Tuning topics: the cross-country sprinter—a 1.4-litre Cooper S

Since 1963 a young man from Shakespeare’s west country region has nearly exclusively devoted his talents to Mini derivatives and how the best can be wrung from the ubiquitous box in British club rallies. During the last two years his efforts have become so successful that 26-year-old Will Sparrow has become the only Mini-Cooper S driver to consistently beat the Ford Escort RS and TC models that have now established such a competitive edge in home events. In 1970 he became RAC Rally Champion, among other titles, whilst at the time of writing he had scored four outright wins in 1971 to lead the Motoring News/Castrol series by 9 points.

We have been fortunate enough to not only briefly try the 1,340-c.c. Clubman S-type which scored those victories, but also allowed to take away the 1,390-c.c. Mk. 2 Cooper S that Sparrow and his wife use for normal road transport. The latter car basically consists of the enlarged engine which, complete with a fresh camshaft and exhaust manifold, Sparrow is planning to market through his business as a routine item at £100.

To find out if the 120 thou. overbore that gives this extra 115 c.c. is a practical idea we were entrusted with the beautifully turned out red Mini-Cooper S for the best part of a week. Customers who present themselves at Sparrow’s small but neat garage will find that the work on an existing S-type engine (the normal Austin/Morris 1275 can be used, but there is a greater risk of porous bores) consists of Hepolite big bore pistons, BL Special Tuning 731 camshaft and long centre branch exhaust manifold, the latter item connected up to a standard exhaust system restored to the less restrictive earlier S-type specification. The larger Hepolite pistons are as manufactured for a normal production Triumph, having the advantage of lowering compression ratio to 9 to 1 so that four star fuel can be used regularly and the engine actually stops when the key is turned; usually the biggest of the S engines is prone to running-on after a hard thrashing.

To ensure that the new engine performs reliably a copper asbestos head gasket, now sold only as a competition item from BL, and new crankshaft bearings are included, as is the labour involved in stripping down and reassembling the most powerful of the A-series units. Hydrolastic suspension was fitted, mainly because this car was built up from a basic shell and fitted with whatever parts Sparrow could lay hands on at least expense. However, he obviously has the best contacts for the Mini’s ride was very well controlled as if competition displacers had found their way in along with Aeon bump stops at the rear. Wide rim alloy wheels manufactured by the Mill Accessory Group (which appropriately abbreviates to MAG) carried broad 165 section Goodyear Grand Prix radial tyres for our test, nestling under neat Cosmic alloy arches which carry the standard chrome trim. Thus the effect is as if the Mini had been designed for such generous tyre and rubberwear, so unobtrusively do these spats blend into the standard bodywork. As a matter of interest the car can be lifted by the spats, should you visit a ditch.

Looking round the car before the test, it almost seemed a shame to drive it away for the paintwork gleamed and the whole machine conveyed the air of being brand new. In fact the mechanical parts had covered many miles on various other Minis, some in competition. For example the front and rear subframes had already worked hard for 30,000 miles, yet the diminutive S also felt as though it had just emerged from the showroom when we set off for London.

Apart from a brief but exhilarating whirl in the rallying Clubman, it had been some time since this tester had driven a Mini at all. The result was that he gradually remembered all the old strong points and snags that any Mini-owner knows so well.

In production form the S-type was popularly reckoned to be the fastest way of getting around this crowded island, so long as the driver could stand the vigorous engine and transmission noises and the lumpy standard seating. Sparrow’s converted car obviously has its roots in the characteristics which made the S so popular that it became a lot more than just a “homologation special”, though the strong points of the 1275 S are even more strongly emphasised in this large-bore car. Outstanding road performance is provided because the increase in bore has allowed the engine to develop real power lower down the range, thus one finds that third gear is just the job for roundabouts and overtaking, whilst the modest exterior dimensions and terrific roadholding make both frustrating town and main road travel a joy.

In fact people who did buy a Cooper S (it’s now been axed of course, and enthusiasts are fobbed off with the far more docile 1275 GT) did so because they wanted to have some cheap fun, or because they were seriously interested in competition. The idea of Sparrow’s conversion is to boost the already strong points of the S, and thus one finds that the engine responds best to gear-changes well before the maximum r.p.m. allowed by the valve springs, whilst the wider wheels and tyres, together with the roll-free suspension, provide enough roadholding and handling to keep even the most youthful enthusiast on his side of the road!

Somehow I cannot imagine a Cooper S with the standard “tiller” that is fitted to the 850s as a steering device, and Sparrow’s car was no exception, the compact leather-rimmed wheel controlling a machine that has the reactions of a supercharged Go Kart. Obviously there is plenty of “straight-on” understeer pull when powering into a corner, but the wider wheels and tyres hitched to this bigger engine enable the car to be cornered in the same tail-out manner adopted by Sparrow in the rally car, and so beloved by the hotter Ford Motor Co. products. Really exuberant driving, especially with this 1.4-litre conversion, is going to send one’s tyre bill sky-high for the 10-in. diameter wheels are spinning frantically when power is applied to straighten the car out of an oversteer stance.

The extra torque shows up when taking acceleration figures too, the wheels spinning hard in 2nd gear as the gear-lever is whipped sharply back into that gear at just over 30 m.p.h. On paper the figures are not particularly impressive, 60 m.p.h. still occupying over 10 sec. (compared to 11, or thereabouts for the production model), whilst from rest to 90 m.p.h. will take 30.5 sec. using the gear speeds shown in the table. In top gear the acceleration compares favourably with much bigger-engined cars, 50-70 m.p.h. in 4th being recorded in 8.9 sec. For comparison we have established that the BMW 3-litre coupé accomplishes the same task in 7.5 sec., whilst the only comparable BL model in current production, the 1275 GT Clubman, needs marginally over 13 sec. for that top-gear speed increase.

All-out speed is not a strong feature of the Mini in its original form and it needs a lot of horses to pull the Issigonis creation over 100 m.p.h. Sparrow’s car could just nudge into the ove-100-m.p.h. bracket, but the engine was far, far, happier at an honest 85 to 90 m.p.h. It seems to the writer that it might be as well to forget about having a hotter camshaft in favour of a thorough balancing job, for the standard camshaft would suit the torque characteristics of the engine rather better.

The above remark does not mean that we suffered from the awful “wild cam splutter” in traffic, quite the contrary for third would pull the little car strongly forward from under 30 m.p.h. without so much as a hiccup from the oversize power unit. The water temperature never strayed far beyond the N-mark even in thick London traffic, but the oil pressure soon went down to 50 lb. if the engine was revved hard for any length of time.

So far as the Mk. 2 Mini itself goes we thought that the seats were their usual back-breaking selves and, though the interior looks a lot smarter, we found that the wind-up windows were not as effective in allowing the cool breeze one could enjoy in the earlier machines and those valuable storage bins are lost as well. Against those remarks one must face the fact that the runners of the old-style windows often become tatty after a few years, and ventilation can be very easily arranged when travelling solo in the later models by winding down the passenger’s window, thus avoiding a side blast of air.

Thus Sparrow achieved his object in having a speedy yet easy to drive Mini. The only improvement we would make to the car is to fit a numerically lower final drive than standard. This would be thoroughly worthwhile, reducing cruising noise levels, suiting the engine’s character and cutting oil consumption to a more reasonable figure than our thrashing of 200 m.p.p.! However, if you want the sort of neckbreaking 128 b.h.p. performance that the rally Mini enjoys, or any stage between, a trip to this rally driver’s garage at 2 Reddich Road, Studley, Warwickshire, should be well worth while.—J. W.

Performance
m.p.h. .. Sec.
0-30 .. 2.8
0-40 .. 4.7
0-50 .. 7.3
0-60 .. 10.5
0-70 .. 14.6
0-80 .. 20.9
0-90 .. 30.5

Gear speeds used:
First .. 32 m.p.h.
Second .. 52 m.p.h.
Third .. 74 m.p.h.
Fourth .. 101 m.p.h.
Standing 1/4-mile .. 17.9 sec.
Overall fuel consumption .. 23.7 m.p.g.

Converters: Will Sparrow Ltd., 2 Redditch Road, Studley, Warks.
Price: Engine, as described, £100.