The MG Story: The MG PA and MG PB

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The MG Story: The MG PA and MG PB



Cecil Kimber and his small team at Abingdon had a flair for designing, and producing cheaply, small, fast sports cars which caught the public imagination. "Kim" was so successful that even today, it could be argued that the MG is the world's best-known and best-liked sports car. There is something about the sparkling knock-offs, slab petrol tank, and swept wings of the classic MG which captures everyone's heart.

But MG's have always been noted more for what they can be made to do, with modifications, than for what they can do in standard form. The competition record of cars like the supercharged J4, the revolutionary RA single seater, the six-cylinder 1100cc K3, and the screaming Q-Type was not been beaten by any other marque at the time. The first six places in the Brooklands Double-Twelve, first and third in the Irish Grand Prix, first in the Ulster TT two years running, and a class win in the Mille Miglia were just a few MG successes. From 1931 MG's were the world's fastest class H cars.

But this all stopped in August, 1935, when Lord Nuffield broke Kimber's heart by selling the assets of MG to the Morris group, which placed a ban on all works racing. The PB - the last Midget to be powered by the almost legendary little high-revving OHC motor - ceased production a few months later. From late 1936 on, despite cries of anguish from Midget devotees, there followed a succession of mass-produced push-rod OHV cars based on long stroke, low-revving Morris engines. These had good low-speed torque and soon won a name in trials, but enthusiasts took a long time to accept the pushrod cars.


Despite some MG's being capable of revving out to over 8000 rpm, the engines had all only used two main bearings. Progress appeared in mid 1934 in the form of the MG PA, which featured three mains and continued the shaft-driven single overhead cam layout and standard Midget displacement of 847cc. With its sweeping clam-shell fenders the PA was truly a tiny TC, stretching 15 cm less between hubs than the latter. This was still a few centimetres more than the J­Types though, and the purists were disappointed when the PA was weighed in at 1650 pounds, some 44 kilograms more than its predecessor.

To many (2000 eventual buyers) this was a better-than-even exchange for a cockpit free from flying gravel and clumps of turf. For roughly the last half year before the overhead-cam MG's were discontinued in mid 1936, a PB model was available just like th PA, except for a bigger bore and a 939cc capacity. This really did justice to the car and made it one of the most fondly remembered small sports machines ever assembled, and explains why they are so highly prized by collectors today.


All OHC Midgets were powered by the Morris Minor derived 850cc motor, which owed its design to the World War 1 Hispano Suiza aero engine. Used in almost standard form in the 1929 M-Type, on the C-Type it got a crossflow head, and the PA was first with a centre main bearing in 1934. In the PB the motor was bored to its 60 mm maximum, giving 939cc. With its comparatively short 73 mm or 83 mm stroke, light and direct valve gear, ample bearing area, and great rigidity the little power-plant could take formidable stresses with amazing reliability.

The camshaft, driven by two sets of bevel gears via a vertically mounted dynamo armature shaft, operated two lines of valves, with stem tips inclined inwards, through light rockers. In its ultimate stage of development, blown at 28psi, the willing little Midget motor gave 113 bhp at 7200 rpm in the 750 cc Q-Type - 145 bhp per litre. Later, with a privately fitted twin-cam head, the same engine was bench tested to give nearly 160 bhp. The three-bearing Midget units were the only pre-war engines marketed with a guarantee to cover the use of a supercharger, provided no more than 6 lb boost was used. And after years of "automotive development", the output of a standard PB was equal to that of the then new MG Midget.

Motor Sport Monthly's Review

In its April, 1936 issue, the British monthly, Motor Sport, road tested a PB and had this to say about the last "cammy" Midget: "There are few more pleasant experiences than to be humming along in an open car on a fine day, and the Midget quickly settled down to a steady gait of 55 mph with inaudible exhaust and a smooth running engine. Nipping through Abingdon and out into the open country, third gear seemed adequate where second would have been required on the PA and there was quite a useful performance on top gear. We had been warned that this engine was not quite as smooth as on the production cars, but even so a feeling of power is not unwelcome on a sports car, and the one we tried felt as though it was taking pleasure in pushing the needle to higher speeds.

"The seat is raked to give an upright though restful driving position, the steering ratio has been raised so that only a slight movement of the wheel is called for on a thirty degree bend, and a useful castor action centres the steering as the rim is released. The steering is positive but remains light and this ease of control applies equally to the brakes, the clutch and the gear-change. 55 mph seems only a gentle amble on the Midget in spite of the engine turning over at 4000 rpm, but when a call comes for full speed ahead there is plenty in hand and the little car gets up to 60 and even 65 quite readily on short stretches of road. Where winding roads are encountered, of course, full use of the gearbox is needed for maximum performance, and the conveniently placed gear lever and light clutch give one every encouragement. The engine spins up promptly when changing down, a valuable feature when trying to maintain momentum on a trials hill."

Motor Sport said a maximum of nearly 60 mph was possible in third gear and commented if full use was made of this, the PB would hold its own with cars of much higher horsepower through being so handy and light to drive. The report commented further: "Tested over a flying half-mile, the Midget registered exactly 75 mph, a very useful speed for an unblown 9 hp car in touring trim. With the screen raised, 70 mph appeared about the maximum. The engine runs quite happily up to 5500 rpm, giving road speeds of 21, 36, 57 and 75 mph in the four gears."

Behind the Wheel

In 1936, the PB cost 222 sterling in England, but unfortunately it was not in production long before the OHC engine was superseded. Quite a few PB's found their way to Australia, but there not many survived. The non-independent suspension, stiff springs and direct steering, all contributed to safe and predictable handling, and the driver knew just what the car is going to do, and when. The engine would rev happily to 6000, and the exhaust note sounded like tearing linen over 3000. It took a strong foot to use the 12 in cable-operated brakes, but the PB really stopped, and you just couldn't fade them.

The gearbox with its straight cut first and second, and constant mesh third and top, was a delight. An extremely short clutch travel made compulsory double-declutching easy. Lack of a fan or water pump meant you had to keep the PB moving in hot weather, but it wouldn't overheat under normal conditions. A loud whine from first and second gears made pedestrians look up, but noise was one of the car's endearing features. The cam-drive was noisy too, but over 2000 rpm, the exhaust drowned most engine noises. The semi-gated gear change had a flick-up safety catch to block off reverse. Although the PB had a full length windscreen and a hood, we doubt few owners ever fitted them.

Also see: MG Heritage | MG Performance Chart | MG Car Reviews
1936 M.G, PB Midget
The last type of M.G. Midget to have an O.H.C. engine, the 1936 PB.
1934 M.G. P-Type Midget 847cc Engine
1934 O.H.C. 847cc M.G. P-Type Midget Engine.
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