Gordon Allen is something of an engineering adventurer. His various achievements over the years in the pursuit of engineering enjoyment and motor sport pleasure include designing and constructing a two-cylinder, twin-overhead camshaft racing motorcycle engine, constructing upon Mini gearboxes two four-cylinder, 1.5-litre alloy block engines fitted with adapted Jaguar twin-cam cylinder heads and placing one in each end of a racing Mini, making his own eight-port alloy cylinder head for a Mini complete with his own fuel-injection arrangement and now his latest trick is to adapt a Ford-BDA cylinder head to his own designed arid manufactured block and crankshaft assembly to create a 16-valve, five-bearing, dry-sumped, racing Mini engine. Several Allen BDA-engined Minis are racing successfully, including that of Peter Kitchen, in which Allen has an interest and which I was fortunate enough to try at Silverstone last year (but that’s another story).
However, constructing engines is really a hobby for Allen, who runs Allen Tool and Engineering Ltd., from Slough Trading Estate (Slough 23782). It is a hobby which led him by chance into the manufacture of crankshafts and his small engineering works is becoming widely known in competition circles for the quality of his nitrided steel crankshafts machined from solid billets. Many leading engine builders use his crankshafts in Formula Two, Three and Atlantic Ford BDA engines, but his manufacturing capabilities spread far beyond these modern racing realms into vintage and historic crankshaft manufacture. He can make any crankshaft so long as it is not too big for his machines and provided a drawing or preferably an actual example (even broken) of the crank required is available.
The beauty of Allen’s business to racing engine builders and vintage enthusiasts is that he is interested in small quantities and one-offs, in direct contrast to most businessmen who talk in thousands. Machining crankshafts from the solid is a long process, each machine has to be reset several times for different parts of the process and might just as well be set for an entirely different crankshaft as the same all the time. Allen likes the one-off work, finding it interesting and while he doesn’t want large quantities of particular types of crankshaft, obviously he requires a good throughput, preferably mixed. He feels that the mixed market is the one which needs Serving, for very few people have really concentrated on billet machining. As he says, there are plenty of firms with orthodox crankshaft production equipment who can produce cranks from forgings for Fords and one or two other popular cars in batches of 100 at very competitive prices – but they have to make more than 100 to pay for the forging dies. The man with a wornout or broken Maserati Type 60 or 61 Birdcage crank is hardly likely to wish to purchase 100-off just to obtain one—and Allen has been able to satisfy three Maserati customers with both Z and 2.8-litre four-cylinder cranks. Similarly he has produced a small batch of 4.1/2-litre Bentley cranks, a batch of pre-war Aston Martin 1500 c.c. cranks (he’s not sure for which model) and recently racing driver John Miles commissioned him to produce some pressure fed Austin 7 two-bearing cranks. Again, his type of service means that the Brian Harts of this world can commission him to make one-off experimental prototypes at no more cost than his “production” F2 cranks.
Short-stroke modern racing cranks are a piece of cake for Allen, but the 140 mm. stroke Bentley cranks proved a little tricky. If he were to do any more of these he would evolve a different technique, as well as estimate the cost correctly, because he lost money on all of them! As there are a lot of Bentleys around which at some stage might need his services he intends to look into the production of these massive crankshafts more closely.
Surprisingly, F2 BDA cranks are amongst the cheapest of Allen’s cranks, their small size allowing a retail price of roughly £160 plus VAT. A traditional type of 2-litre, four-cylinder crank with long stroke and much metal, like the Maseratis, would be £250 to £300. Obviously anything which is ultra-sophisticated with lots of cylinders is going to be pretty expensive, as must have been the 240Z Datsun crankhe made for Rob Grant, which I have heard praised many times. Costing is made even more difficult currently by the fluctuating cost of steel, indeed obtaining steel at all is a terrible problem at the moment. He is looking into the possibility of buying steel from Europe at roughly twice the price, but as he says, it’s available, and the most expensive thing which could happen to him is not to have any steel at all.
For a company the size of Allen’s the crankshaft business represents a fairly substantial turnover, built up over the last two or three years. He believes that there is considerably more potential ahead, for now that the word is spreading he is beginning to receive enquiries from abroad – even a phone call from California. Whilst he has been “playing with cranks”, as he puts it, his partner, Philip Allen (no relation) has continued with general sub-contract engineering to keep the wolves at bay, making things like valve bodies for BOC Welding torches.
All the crankshafts produced by Allen are machined from EN 40 B nitriding steel, a material which when heat-treated to the right condition gives a combination of good core strength and, when nitrided, a very high surface hardness. As has already been said, for the small quantities of each type produced forging cannot be entertained because of the die costs and experience has shown that crankshafts machined from the solid in the correct material are quite adequate for even the most arduous racing conditions. Allen believes that all Ferrari production and racing Cranks are produced in this fashion, so what is good enough for the Commendatore can’t be too bad. To avoid wastage, billets are purchased which correspond as closely as possible to the intended diameter and length of specifically ordered crankshafts. These fully heat-treated billets are then centred to suit the number of cylinders and the stroke, a precise operation done on a machine with accurate pitching equipment. The billet is then rough machined to remove the black scale left by the heat treatment and is transferred to a lathe on which the big end and main journals are roughed out, a fascinating operation in which the crank revolves eccentrically as the cutting tool gradually cuts its way through the deepest part of the circular billet until the journal takes a rough shape.
From this hard-worked lathe the billet is moved to a band saw on which the webs are shaped and the lump of steel begins to look more like a crankshaft. Another special cutting tool cuts down the web interiors to give clearance on either side of the journal before the journals are semi-finished to with in about in 1/8 of finished diameter. This is the end of the steel’s most punishing machining treatment, so at this stage the crankshaft is stress-relieved in a further heat treatment operation. Resultant scale is removed by sand-blasting to give the crankshaft that familiar dull grey look of steel in its natural condition. This stress relieving results in slight distortion, necessitating further light machining to restore the concentricity. Oil ways are drilled and tapped for plugging, tne big-end journals are finish ground on a special crankshaft grinding machine, the centres are removed from the two ends of the crank on a centre-lathe and the main bearing journals, sprocket and pulley nose diameters, flywheel seal diameter and oil-seal diameter are pre-ground on a conventional crankshaft grinder. Subsequently the crank is sent to Laystall’s for nitriding which takes about seven days because Allen specifies very deep nitriding of about 25 thou. radially. When returned to Slough the main journals and the various other diameters are finish ground to size, the big-ends are polished, the crank is cleaned, greased or dipped in a rust-preventative oil, wrapped, put in a box and this splendid piece of engineering is ready for fitting in an engine. Balancing is not carried out because usually the engine builder wants to balance all reciprocating components together, so he can take them to any commercial balancer. As it happens, these billet-machined cranks are somewhat better balanced inherently than forged cranks because they are machined all over.
Any crank, be it forged or cast iron, can be replaced by a machined crank. So long as the dimensions are correct it doesn’t matter how it is made. Indeed, to exemplify this, the original Maserati crankshaft drawings possessed by Allen proclaim the item to be nitrided steel, yet one of the originals delivered to him was cast iron, though machined all over. Iron cranks cannot be nitrided. They can be chill hardened, but never achieve the core strength of nitrided EN 40 B steel. However, iron remains a good crankshaft material up to a certain stress point. For instance the Ford twin-cam iron crank, light, like all these Ford iron units, is quite safe up to about 7,000 r.p.m. on an engine pushing out possibly 140 to 150 b.h.p. Nitrided steel is thus essential only for reliability with freakish revolutions and power outputs.
Forged steel cranks are more practical for large scale production (as on the scale of the original Cooper “S”) than machined billets because of speed and less metal wastage, but according to Allen neither method has any real final benefit over the other. Theoretically forging is reputed to be a little bit stronger in the same material because it is claimed that the grain flow goes round the profile of the component, while with a billet the grain runs down the crank and machining cuts right through it. In practice Allen doesn’t believe this theory to be of any relevance, simply because his billet cranks are subjected to extremely high loads without breaking. And after all, Ford forge their own BDA competition cranks, but do not incorporate forged big-end journals: they are left solid so that the stroke can be machined to choice. Keith Duckworth, on the other hand, is a purist, says Allen, and has Cosworth cranks forged as close to the finished size as possible, though sacrificing the ability to vary the stroke much.
Currently Allen is experimenting with new designs of the Mini-BDA five-bearing crank and the long-stroke three-bearing British Leyland-pattern cranks he makes for 1450 c.c. rallycross engines. He has experienced trouble with the taper flywheel mounting which appears to be something of a marginally safe arrangement with the torque these engines put out—over 100 lb. ft. in the case of the 1300 BDA Mini. On both cranks he is attempting to reduce the flywheel weight to the absolute minimum to reduce the flywheel effect on the end of the shaft. He is doing this by bolting on the starter ring with three sheet metal lugs, taking the flywheel down to the clutch lining overall diameter and thinning out the pressure plate. Some flywheel effect is of course necessary and this is achieved in the case of the BDA Mini crank by leaving circular flywheel blanks on the intermediate webs and in the case of the big British Leyland crank, by leaving much more metal than normal on the intermediate diagonal webs between 1 and 2 big-ends and 3 and 4 big-ends. The crank is thus left quite heavy, not for any strength reason, says Allen, but to give some kinetic energy spread down the crankshaft. “It seems logical that if you’re going to have a torsional vibration damper on the front of the crankshaft, this is in effect to take some of the load off, so if we spread it down the crank we may achieve a better result. We shouldn’t need a crankshaft damper either— we don’t use one on BDA cranks in any case. “A similar, but less pronounced flywheel effect problem has been encountered on short-stroke 1300 three-bearing engines, which he has hopefully overcome by “necking” the tailshafts on the cranks, reducing the overall diameter by 1/8 in. to 1.3/8 in., enabling the crank to wind up a little and give a little bit of a spring as a sort of torsion bar to take the bite out of the flywheel effect.
Allen took his first steps in engineering at Southall Tech shortly before the War. Several jobs, including one with the Glacier Metal Company, his first remote connection with the motor industry, saw him qualify as a toolmaker before the call of War dragged him off to the RAF. The intention was to make the young Allen into a pilot, which to some extent had been achieved, mainly on light training aircraft, when Whitehall saw that the end of hostilities was nigh and there was little use in spending taxpayers’ money on the likes of Allen if the lessons learned would never be needed. He was demobbed without flying operationally six months before VE Day and recommenced his engineering activities, this time in the film industry.
By this time he was very interested in competitive motorcycling, indulging in scrambles and trials with an AJS and a 250 c.c. Sunbeam. The Sunbeam was modified for grass-track racing at Brands Hatch in the days when the circuit went the wrong way and young John Surtees was helping his father Jack with his sidecar outfit. From grass-track racing trim the Sunbeam was converted for road racing, without notable successes and then in 1949 Allen turned his hand to engine building. This twin-cylinder air-cooled 250 c.c. unit with twin, geardriven overhead camshafts moving safely in ball races was made mainly out of simple magnesium castings, for which Allen had made his own patterns. The head and its finning was machined out of a solid block of magnesium. The engine went into a frame supplied by Bob Geeson, who had raced at Brooklands before the War and who was to ride the bike for Allen. He thinks Alan Dudley Ward and Geoff Monty made the special racing frame, very similar to a Norton and using Norton forks. Anyhow, the machine was entered in the 1949 Lightweight TT, but failed to compete because everything that could blow up, blew up in practice. Allen eventually lost interest in the project, but Geeson persevered, built further engines and raced them with reasonable success until about 1955.
Meanwhile Allen joined Joe Erlich on the old EMC motorcycle project, where there were a lot of managerial and directorship problems, which persuaded Allen to leave his eventual post as works manager to start his own business in 1953 or ’54. Competition motoring was forgotten whilst the business was cultivated, until eventually, as with so many other people, the advent of the Mini enticed him back. He bought his wife one of the newly-announced Minis in 1959 and when she decided not to learn to drive he found himself using it more than his Jaguar 3.4 (he always runs Jaguars—nowadays an XJ6 4.2) and fell in love with it. The inevitable happened, Alexander and Speedwell tuning equipment was added and the now 90 m.p.h. road car was persuaded into Brands sprints. Again the inevitable: more power was needed to be competitive so he cast around and found a Formula Junior BMC engine.
Fine, he had all the right parts, but of course the crankshaft didn’t have the right end on it to drive the Mini gearbox, and the cure for this marked the start of his crankshaft business. He grafted a tailshaft on to the nitrided Formula Junior shaft by using a copper-hydrogen brazing technique, which in the process annealed the shaft, run from then on in the soft state —and with 40 thou, undersize mains, necessary to correct distortion. Nevertheless it all worked and the result was a Mini engine with fantastic power for that era and certainly one of the first 1000 c.c. Minis around, for the Cooper had yet to be born. Later the FJ block was increased to 1150 c.c., but when a certain Rod Embley managed to beat him with a 1000 c.c. car Allen went back to the drawing board and developed his first pushrod Ford-engined Mini, utilising the Mini gearbox. limbley was persuaded to drive this 1500 c.c. car and had a very successful season, winning most of his races. But at the final race at Mallory Park a rod exploded through the side of the block and that was the end of that. Allen being Allen, something else had to be evolved in its place and this was when the twin Jaguar-engined car appeared in front of a startled Brands Batch public. Prior to this he had built the Mini-SCA engine – the s.o.h.c. Cosworth-Ford Formula Junior engine mated to a Mini box—for Janspeed, and later built a second example.
Patterns and castings were made and machining completed on a pair of aluminium cylinder blocks for the Jaguar engines, which were mounted on Mini gearboxes modified in much the same way as that for the Ford engine—in fact the front gearbox came off the Ford engine. It was Allen’s intention to fit a pair of Lotus-Ford twin cam heads straight on to the blocks, but at that time they were virtually unobtainable and the Jaguar alternative was formulated. The Jaguar cylinder pitch turned out to be the same as the Ford except for the wider pitch between the middle cylinders. His answer was simple enough: cut out combustion chambers four and five and close six up to three. Water flow was rectified by argon arcing an aluminium plate across the cut off. Great care had to be taken to keep the camshaft bearings in line, destined to carry pairs of cams made to FPF Coventry-Climax profile, the “in” engine at the time. For the first time he was forced to make crankshafts out of solid billets, the first of many.
The engines went into his existing Mini shell, both mounted in Mini front subframes on conventional Mini suspension, that at the rear made non-steering by locking the track rods. Gearbox linkages proved difficult, but clutch operation was achieved easily (but heavily) by fitting a bigger master cylinder and two slave cylinders. Each end had its own radiator. As for synchronisation, apart from setting throttles and carburetters identically, the only synchronisation was afforded by the action of the tyres on the road.
Amazingly the concoction worked very well on its few outings and in its best race, driven by Rod, achieved a second to Doc Merfield’s V8 Cortina. Indeed, it held the Brands Hatch three-litre lap record for a long time, mainly because few other cars ran in that class! Its two 1500 c.c. engines produced a total of 224 b.h.p., one with 107 b.h.p. and the other with 117 b.h.p., all at 6,000 r.p,m., the limit of the Jaguar valve springs. Handling was not one of the four-wheel-drive Jaguar-Mini’s strongest points, but its knell was tolled not by this, but by disapproving regulations which frowned on an engine mounted in the back seat under a lowered roof line. A similar experiment was subsequently carried out using a highly-tuned 1000 c.c. Cooper “S” engine in the front and a torquey 1300 c.c. unit in the rear in an attempt to cure understeer. Unfortunately such a layout led to a very high polar moment of inertia and the twin-Min would spin like a bolas when cornered too hard.
Illness kept Allen quiet for a while, the twin-Min was broken up and the Jaguar engines went to Janspeed and subsequently out of the country, where somebody must have encountered a dreadful spares problem. Allen had nothing more to do with racing until Dave Brodie, remembering his earlier engineering exploits, asked him to make a long-stroke crank for his original twin-cam “Run-Baby-Run” Escort. Allen’s fears that the crank would not stand up to the strain proved groundless: it ran on and on to win some sixty races for Brodie and resulted in Brodie’s engine builders, Race Engine Services, requesting Allen to make F2 and Atlantic cranks. Some early problems were encountered, largely because a sub-contracted crankshaft grinder spoilt the critical radii in the corners of the journals. Since then he has insisted on carrying out his own grinding, with successful results.
His reputation spread, demands came in for special stroke Mini cranks as well as Ford and the crankshaft business has continued to grow ever since. From this has grown the BDA-Mini business, largely because some friends of his persuaded him to resurrect his aluminium block. This has been strengthened a little but is fundamentally the same pattern as the original unit, though not normally 1500 c.c. He reveals, however, that he has just built a 1500 Mini-BDA unit for a customer, its 72.6 mm. stroke being as long as can be accommodated using a Ford-type crank in a Mini gearbox. It could be bored out from 81 mm. to 83.5 mm. to give nearly 1600 c.c., but as the 1500 unit on a moderate camshaft is giving 182 b.h.p. at 8,500 r.p.m. and 120 lb. ft. at 7,000 after detuning to keep the torque down, the poor Mini gearbox is likely to have sufficient problems on its hands. As is the driver, one would imagine…
Allan’s engines are perhaps the most revolutionary thing to happen to racing Minis since the introduction of the Cooper “S”, yet he professes not to take them seriously: “this is really fun”. To him its just another interesting engineering exercise, and -a hobby, for the engines are built in his spare time. He is always interested in other people’s adventurous projects too, like the three-wheeled sprint projectile beautifully engineered by a friend of his, which has a supercharged 1200 c.c. pushrod Ford engine running on nitro, an Allen crankshaft and drives through a special Borg-Warner torque converter. Recently he has made a special crankshaft for a driver who is mating a 1000 c.c. Imp engine to a Mini transmission to be mounted in a racing Mini, the type of project which is just up Allen’s street.
Gordon Allen seems quite unable to leave engineering alone for one moment. After working on crankshafts at his Slough factory all day, he spends his leisure hours in his comprehensively equipped workshop at his Gerrards Cross home, “just playing around”, as he puts it. But if his playing around results in things like his Mini-BDA engine, one tends to wonder what will come out of his workshop next.—C.R.
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