|Tuning the sports Austin Twenty
Some details of the methods employed to obtain
extra speed for racing
By Felix Sciven
From the outset I wish to make plain that the car of which I am writing,
although exceptionally fast, is made up of standard touring model parts.
In order to allow any engine to deliver the utmost power, however, in
general refining process of small details has to be undertaken., and
this, in the main, is what I have done. For example, in the beginning
the standard connecting rods and pistons were most carefully balanced
by means of filing and scraping, each unit was brought to exactly the
same weight as its fellows. A copper induction pipe of rather bigger
bore and easier sweep was made to replace the standard induction pipe
of aluminium, and a larger size Claudell-Hobson carburetter was fitted.
The opening and closing of the valves remains just the same as in the
standard touring car, but there is sufficient “ nose” on the cam to
give a slightly higher lift of the valve itself, while, to make the
tappets follow the contour of the cam more closely, stronger valve springs
Initial Tests and Speed
At first I took the car with a rough test body containing one or two
sandbags on to the track at Brooklands, and tried it at speed. The engine
proved to be a very willing one, and after first of all trying various
grades of spirit, I selected Aviation as giving the best all-round results.
Although the rough test body and dash were the very reverse of streamline
shape, I was able, after minor adjustments to carburetter, tappet clearance,
etc, to lap at approximately 75 MPH. I have found that the best clearance
between the end of the valve stem and adjustable tappet to be six-thousandths
of an inch, and the main jet that I have selected in the Claudel carburtetter,
when running on Aviation spirit , is one hundred and twenty five
The ordinary extra air control, as fitted to the standard model, is
also utilized, and has proved to be extremely useful even for racing
purposes, for after a lap has been covered and the engine really warm
to its work, a fair amount of extra air can be given to advantage. I
find that on my car no fan is needed on Brooklands, as the natural draught
created when running all out, which is in the neighbourhood of 80 MPH,
is amply sufficient to cool the radiator. Incidentally, Castrol R engine
oil appreciably increased my speed when used instead of ordinary touring
The Running Improving
From preliminary tests on Brooklands I was satisfied that the car had
distinct possibilities, but I had a outer jacket put round the T portion
of the copper inlet, as I found that the inlet pipe , owing to the evaporation
of petrol, became stone cold when the car was in motion, and this state
of affairs did not lend itself to good acceleration.
To all intents and purposes, I have left well alone and the seal which
the Brooklands authorities put around the engine and attached to the
frame after verification of cylinder bore and stroke, etc, remains still
intact., the car however has gradually become faster as is parts have
become run in.
One of the earlier difficulties which presented itself was that of getting
the car to hold on the road. This was done by the fitting both rear
and front Derihon shock absorbers, and by selecting rather weaker spring
leaves for the rear suspension, as with a two seater body these latter
had rather too much camber in them. In addition, the springs were core-bound.
This makes the springs stiffer and rather less comfortable over really
bad surfaces at low speeds, but for high speeds it is absolutely right,
and as a test I have found that both hands can easily be removed from
the steering wheel at 70 MPH.. The fitting of a sports body of a shape
more nearly approaching to the steamline renders the car much more comfortable
to ride in at high speeds, for with the ungainly test body the wind
pressures and eddies while going down the Railway straight in the teeth
of half a gale had to be felt to be believed.
Furthermore the streamline body which was fitted, increased the speed
of the car by fully 5MPH beyond that attained with the rough test body.
I have since carried out one or two little ideas in a way of streamlining
axles and dumb irons, all of which contribute to pace and I was told
that at the Whitsun Meeting, I have been clocked to cover a lap at 87
MPH.( I hope Mr. Ebblewhite will not read this, although I do not suppose
he has missed much in this direction that will serve to aid him in fixing
Although I have found this sporting model of the Austin “ Twenty” car
an ideal fast touring machine, out of which one can extract a great
deal of fun in competitions.