Two Jaguar X120 engined “Specials,” Oscar Moore’s HWM-Jaguar and EP Scragg’s Alta Jaguar.
One of the more interesting and potent “specials” to appear in this year’s sports-car and club races has been Oscar Moore’s HWM-Jaguar. Its successes are rather too numerous to detail, but it will be recalled that at the last BARC Members’ Meeting at Goodwood, Moore won a scratch race at 74.61 mph, and was later placed third in a handicap, in which he established fastest lap of the day, at 79.85 mph. This puts him in the lead, one point ahead of FC Davis and the Cooper-MG, in The Motor Sport Brooklands Memorial Trophy Contest, the final round of which will be contested at Goodwood on July 26th.
At the Bugatti OC Silverstone Meeting on June 14th, the HWM-Jaguar, just returned from running at Dundrod, tied for second fastest time in the one-lap sprints and then, coolly won not only the unlimited sports-car race in which it was driven by Oscar’s son Terence, but the event for Formule Libre racing cars, setting up a new lap record for the “short” Club circuit of 74.62 mph.
Oscar Moore, whom we first met during the war when we were enquiring into the performance of the fwd Cord car, was interviewed about his HWM-Jaguar during the latter meeting—a most appropriate occasion !
The chassis and body are, of course, those of his 1950 HWM, one of the three team HWMs of that year. Into this compact chassis Mr Moore contrived to install an XK120 Jaguar engine, but an XK120 with a difference. Not only has this engine a special cylinder head, the high-lift camshafts and other mods associated with getting maximum power from one of these engines, but in its present guise it has been enlarged from 3,442 cc to 3,814 cc. This was achieved by boring out the cylinders, and linering them to a bore of 87 mm, an increase of no less than 4 mm. It was a daring expedient and so far, apart from the liners expressing a desire to shift, has paid obvious dividends.
The induction system is virtually standard and carries two 23/16-in SU carburetters, although 2-in carburetters would he nearer the ideal. The HWM radiator was modified to suit the bigger engine and is slightly pressurised. To the Jaguar engine is mated the original clutchless Armstrong-Siddeley pre-selector gearbox, altered somewhat internally because the HWM ratios were closer than required with the 3.8-litre Jaguar engine. The HWM rear end has been rebuilt with stronger Hardy-Spicer drive shafts and hubs and now incorporates a Jaguar final drive and differential unit, which provides Oscar Moore with a choice of axle-ratios, 3.27, 3.64 and 3.9 to 1. On the occasion of our interview he was using a 3.6 ratio in conjunction with 6.00-16 back tyres (5.25-16 on the front wheels) but confessed that his 3.9 to 1 axle is better suited to the Silverstone Club circuit. The gearbox ratios are 3.0, 1.81 and 1.37 to 1. The large HWM fuel tank was removed from the rather stub tail of the car and by using a 17-gallon tank the spare wheel can be accommodated horizontally ahead of it, to satisfy the hawk-eyed scrutineers who descend on competing cars at sports-car meetings. For illumination, however, Oscar relies on two tiny side-lamps mounted on the front-wings stay, as our photograph discloses: The engine exhausts into two business-like silencers-cum pipes terminating ahead of the back wheel on the near side.
Installing the Jaguar engine meant that much weight was imposed on the HWM independent front suspension but this has stood up satisfactorily, aided by a stronger Woodhead leaf spring. The HWM-Jaguar weighs. 171 cwt with oil and water but sans fuel. Distribution is about 50/50 between front and back wheels.
The engine is run on 80-octane fuel and Castrol “R” oil, and Lodge 47-plugs-and a Lucas magneto are used. It is reluctant to exceed 5,000 rprn, which Oscar Moore observes as his limit on the indirect ratios. He has had no time to convert it for methanol fuel but has interesting development plans in mind, such as the use of a Type-C cylinder head, camshafts of mere “racing” contour and a reduction in compression-ratio from the-present high figure of 9.37 to 1.
In its existing tune, however, the HWM-Jaguar has shown itself to be very worth while and Oscar Moore has every reason to be proud of his car. We have not had an opportunity of driving either this car or EP Scragg’s Alta-Jaguar (which retains a standard-size XK120 engine and, we imagine, is about 1 cwt heavier than Moore’s) but it is obvious that they must be as exciting on the road as they are round the circuits.
I first saw EP Scragg’s Alta-Jaguar last winter, when I visited HW Motors to have a sealed-lips look at the chassis of the 1952 HWM. For the Alta chassis into which the XK120 engine was being installed is none other than that of George Abecassis’ GP car.
Scragg, who, like the famous Basil Davenport, is a native of Macclesfield, had the misfortune, in May last year, to suffer a road accident with his XK120 Jaguar, which was in pretty potent tune, as ascents of Prescott in 51.1 sec, and Shelsley Walsh in 44.1 sec, testify. No Jaguar has yet improved on these times, incidentally.
Such an engine seemed too good to waste, so Scragg hit upon the happy idea of asking HW Motors to install it in the ex-Abecassis Alta, this being deemed to have a more suitable transmission and to be better suited to the power output and torque of the Jaguar engine than an HWM chassis which was also available.
Accordingly, the chassis was rebuilt, the wheelbase being shortened to 7 ft 10 in, and fully modified to the latest Formula II trim by Alta themselves. The new rear-axle, designed to withstand 300 bhp and incorporating a ZF differential, was installed, and the Alta steering changed for the latest HWM rack-and-pinion layout. The engine, obviously very potent, was prepared by Hugh Howorth, whose own XK120 proved during last season to be about the fastest in England. Pistons giving an 8.0 to 1 compression-ratio, modified and polished internals and high-lift camshafts produce the power and to cope with it a heavy-duty clutch and lightened flywheel are used. The ratio of the back-axle is 3.89 to 1 which gives a second gear of 7.67 to 1and a third gear of 5.28 to 1. In conjunction with 6.50-16 rear tyres (those on the front wheels are 6.00-16) this represents maxima of 70 and 100 mph, respectively, at a little above 6,000 rpm, with a maximum in top gear in the region of 140 mph. It is thought that such gear ratios will prove well suited to all-round competition work, being admirable for hill-climbs and about what is wanted for our short racing circuits.
The Alta chassis provides all-round independent suspension and Scragg enjoys a very smooth ride, while the steering is very accurate, pointing to correct weight distribution, always rather a gamble when constructing a hybrid of this kind. The brakes the owner dismisses briefly as “just wonderful.”
The body was built by the Leaeroft Eng Co of Egham, who also make the HWM bodies for John Heath. It is a comfortable two-seater with an admirable hood, spare wheel within the tail, and quickly detachable windscreen replaced by aero Screens. The finish would put many production sports-cars to shame.
At first the engine lost power badly at high rpm, but this was rectified and the Alta-Jaguar formula is now beginning to pay dividends in competition. For instance, at the May BARC Goodwood Members’ meeting Scragg finished third in a scratch race to Oscar Moore’s “outsize” HWM-Jaguar and an XK 120, making fastest race-lap at 76.32 mph. At the Maidstone and Mid-Kent MC Silverstone Meeting the car won a scratch race at 61.24 mph over the “long” 1952 Club circuit.
Scragg feels that he was wise to choose the Alta chassis, which has proved very reliable, and he hopes eventually to obtain approximately 200 bhp from the Jaguar engine, when his Alta-Jaguar will be even more worth watching than it is at present..—WB.