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The ‘X’ Factor-Origins of the XPAG

The ‘X’ Factor.
( Or even XPAG. )


In the UK there are many modern car owners who would be amazed to realise their all-aluminium alloy, vee-eight engine fitted to their Rover, dates back to the USA and was designed in the 1950’s. I refer to the General Motors Engine as fitted to the Buick Skylark, Special, Pontiac Tempest, and Oldsmobile F85 Cutlass. The rights to re-manufacture this family sedan engine by Rover dates back to 1965. It was seen later in the MGB GT V8. Similarly, there are lots of overseas owners of M.G’s who would be amazed to realise that engine’s they thought were exclusively an MG product, were in fact borrowed from a staid, mass produced Morris saloon car.


In 1935 the small M.G. factory in Abingdon in Berkshire, ( now Oxfordshire,) England, had a bit of a shock. Whilst the company had been doing well on the British racing circuits with their fast Little British Cars, production had become a rather ragged discipline. The company had been subjected to an internal re-organisation and had been ‘sold’ to the Nuffield Group. M.G. had been the personal property of William Morris, but his vast emporium had now got him into trouble with the UK income tax department, hence the new arrangements. This meant that now M.G. came under the management of the Nuffield Directors. The senior manager who was now in control of M.G. was one Leonard Lord who did not agree with ‘wasting time and money on racing cars’. Companies exist to make profits for their share holders, not to squander it on playing games, was the view of the new management.


Along with M.G. now having to drop many of their less profitable lines from the numerous models and variations they listed, was a decree that all M.G’s must now use in-house-corporate components. This resulted in the tiny ohc M.G. Midgets and various four and six cylinder specials stopping production. Kimber was not too worried as he had long sought to get M.G. upmarket with big, fast, well appointed saloon cars, and the results of this aim were the very elegant six cylinder SA and later the W.A. The VA with its four cylinder engine was a bit dumpy, but affordable. Under the skins of these cars were components straight from the Nuffield production lines of the Morris and Wolseley saloons. Morris were nearly always side-valve ( sv) driven, with Wolseley using overhead-valve ( ohv ) conversions of the same engines. The family of engines from the Morris Engine Branch were all inter-related. Many parts were common to them all, such as the tappet blocks with four cam followers in, two sets to a four cylinder, three to a six. Connecting rods, cam profiles, valves, guides, pistons, were all common. Even the stroke of many Nuffield/Morris engines dated back to that historical UK car, the Morris Bull Nose ‘Oxford’ and ‘ Cowley’ saloon, of 102mm. The basic engines in the SA and WA were straight from the Wolseley 18/80 range, and that for the VA was from the Wolseley 12/48. That of the Wolseley 12/48 refers to twelve horse power range, ( 12hp,) with 48 brake horse power. The 12hp refers to the road taxation group for the exchequer, not the actual engine power. Common ‘sizes’ in the 1930’s for UK cars were 7hp, 8hp, 10hp, 12hp, 14hp and 18hp, and road tax was charged based on this. ( The ‘hp’ tax was ancient, devised by the Royal Automobile Association, or RAC, early in the century when engines were feeble, and it used the bore but ignored the stroke. Hence the number of small-bore UK engines.)


Unusually for Morris, the equivalent to the Wolseley Twelve/48 also had an ohv engine. This Morris was called a 12/4, meaning 12hp four cylinder just to be awkward. Next down the range of the Nuffield line up was the Morris 10/4, a 10hp car with four cylinders. The Wolseley equivalent was the Twelve/40, 12hp with 40bhp. For the uninitiated, Wolseley were always the ‘better equipped’ version of the more mundane ‘cooking’ Morris. The Morris 10/4 was about to become part of the M.G. empire in a similar manner to that of the first M.G. I doubt if any Morris or Wolseley was ever exported to the USA, they were far too ‘English’. These two makes will not be familiar to Americans, but M.G. relied heavily on their components. Morris, Wolseley, M.G. and Riley made up the ‘Nuffield Group’. M.G. and Riley were two very small parts, Morris however was massive. Along with Austin they were then the two biggest UK car manufacturers.


Due to the decree of Leonard Lord banning small scale specialist component runs, M.G. were forced to use the running gear of the Morris 10/4 from 1935 in their new sports car. Brakes, steering, instruments, engine, gearbox, axles, etc, were all Morris 10/4 series 3 components. The engine was of a very long 102mm stroke dating back to Veteran Morris days with a 63.5mm bore with a cork clutch running in oil. Not a good recipe for a sports car engine. The five-port cylinder head was a casting adapted to what had originally been a side valve unit. The engine was slow to accelerate and had poor top end performance. It was never intended to be a sports car unit, and only fate had put it into the 1936 M.G. TA Midget. It was reliable enough, and a good saloon car engine for a workhorse, but too heavily built for a 1935 new M.G. model. Its ancestry dated back to 1923, and even further to the Hotchkiss-Morris engine of 1919.


Whilst M.G. were busy getting the TA into production, and pleased the engine was of 1292cc, bigger than the tiny ohc 847cc engines, Morris Engines were about to announce a better unit. The extra capacity made up for the poorer bhp per litre. Morris had for some time been looking at their engine range. It needed a full redesign. All of the range were developments of much older units, and it was time to invest in bettering them. The first group of cars to get an improved engine was the ten and twelve horse power range, ( 10hp, 12hp.) These were the most common size of car sold in the UK. Like any large company, no single person designed anything from scratch, that was far too expensive to put into production. Items had to be carried over as and when suitable. In the Morris Engines Design Office was a young man who had come from the Anzani Engine Factory, who built aircraft engines. He was obviously talented so was given the task of ‘improving’ the ‘M’ series of engines. This ‘M’ series was the MPJM in the Morris 10/4, the MPJW in the Wolseley 10/40 series 2, and the MPJG in the M.G. TA; in fact all the 10hp series. He was Claud Bailey, and his updated and improved engine was to be fitted into the then new chassis-less Morris Ten Series ‘M’ saloon, ( sedan.) ( Do not muddle up the chassis designation ‘M’ with the earlier engine series ‘M’.) The new engine was designated the Morris ‘X’ series of engines, and they were of 90mm stroke with a 63.5 mm bore. Note the bore, it meant the same pistons could be used again, and the machinery for boring the cylinders, as the TA engine. The ‘X’ series was not a new engine, but an improved one. It was of 1140cc with a modern dry clutch.


As the XPJM in the new Morris Ten series ‘M’, and the XPJW in the Wolseley 10/40 series 3 the engine took to the roads in 1938. By 1947 over 80,000 Morris Ten series ‘M’ had been produced, along with 12,000 Wolseley 10/40’s. During WW2 the engine was built and fitted to tens of thousands of utility units as petrol/electric sets, water pumps, etc for use by the armed forces. These can be identified by their prefix of XPJM/U. All these engines will also fit into the M.G. models that used the ‘X’ series. By 1939 the engine had been developed into a 12hp unit. It emerged with 1250cc with a 90mm stroke and a 66.5mm bore. This was a bored out 1140cc XPJM unit, but not quite. It had a stronger crankshaft, connecting rods, and pistons. The head had larger valves, and it was a real sweet running, easily revved unit. It went into the M.G. TB along with the improved Morris Series ‘M’ improved gearbox with remote control for the M.G. It was not used in a Morris 12hp model, as that range was dropped, the Series ‘M’ ten was very popular and selling well.


Claud Bailey had done a good job, his improved ‘X’ series of engines stopped being used by Morris and Wolseley in 1948. Morris went back to sv units, and many Wolseley’s got large ohc units. But M.G. continued using the engine and improving it until 1955, and one Wolseley used it until late 1956 as the XPAW. After WW2 in 1945 the XPAG 1250cc engine was put into the TC Midget, then in 1947 into the new Y and YT sports saloons. In 1949 it was seen in the new TD Midget, and by 1952 in the improved YB saloon. By 1953 it had been bored out to 1466cc in the TF Midget. In 1952 Wolseley had used the engine in their 4/44, ( four cylinder, 44bhp.) This car looks just like a taller version of the 1953 M.G. ‘ZA saloon, both are closely related. However the ‘Z’ saloons used an Austin engine, called the ‘B’ series.


As well as those ‘X’ series used in Morris and Wolseley cars, and all those utility engines, M.G. used quite a number. There were 379 in the TB; 10,000 in the TC; 28,643 in the TD; 1,022 in the TD Mk2; 6,200 in the TF; 6158 in the YA; 1301 in the YB, 877 in the YT; and 30,000 in the Wolseley 4/44. That in the 4/44 being a car not exported to the USA used the basic SC2 engine of the YB, ( SC meaning single carburettor.) That is a grand total of the engine’s production in the region of 182,600, not including those made as spares or for the war utility kits. The 1140cc engine can easily be bored out to 1250cc, but not 1466cc, that had required a re-core to move the cylinder centres.


Claud Bailey had lowered the reciprocating mass, improved the breathing, fitted larger valves with better porting, counter balanced everything, fitted full-flow oil filtration, shortened the stroke and designed in very modern cooling with water flow only through the head with the block using thermo-syphon. In the 1250cc he strengthened it all, and produced a real winner. There was a smaller version of 918cc that was used in the Wolseley Eight, 918cc being the older Morris 8hp engine standard size, but few were ever made. Claud went on to join the design team of another very famous ‘X’ series of engines in the late 1940’s when he moved to Jaguar. That was the Jaguar six cylinder, twin ohc ‘XK’ series used in the ‘E’ types and sports saloons.


Neil Cairns.