Speedwell BMC Engine Conversions.

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This leaflet, issued by Speedwell Performance Conversions Ltd, dates to the late 1950s, and features some of the engine tuning parts that were available to owners of BMC-engined cars of the 50s and 60s. It concentrates on A Series powered cars, such as the Austin A35, in the days before the Mini of course, which would go on to be another popular choice for the budding tuner.

Elsewhere in this section, details of Speedwell's other products - such as their performance exhausts and suspension conversions are outlined, along with complete kits of parts to uprate certain cars, such as the Austin A40 and A55 Cambridge, again popular BMC models of the late 1950s.

The cover of the fold-out leaflet shown alongside features a tuned A Series engine, fitted to an A35. Immediately obvious is the brace of twin SU carburettors fitted to special inlet manifolds, with balance pipe. Less obvious is the set of KLG spark plugs fitted to this engine, another piece of the Speedwell conversion kit. The rocker cover was also plated, instead of the usual painted green finish found on production A35s.

Inside the first page Speedwell outline the benefits that fitting their engine parts can bring, highlighting the fact that whilst production engines are produced to fine tolerances, they are at best a compromise, and to extract better performance and efficiency from a given engine, tuning parts, such as those offered by Speedwell, will be required.

"Basically, a redesigned cylinder head is fitted, which has been carefully developed with dynamometer and flow rig testing. The whole kit has been tested by many thousands of miles of actual participation in International races and rallies, and every stage of its development has been carefully checked and analysed to ensure that the power increase is allied with smooth and quiet running, easy maintenance and petrol economy. During the two years of competition proving, we have had no single case of part failure, and, as a result, we can confidently guarantee every component of the conversion for twelve months."

"What increase in performance can be expected?"

"All the figures quoted below have been obtained by independent motoring journalists on road test. In this way there can be no false impressions through the use of highly tuned demonstration cars, and the increases given are those which can genuinely be expected from a converted car."

Top speed. The increase in maximum speed as road tested is between 12 and 15 miles per hour for the entire range.

Acceleration. This is where the increase in performance is most apparent, and the average improvement of the various models is over thirty per cent. On the Austin A35, the time taken to reach 60mph is actually halved, and on the MGA the improvement is over 20 per cent.

Flexibility. The power increase in the lower and middle ranges has been commented upon very favourably by every motoring paper that has tested the cars. There is a substantial improvement in top gear acceleration which enables the converted car to be driven in a higher gear than would normally be the case. The saving of fuel and engine wear through the lower revolutions of the engine stresses the economy aspect of Speedwell Converted cars.

Acceleration performance data. (Austin A35)
0-30 mph (5.5 sec)
0-40 mph (7.5 sec)
0-50 mph (10.5 sec)
0-60 mph (15.0 sec)
0-70 mph (23.2 sec)

Maximum speed in gears.
1st gear: 20 mph
2nd gear: 40 mph
3rd gear: 60 mph
Top gear: 88 mph

Petrol consumption.
Hard driving: 34 mpg.

"What does a Conversion consist of?"

Speedwell flowed cylinder head assembled with special valves and springs.
Speedwell inlet manifolds and balance pipe.
KLG wide heat range sparking plugs.
Exhaust centre port casting.
Matched pair of SU carburettors with rubber mounted float chambers.
Plated rocker cover.
Gasket set.
Molybdenum disulphide oil additive.
Carburettor and exhaust gaskets, studs, nuts and bolts. Speedwell chrome flash.
Petrol pipes and unions.
Optional equipment - re-calibrated speedometer.

"The main item is the gas-flowed cylinder head, with its fully re-designed porting and combustion chamber shapes. It is supplied complete with valves and springs to Speedwell design and specification. These latter are paraffin tested before despatch and delivered ready assembled, with numbered valves carefully lapped to their seats. This unit is supplied on an exchanged basis (in the United Kingdom only).

Specially designed inlet manifolds are positively located to ensure perfect alignment, and a matched pair of SU carburettors, complete with all linkages and fuel lines, is provided.

Sparking plugs with a wide heat range are included, enabling the engine to run smoothly under both idling or sustained high speed conditions.

The compression ratio is suited for PREMIUM GRADES of fuel, and the exhaust manifold is modified to permit full exhaust gas flow. A straight-through silencer is incorporated to reduce exhaust valve temperatures.

Kits of parts are complete in every respect, there being no annoying 'extras'. An attractive "Speedwell" chrome flash is included for fitting to the boot of the car."

Price List.

Prices for the Speedwell engine conversions started at 45 GBP (with an extra 5 payable for fitting), this kit - numbered B.1000 - was designed for the Turner sports car, fitted with the 948cc A35 engine. Next in price, at 50 for the kit, was a setup for an engine not yet mentioned, the 1500cc B Series, as fitted at the time to the MGA, MG Magnette ZB, and the Riley 1.5. Option kit A.1000 was tailored to fit the Austin A35, Morris Minor 1000 and the Healey Sprite. This cost 65 for all the parts. Priciest of all options was the kit designed to fit the Wolseley 1500, Austin A55, Nash Metropolitan and the Morris Oxford Series of 1958, coming in at 80 all in.

Kits could be ordered either with or without the twin SUs, presumably allowing the owner-tuner to fit their own carbs, and this explains some of the variations between the kit prices for the A and B Series engined cars listed above.

What the Press said.

Needless to say, the press quotes given are very enthusiastic about the Speedwell-tuned cars that they had tested. John Bolster, summed up the Speedwell A35 as ".. a performance that can only be described as miraculous ..". Ronald Barker, of Autocar magazine, was equally keen: "A ready made potential rally or race winner, with qualities of performance, roadability, compactness and fuel economy which many more humdrum motorists would appreciate".

The Speedwell Electronic Rev Counter.

Any self-respecting engine tuner would be keen to keep an eye on the condition of this tweaked engine. Gauges for monitoring the oil temperature, oil pressure, and charging system were seen as essentials, and the really keen would also opt for a tachometer, or rev counter, too. Speedwell could offer the perfect tacho, an all-electronic gauge that ".. dispenses with the need for the out-dated drive gear and fitting charges, only three wires need to be connected". The Speedwell rev counter read from 0 - 8000 rpm, so perfect for high-revving race engines. The gauge was a joint production:

"Speedwell engineers have developed and manufactured the electronic part of the unit, while the rest of the unit is made by Sangamo Weston ... Most speed shops and specialist garages will supply the Speedwell unit or they can be purchased direct from Speedwell. Four- or six-cylinder models are available and for the most price of �18, and a few minutes fitting, you will have a highly accurate and fully guaranteed electronic instrument, which can be transferred from car to car".

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Old Classic Car (C) R. Jones 2023. Content not to be reproduced elsewhere.

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