The 500 Series diesel cost Leyland a packet – and not just in development costs.
Mike Humble tells the story of this ‘interesting’ engine
Fixed head asset
CONTRARY to modern day belief, Leyland Truck and Bus was once a formidable force on a truly global scale with British trucks and buses operating in all four corners of the world. At the helm was Donald Stokes, a man reputed as being a true statesman, gentleman and entrepreneur whose father was the General Manager of Plymouth Corporation Transport, buses and engines were in his blood.
Today, we think of Leyland or British Leyland as a joke with misty eyed fondness, but before the formation of BLMC this Lancastrian based empire ruled the roads both here and overseas with an enviable reputation for engineering excellence and reliability. As the ’60s progressed a dark cloud was on the horizon, at that time it was no bigger than a child’s soapy bubble, but foreign competition was building momentum and it was eventually to shatter the British Automotive companies – motor bikes included.
Leyland Motors as it was then known, was a shrewd operator and almost immediately after the formation of BL set upon making a range of diesel engines that were modern, powerful and efficient. At this time,Leyland’s biggest truck engine was the 11.6-litre `680` unit which could develop 220bhp but not without issues of failing cylinder head gaskets. Leyland advertised a position of engineering director with a brief to design and develop a new range of engines to meet and beat the competition.
The vacant post was filled by Dr Albert Fogg, an engineer formerly with MIRA. Dr Fogg was well versed in engine design but his train of thought was very much outside the box, so rather than work on a way of improving tolerances and existing designs (gaskets aside the 680 was a respected engine) Fogg set upon isolating the problem by eliminating the head gasket altogether. With his team of engineers, Fogg developed a high speed diesel engine that broke the mould in design terms.
A prototype engine of 700 cubic inches (12-litre) with a fixed head including an over head camshaft, cross flow manifolding and turbo started to be tested. With the engine having no separate cylinder head, maximum cooling to the piston crowns and combustion area was allowed. The engine was very slim compared to the Gardner and Leyland 680 units owing to the cylinder block not having to accommodate a camshaft, tappets or pushrods.
Because of this revolutionary design having far less moving parts, the engine operated at higher speeds, some 500 rpm more than the normal. Super slim fuel injectors developed by Ambac especially for Leyland offered a more controlled and higher pressure fuel rate into the cylinders. Light pressure turbocharging gave a useful amount of low down torque theoretically enabling good fuel economy and the small number of prototype engines were proving to be quite promising. A fly in the ointment came in the form of Leyland marketing men wishing to have an engine gearbox combination that weighed less than 1000kg.
This critical and fatal change of mindset caused massive upheaval in the design dept as the marketing men ordered the engine boffins to scale down the size of the engine and have running prototypes running as soon as possible. The fixed head power unit quickly became scaled down from 700 to 500 cubic inches and the National bus was to be the first recipient of this engine. Fogg, upset with the constant changes, quit his post and left British Leyland, leaving the design team leaderless, soldiering on with an unproven design that was prove a disaster.
The 500-series was hastily developed and put into service with the design team pleas with management begging for further proving falling on deaf ears. Senior BL management seemed to quite happy with making the customers do the development work for them, a trend that continued throughout most of the ’70s. Offering power from 200 to 260bhp, the 500 certainly offered superb performance, especially at the higher power ratings. The distinctive whining clattering sound played a different tune from the growling 680 or AEC 760 engines.
A brave face was put on by the service staff as the engine quickly became reknown for being troublesome and expensive to repair. The idea of having a fixed cylinder head was a brave one, but procedures such as getting to the valves for example required specialist tools and the separation of the cylinder block. The National bus which also received this problematic engine fared slightly better with lower rated engines.
NBC (National Bus Company) fleet engineers hated them and yearned for the service and forget nature of engines like the Gardner 6LX. Some municipal bus companies tried the National with firms from Cardiff, Nottingham, Northampton and Plymouth getting pretty good service from the 500. Experience proved that fleets with high standards in the workshops got the best experience from the 500. After worrying levels of warranty claims, Leyland set up an internal squad to get to the root cause of why the 500 was such a disaster. Quality control proved to be shocking with stories of gaps up to 9 thousandths of an inch in the engine block join would cause monumental oil leaks and blow holes in the castings contributing to many water leaks.
Manufacturing tolerances were in fact tightened up as time progressed, but the main reason for the failure of the 500 series boiled down to poor development and in some cases, sub standard parts. Confidence both in house and with customers waned as the problems of BL continued to pull the entire group ever downwards.
They were well known for being smoky, partly due to badly calibrated fuel pumps and in part thanks to the turbocharger being slow to boost. Overfueling was a common headache and for many years a 500 piston with a melted crown adorned my mantle piece. Such a shame, for this engine truly was a wonderful piece of design and technology, but as was the case with so many other BL ideas, badly managed, badly developed and simply left to soldier on. Bus companies who had suffered with the 500 quite often repowered the vehicles with other engines and Leyland towards the late ’70s seemed to admit defeat by offering a de-rated engine with 170bhp laughingly called the long life unit.
UK hauliers fed up with Leyland, bought into other marques offering Cummins or Rolls Royce engines while up in Scotland, the SBG (Scottish Bus Group) refused to buy any further Nationals. When the National series 2 was introduced in 1979, Leyland showed another sign of no confidence by offering a Gardner 6LXB engine and the Trojan 680 was developed into the L11 & TL11, the 500 died a quiet death. Customer loyalty was damaged beyond repair thanks to the 500 unit.
Around the time of the cancellation of the 500 series engine, some senior managers and engineering staff were taking stock of the turbulent situation in a meeting at Leyland’s HQ Lancaster House. Questions were raised about how and why this engine was designed in the first place and general comments about the long departed Mr Fogg discussed. One technical manager mentioned about the fixed head idea being used on a Bentley car many years prior, a colleague then barked, ‘…and aye, it never bloody worked for Bentley either’.
So was this design a total failure? Well on a personal level, the engine was certainly a feat of amazing design for the time, designed in a period where Leyand were a supreme force on a global scale. In terms of the National bus, the high tech factory and running gear saw many rival engineers visit the Workington bus plant and Leyand’s engine plant.
From a customer point of view, this marked a very important era whereby operators and owners felt that Leyland were forcing this untried and unproven technology upon them without consultation. Too many internal forces were pulling the company apart and where time should have spent on courting the customer and developing a product which worked, British Leyland lost their way, struggling in a world bogged down with debt and industrial strife. Managers and directors became fire fighters instead of industrial figureheads and as the quality of the product sank ever further, that small dark cloud I mentioned earlier became a storm as European competition set up stall and exploited the weaknesses of BL.
The Leyland 500 series could give decent results, but it was a poor solution to a problem that could have been, and in fact was, easily cured. It never really became a good engine, the standards of reliability was truly awful and it was only reknown for its spirited performance and clouds of black smoke.
Almost a decade ticked by with an engine that not even Leyland had any real confidence with. The reputation with the National for example, caused a flurry of activity with disheartened fleet engineers throwing away the 500 and replacing with either DAF, Volvo or Gardner engines. Oddly enough, operators such as Chase Bus in Staffordshire found the 500 to give excellent service, but as mentioned before, operators with exacting levels of quality often gained the best results.
Leyland designed and produced in line six cylinder high speed turbo diesel. Built at the Leyland Spurrier plant Lancs.
8.2-litre (500 cui)
170-260bhp in horizontal or vertical format
Overhead camshaft with bucket & shim tappets with constanst mesh timing gears & C.A.V/Ambac fueling system
Crossflow combustion with Holset light pressure turbocharger
Cylinder head casting integral with cylinder block and seperate block/crankcasing
Compressor and fuel pump drive take from the nodal point of the camshaft
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