Marshall-Nordec Supercharger Installation

Details on this Rootes-type s/c circa 1959/1960

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This leaflet accompanied a letter sent out in March 1959, after an enquiry about a supercharger for a small Austin. I've reproduced the information from this single sheet on this page below, the diagram above being taken from this leaflet and enlarged as a point of reference for anyone restoring an old engine with this type of supercharger fitted to it.

Marshall Nordec supercharger information sheet

"The Marshall-Nordec Low-Pressure Supercharger Installation has been designed and produced particularly for use on the standard popular car of medium horsepower. It is precision built throughout and embodies all the latest improvements arising from over 20 years development.

The illustration above, shows details of the compressor and drive assembly. All installations incorporate the famous Marshall Rootes type compressor which is available in a complete range of sizes to deal with the requirements of engines from 750cc to 4,000cc. For 1 to 1.5 litre engines, a J75 model is used. This has a nominal displacement of 75 cu. ft. of free air per minute at a speed of 3000 RPM, and when driven at approximately 1.3/1 engine speed produces upto 6 lbs PSI boost pressure.

The compressor is built of light alloy castings and has two twin-lobed rotors which are driven through specially hardened gears. These rotors made of light alloy, are of involute form and are cut directly on to high tensile steel shafts and dynamically balanced after machining. The drive for the compressor is enclosed in a nosepiece casting which is extended forward to a convenient point to accomodate the front drive pulley. Enclosed in the nosepiece is a shaft mounted and running on bearings, and a simple coupling device. On standard installations a single driving belt from crankshaft pulley to supercharger is used.

"This precision built unit forms the basis of all Marshall-Nordec installations, also included are the necessary inlet and outlet manifolds, fixing brackets, crankshaft and jockey pulleys, lubrication arrangements etc. These parts are designed for each individual car and can normally be fitted without alteration to the standard engine unit.

"The installation will operate satisfactorily with any carburettor of suitable capacity, the original standard carburettor is usually employed with jet modifications. The oiling arrangements to the supercharger are entirely automatic. A tapping from the engine oil pressure pipe is delivered to the supercharger through an adjustable oil sight-feed and the oil after circulating through the gears and bearings returns to the sump via gravity drain pipe.

"Installations are supplied in kit form, and include all the parts necessary to install the equipment. A full size drawing with all parts clearly marked is included with detailed fitting instructions, and enables fitting to be undertaken by any reasonably competent mechanic. The only maintenance required is periodic adjustment of the jockey pulley to ensure the correct drive belt tension, and inspection of the oil adjuster to ensure that oil is supplied to the supercharger. Except for these two points the installation will operate efficiently for long periods without attention.

"The popularity of Marshall-Nordec installations is undoubtably due to the simplicity in design of the Marshall 'Rootes' type compressor which provides the highest degree of efficiency with maximum durability, so enabling the supercharger to invariably outlast the life of the engine to which it is fitted. A combination not normally obtained with other types of supercharger."

On the rear of the leaflet are several comments from owners who have this tuning mod fitted to their own car. Comments given include:

"I must tell you that since supercharging my MG I find myself driving a new car. Your statement 'this will pep up the TD quite a bit' is very definitely an understatement..."

"There is no doubt your supercharger does all that is claimed for it ... acceleration and hill climbing of the car is a real joy to anyone who is driving."

"This supercharger was bought from you two and half years ago, and during 20,000 miles has given every satisfaction ... after the above mileage the car only uses one pint of oil every 250 miles, and incredible as it may seem in this hilly district, it uses much less petrol than when unsupercharged ..."

How many cars still survive today with this type of s/c still in place I wonder??

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

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