The Radbourne 652-c.c. Fiat

Cheap, cheerful and economical modified motoring

LAMENTABLY, many motoring enthusiasts now feel that there is little joy left in driving under the restrictions of current legislation and cramped traffic conditions. This is a pity, for there are still ways of deriving satisfaction from a motor car without becoming ensnarled in a traffic hold-up or attracting the wrath of the law. One method of doing this is to use country roads wherever possible and to drive an innocent-looking saloon modified to give excellent acceleration and superior handling to the standard product, a subject on which we hope these pages can offer some help.

Recently we have driven a Fiat 500 (how innocent can you be?) modified by Radbourne to exceed this country’s overall speed limit and to provide the comparatively impecunious motorist with a superb town car or by-road express.

To provide the extra performance Radbourne have linked up with Nardi & Co. of Turin under an arrangement by which Nardi supply the parts while Radbourne fit and market them. Radbourne have considerable Fiat tuning and racing experience; in fact, two of the firm’s directors, John and Geoff Anstead, have raced homologated Abarth 850 saloons at club level British meetings. A third director speaks fluent Italian and he used to look after the buying of all Abarth equipment until this became too expensive for mass sale (though still available to special order) and he approached Nardi. Radbourne have another link with Italy in their agency for Weber carburetters and this business, combined with the sale of production Fiats, has given the company a suitable base on which to build a conversions organisation. Sales of all products except the Weber carburetters are dealt with from Clarendon Road in Holland Park, London, where there is a small workshop and showroom. The carburetters are handled at a nearby and far more spacious building in Fulham.

The basic ingredient in the Fiat 500 conversion is increased capacity, raised from 499 c.c. to 652 c.c. by larger bore cylinder barrels and pistons. The crankshaft dimensions are as standard, so the revised bore and stroke figures are 77 mm. by 70 mm. The wellknown air-cooled twin-cylinder engine is thus even more willing to rev than the standard unit. All the parts used in the “stretching” kit are new and there is no exchange scheme; even so, at £82 for parts or £100 fitted the kit offers reasonable value. Other changes included in the price include a beautifully cast and finned alloy sump holding seven pints instead of the standard five, a high-lift camshaft and a rejetted standard carburetter. Appropriate gaskets and a cast alloy rocker box finish the kit parts list. Peak horse-power is said to be 30 b.h.p. at 5,000 r.p.m., which is quite an improvement on the production peak of 21 b.h.p., though still only the amount that an American V8 wastes on supplying an air conditioning unit! Customers who are unsatisfied by this stage of tune can go further and buy more power, but the only extras fitted to the test car were a set of four-inch rim ventilated steel wheels costing £4 15s. each. Stiffened and lowered suspension can also be installed for £20.

Our demonstrator was finished in fashionable mustard yellow (the Fiat people call it “Positano”) and had a small label on the sides reading “Radbourne 650N”, which was probably a mistake as this conversion is offered both for the normal 500 (selling for £572 5s. 10d. and the 500 L, our car being the luxury I. model complete with sunroof and black interior. Logically, therefore, the label should read “NL”.

Starting any Fiat 500 for the first time is slightly disconcerting because both the choke and starter levers lie on the floor between the front seats, the starter sounding rather sluggish to an untrained ear. We were greeted by the fuel red warning light and the petrol gauge needle flicking up to the “E” mark. However, we found there was sufficient petrol remaining to cover seven miles, after which five gallons of Jet were needed to fill the tank. The larger pistons increase the compression ratio from 7 : 1 to 9.2 : 1 so premium four-star petrol is necessary, though not often as even driven flat out on a motorway the baby Topolino manages 42 m.p.g.

Having driven a standard 500 we did not expect much performance from the Radbourne car, even in its modified form. However, we and our doubting passengers were surprised at just how quickly one can travel from A to B. For example, London to Birmingham via the M1 took only five minutes longer than in a 100 m.p.h. saloon. precious seconds being saved by the Fiat’s modest size when slipping through traffic, assisted by the agile cornering.

As is the case with people who have strong characters, the Fiat’s bad points stand out strongly, especially in modified form. The gear ratios are unsatisfactory, first gear becoming almost redundant because of the extra torque. Interior noise border’s on the threshold of pain when attempting (successfully, according to the speedometer) to exceed our legal overall speed limit.

The gear-change is a matter of taste as the non-synchromesh operation gives great satisfaction when used properly, but can be annoying to those who have become used to all synchronised boxes or who have not had the benefit of a few years spent tackling “crash” or motorcycle gear-changes. Unfortunately the car jammed in third during the test and this did not endear the memory of its gear change, although it did prove how flexible the engine is, for the car was driven back into London with very little difficulty. Radbourne have had some difficulty in carburation with the N and we found the motor cutting out at an indicated 20 m.p.h. in first, 30 in second and 51 m.p.h. in third. On long downhill stretches the speedometer would indicate just 80 m.p.h.

Although we were unable to take any accurate performance figures the Radbourne people claim that the 650 N will reach an honest 70 and accelerate at a similar rate to the production 848 c.c. Mini, this seems about right to us.

Breaking for those with large feet can be a trifle tricky because the pedal is at an awkward angle, but once the knack is mastered the all drum system is quite able to cope with the extra performance. Michelin ZX tyres were fitted and on damp or greasy roads the driver needs to be fairly adept at catching the tail-swing when rapidly negotiating a roundabout or similar curved slime traps. However, this remark does reflect the rate at which the car was driven nobody seems capable of conducting it slowly, our normal main-road gait being between 60-65 m.p.h. depending on wind and gradients. All speed is relative and the author feels that most readers would find the urge to exceed the blanket speed limit diminished by the feeling that one is rather bigger than the car, so that in the event of a crash it is going to hurt!

With a quickly operated and leakproof sunroof, parsimonious ways and enjoyable handling plus a generous power boost compared with a standard 500 this latest Radbourne project should sell very well indeed.—J.W.

Converters: Radbourne, 1a Clarendon Road, Holland Park Avenue, London, W11. Price as tested £639 (Standard Mini Super De Luxe C074). Overall fuel economy: 45.1 m.p.g.