 4.248 (3.975 inch bore in place of 3.875 inches) and the 4.212 (4.5 inch stroke in place of 5 inches). There was even a 4.204 with 3.6 inch bore to replace the elderly 4.203 but this never reached production. Turbocharged versions were developed and a gasoline derivative was designed for use in American-market lawn tractors and forklift trucks.

As a result of an agreement with Togyo Kogyo in Japan, short stroke, indirect injection versions of both the 4.236 and 6.354 engines were developed, the 4.224 and 6.335 respectively, these being exclusively for trucks in the Far East.

Further demands for tailored versions resulted in the creation of a heavy duty industrial with cast iron timing case and twin power-take-off positions. A plethora of new components, especially sumps, manifolds and rear end housings were designed to allow fitment into an ever-increasing and bewildering variety of machines.

As more licensee agreements were signed around the world, the 4.236 family of engines became the preferred product. New plants in Mexico, Peru, Turkey, Brazil, Yugoslavia, Japan, Poland and Korea all took this engine as their basic product, often to support local MF tractor production. Initially most components were supplied out of Peterborough as CKD (completely knocked down) kits. The capacity of Factory Two increased to support local production, which topped 95,000 engines in 1976, plus many thousands of kits for overseas. As components were approved locally for the overseas plants so the demands on Factory 2 eased, while the ability to ‘buy back’ components from the new plants increased the global flexibility to meet fluctuations in demand. An important factor in this achievement was the stringent design change control exerted to ensure a standardised product, without local variations, so that parts would fit wherever produced. Approval of local parts was also closely controlled.

As with the 6.354, there were numerous upgrades and product improvements over the years. However by the 1980s legislative requirements and competitive pressure demanded more radical change. The changeover to the 1000 series family was simultaneous for the 4.236 and 6.3544, although volumes remained high on the 4.236 family for longer. The last 4.236 to be built in Eastfield came off the assembly track in 2000, by which time a total of 2,190,838 engines (including all variants) had been assembled in Peterborough alone. This represents the highest production volume of any Perkins product, and probably doubles if all overseas-built units are taken into account!

The 4.236 family was the backbone of Eastfield production for nearly 30 years, powering more Massey Ferguson products than any other engine type, to say nothing of the huge number of applications for other major manufacturers and for small specialist concerns. The engine assisted the modernisation of farming methods in virtually every country in the world, as well as bringing mechanisation and improved efficiency to every corner. Yet this engine does not have a ‘name’ in the field that everybody automatically remembers! It really is the unsung hero, the ubiquitous workhorse that just keeps on running and running.

David Boulton August 2002.

The 'tractor' block version The 'vehicle' block version

The 'toroidal bowl' direct injection combustion system of the 4.236