A MARSHALL SUPERCHARGED FORD
For ten years or more hopeful writers in the motor and lay press have proclaimed the coining of the supercharger. Its manifold advantages in the direction of improved carburetion and increase of power for a given engine capacity are common knowledge in the sports car world, but it is only quite lately that the ordinary motorist has realised that the blower can also be employed with great benefit on the family wagon.
The Ford Ten is well in advance of the ordinary touring car by reason of a powerful engine, with its sturdy three. bearing crankshaft and its lightweight of lb cwt. for a four-seater saloon, but it has no pretensions to be called a sports car. Last month, however, we tried one of these cars fitted with a Marshall supercharger and were much impressed by the big-car feeling brought about by a boost of only three pounds per square inch. The petrol consumption is about 33 m.p.g.
The car in question was bought second hand after it had covered 8,000 miles and had not yet had its valves ground in or had the carbon removed, SP its condition may well compare with that of the less carefully tended hack car. Compression ratio and ignition setting remained as standard, but using high-octane fuel such as Pratt’s Ethyl or Cleveland Discol, pinking was only faintly perceptible with full throttle at low engine speeds. The car got away in an impressive way either on top or in the gears, well silenced by the standard muffler. A faint sound from the straight pillions in the blower could be heard at low speeds, but silent-running helical gears are used on the latest superchargers. With an engine due for decarbonising, acceleration figures could not be expected to be at their best, but standing-start figures of ln seconds to 50 m.p.h. and 28 seconds to 60 m.p.h. give some idea of how the get-away has been improved by supercharging. There was a certain amount of clutch slip getting away with full throttle on low gear. This slip was not experienced when the car was driven normally and amid probably have been overcome by adjusting the clutch. The all-out speed when the car is in good trim is about 80 m.p.h. We reached 75 on a favourable slope without the car being taken to the limit, while it ran along very comfortably at 60. More important to the average owner probably than all-out speed was the improvement in hillclimbing. Gradients of 1 in 10, such as
the hill out of Rickmansworth towards Harrow, and the various. slopes leading to the top of Harrow Hill, could be climbed on top gear without rushing, starting at 30 m.p.h. and with this fine useful flow of power a willingness to pull slowly against the collar, a characteristic seldom found on small cars nowadays. The Ford Ten is fitted as standard with a down-draught Zenith carburetter. In the supercharged version a vertical induction pipe with a blow-off valve takes its place, with the supercharger and the original carburetter mounted above. An extended bracket on the supercharger brings the driving pulley in line with the crankshaft and dynamo pulleys, and a
rubber belt, tensioned by Swinging the dynamo, links all three. A minute quantity of oil is required for lubricating the supercharger and this is supplied from the engine, passing through a glassfronted drip feed with graduated regulating screw. Two questions are always asked in connection with a supercharged car, does it start easily and does it oil its plugs? During our test, which took place on a rarticularly cold day, starting was instan
taneous with no tendency to splutter, and the plugs, which were the type originally supplied with the car, were not in any way affected by idling or traffic work.
Including fitting, the Marshall installation for the Ford Ten costs £25, supercharge and oil pressure gauges being supplied as part of the outfit. Sets are also available for the P. and P.B. M.G. Midgets and the Magnette. The prices are respectively £29 and £33, and the blowers are mounted on the induction manifold which bolts directly onto the cylinder head. A double belt drive is used with a jockey pulley to adjust the tension. A similar arrangement is used on the installations for Augusta Lancias.