by D. N. WILCOXON (In an Interview)
However much motor-cars may vary in design, the same general principle applies to any sort of tuning which may be .performed On them. For a small sum Of money you can have a car brought to what might be called the best standard pitch of performance. Alternately, you can spend a substantial extra amount inti embody a numbcr ef alterations which make -all the difference if the machine is to appear in open competition. These two aspects are dealt with below as applied to the " 90 " and the " 105 " model Talbots. Incidentally it is worth recalling that the " 90 " differed from the " 75 " only by reason of the highcompression head, so anyone who has one of the later models can readily improve the performance to that of the sports model.
The term " Ninety " referred to the horse-power and not to the all-out speed of the car in question, the Maximum with open four-seater body varying bet weep 75 and 85 m.p.h. The engine is particularly sensitive to the ignition setting, and this is always the first point we check when seeking to improve the performance.
The Deleo distributor is fitted with two cams and two contact-breakers, each serving three cylinders. This arrangement halves the speed at which the breakers operate and ensures a regular spark at high revs., but it is essential that they should break at even intervals. This is not at all easy, to verify by normal methods. We keep a special apparatus for checking the adjustment The firing intervals can vary by as much as half-anitself on the flywheel, and in order to obtain maximum efficiency, gaps and firing intervals ought. to 1--,)e checked every thousand miles. The advance and retard is regulated by springs and balance-weights. The former tend to become weak in time and this gives advance too early and slows acceleration, while it is also necessary to make sure that the slot which regulates the amount of advance is of the correct length. 33 degrees of advance is allowed with the standard compression of 7.5 to 1, but only 27 is needed when running
on the high compression of 9 to 1. In this ease, of course, neat benzol must be used as the fuel. The carburetter does not need much alteration, though we have occasionally used jets larger than standard, with an improvement in performance and no appreciable increase in petrol consumption. On this model the fuel is supplied by an A. C. petrol pump and, as the result of high revs., the return spring heeotnes weak or even breaks. Misfiring
at high revs, then ensues anti, as the spring's only cost a few pence, it is worth vIjiie renewing them every 5,000 miles. The valve clearance is not critical, but the six-thousandths advised in the instruction book is insufficient if the car is to be run at any speed. Eight-thousandths for normal running is about right, and possibly, ten if continued high speeds are contemplated.
Champion R3 sparking plugs are fitted as standard, but some engines run much hotter than others, and in many cases the R12 type, which has a long body with the hexagon extending well clear of the plug recesses is to be preferred. Though these arc virtually racing plugs, they do is a seem to sont up in traffic, though they need occasional cleaning to ensure a ready start on a cold morning. to the " Nineties " which we used to race, they differed frOtn the standard cars only in having the higher compression of 9 to 1, running on pure bensol. \\h ;:t really gave us the extra pesformance was in fitting light-weight hOd 105. The cars complete turned the scale at '2:3 cwt, as against 29 of the St anduni cars
Now Os to the kind of car Which can be evolved from the " 90 " chassis. The chassis in question belonged to the old white single-seater which was driven by the Hon. Brian Lewis at Brooklands in 1931 and also in the 1930 500-miles Race by the same driver and the Earl Howe when it averaged 104 M.p.h. for the full distance. It is now the property of Mr. Hebeler, who also used to perform consistently on the team cars. The first step we took was to fit two horizontal S.U. carburetters in place of the vertical Zenith. This Was far from easy, as the steeringcolumn came just where the rear carburetter was intended to go. We overcame the snag lw reducing the height of the steeringbox column. Then it was found possible to evolve an efficient two-carburetter ntsnifold, with two U-shaped pipes joining in the centre to Supply the double centre port. Two S.U. petrol pumps are used to supply the fuel,
as this ensures a full head of petrol in the carburetters before the dynamotor is put into operation. Incidentally, much weight has been saved by fitting a small Young battery in place of the standard fitment. Though of ,ijuite small capacity, no trouble has been experienced in getting an easy start.
A Scintilla vertex is fitted in place of the coil-ignition system. The Delco system is pre-eminently reliable, but we have always found that magneto ignition gives that little extra power.
The compression has been raised to 8.5 to 1, but the car runs without a trace of pinking on Cleveland Discol. The high anti-knock value of the fuel partly accounts for this, but the better distribution which the two carburetters give is also an important factor.
In order to bring the appearance of the car into keeping with modern ideas and also incidentally to reduce the head resistance we fitted a special Serck radiator which is about eight inches lower than standard. Extra Cooling capacity is secured by having the film six inches deep. The springs are now straight instead of being cambered, and a neat two-seater body is fitted. The part of the chassis behind the rear spring mounting has been cut away, and a 23-gallon petrol tank fitted just in front of the rear axle. The weight distribution is no longer affected by the amount of fuel in the tank, and there is a useful amount of luggage space between the seats and behind the seats.
Special Holden and Hunt brake drums have been made for the car and Mr. Hebeler finds he can go for long periods without the need for adjustment.
With a 4 to 1 back-axle ratio and 5-inch tyres, it reaches its rev.-limit of 4,500 r.p.m. very easily, giving a speed of 93 m.p.h. and, with larger tyres, could easily be got to go at an even higher speed with a slight sacrifice of accelera
The car complete only weighs 23 cwt. so its performance is quite striking,
tion. At present, this is about equal to that of a V8 Ford ! The " 105 " responds to the same treatment as the smaller car, particularly in respect of the ignition. The carbure
tion calls for little change from standard, though here again larger jet and chokes are sometimes of advantage. A peculiar ity we have found is that often they do not develop their full power during the first 5,000 miles, the reason apparently being that the valves and seats take a good time to bed down. If the engine is taken down and the valves and seats tuned up with cutters, not ground-in in
the ordinary way, the car will then go on with greatly increased power and for a long period. Early " 105s " were fitted with rather a "slow", camshaft. On later ones the racing camshaft which provided considerable overlap was standardised. With the engine in good condition, the three-litre• engine will pull quite a high gear, and a standard saloon we prepared and fitted with 4 to 1 back axle lapped Brooklands at 86 m.p.h. with a maximum
The racing " 105s " differed from standard again, only in having the high compression and a light body, the car complete weighing 28 cwt. as against 32 of the standard sports job. In this trim they have lapped Brooklands at 113 m.p.h., while Brian Lewis's single-seater got round at 119.
This latter car Mr. Fox retained and fitted the chassis with a substantial touring saloon. In this condition the car did its ninety, running on petrol and 20 per cent. benzol. Here again we experimented with twin carburetters, and evolved an induction pipe on which we fitted two dtwn-draught S.U.s. Rather to our surprise, the car now runs perfectly smoothly on commercial benzol mixture, proving beyond doubt that better distribution is a powerful factor in preventing pinking. So much power was there, in fact, that besides the 4 to 1 back axle ratio, 6-inch rear tyres are fitted and the engine is only running at 3,800 r.p.m. at 90 m.p.h. Acceleration has not been sacrificed to obtain a high maximum, as may be gathered by the fact that Mr. Fox was able to average 60 m.p.h. for the 170 miles from Le Mans to Boulogne last year with four people up and a good load of luggage. As an instance of how well the cars wear if properly looked after, it is worth recording that this car has done 30,000 miles of strenuous work with the original pistons. Apart from a trace of bell-mouthing at the top of the bores, which does not affect the oil consumption or power, the cylinders are still in perfect condition. The 'secret of long life is TO Change the oil regularly every 2,000 miles, Nthile a graphite upper cylinder lubricant of about 92, which is not bad for a corn pletely equipped motor-car of this
has been found of advantage. Equally important, of course, is to warm the engine thoroughly before putting it under load. Two final points regarding the upkeep of Talbots. In the first place the dynamotor should be inspected regularly and carbon dust cleared away from the commutator and brushes. A motor of this type dissipated something like three electrical horse-power starting a stiff engine on a cold morning and, as the dynamotor does not have the advantage of a flywheel reduction gear, it is parti
cularly necessary to have everything in good trim.
The other component which sometimes calls for attention is the clutch. Behind the lining a series of leaf-springs are inserted, the idea being to force out the lining at a number of points. A little slip takes place, easing the engagement until the clutch plate is pushed fully into contact with the lining. If the clutch is inclined to snatch or shudder, it means that either the leaf-springs have gone flat or broken, or the clutch plate is no longer true and needs machining. An additional tip is to " massage " graphite into the lining with the tips of the fingers; this brings the final " velvet
touch " to the take-up. Strangely enough, the same expedient can often be used to overcome snatch on the bottom gear of the self-change boxes, the only difficulty in this case being to detect the exact place to insert the graphite. Apart from that, don't play with the selfchanger. It is an expert's job, and should only be entrusted to those who are thoroughly experienced in this direction.