The J1 was the four-seat car in the range. The engine was the 847 cc unit previously seen in the C-type with twin SU carburetors giving 36 bhp. The car cost £220 in open and £225 in Salonette form.
The J2 was the commonest car in the range and was a road-going two-seater. Early cars had cycle wings, but these were replaced in 1933 by the full-length type that was typical of all sports MGs until the 1950s TF. The top speed of a standard car was 65 mph (105 km/h), but a specially prepared one tested by The Autocar magazine reached 82 mph (132 km/h). The car cost £199.
There were a few serious failings of the J2, most seriously that it only had a two-bearing crank shaft which can break if over-revved. The overhead-camshaft is driven by a vertical shaft through bevel gears, a shaft which also forms the armature of the dynamo. Thus any oil leak from the cambox seal goes into the dynamo brushgear, presenting a fire hazard.
Another problem was that it was not fitted with hydraulic brakes, but had Bowden cables to each drum. These require no more pedal force than any other non-power-assisted drum brake, provided that they are well maintained. The drums themselves are small and even in period it was a common modification to replaced them with larger drums from later models.
The non-syncromesh gearbox takes some getting used to, as for any car of this period, but with its short gear stick it becomes second nature to double de-clutch and rare to grind the gears.
The J3 was a racing version with the engine capacity reduced to 746 cc by shortening the stroke from 83 to 73 mm and fitted with a Powerplus supercharger. The smaller engine capacity was to allow the car to compete in 750 cc class racing events. Larger brakes from the L-type were fitted.
The J4 was a pure racing version with light-weight body work and the J3 engine, but using more boost from the supercharger to obtain 72 bhp.
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