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Competition Car Profile: Austin 7 (1922-1939)

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Whether for trials or racing, this is what goes into the vintage tiddler.

Made from 1922 to 1939, the Austin Seven has been proven by hundreds, probably thousands, of enthusiasts as the cheapest way into a vintage (pre-1930) car. A rolling chassis suitable for building up is typically £2500-3000 and could be completed for less than £10,000, though it’s possible to spend up to £30,000 – and original Ulsters can be bought more cheaply than that.

Chassis and body
Sevens use a simple two-rail, 75in-wheelbase chassis made of channel-section steel. There’s not much you can do here, though Steve Hodgson, who builds Sevens to all specifications, says: ‘Move the battery box from under the passenger seat, where it will get clouted on trials.’

Standard bodies have to be just that, though for modified trials and racing an Ulster replica type aluminium body is the norm, available from the likes of Roche for £2000-3000: ‘Factor in about another £1000 if you want wings and lights.’

Engine
In VSCC terms, there are two choices for trials cars: standard and modified. ‘Standard is what it says,’ explains Hodgson, ‘which means you have to have a two-bearing pre-1930 engine with standard rods and pistons and splash lubrication. It all wants to be crack tested and balanced, but you can assemble it yourself on the kitchen table.’

The Seven engine is a 747cc sidevalve ‘four’ whose two-bearing crankshaft is notoriously whippy, but various alternatives are available, with counterbalance weights. Lubrication as standard is by jet and splash – there is an oil pump, contrary to popular belief, and the system can be modified with a better pump to give full pressure lubrication: ‘It needs 50psi at 5000rpm,’ says Hodgson.

The maximum safe rev limit is 6000rpm and the limiting factor is the engine block, where it mounts to the aluminium crankcase. A new block is £850. At these revs you won’t be using the standard pistons and conrods, though Renault 4 items fit, and are available and relatively cheap. A Phoenix crank and rods will set you back about £1500: ‘The faster and more manic you go the more it costs,’ explains Hodgson.


A high-lift cam gives more torque, and a high-compression head helps, but it must use 18mm plugs to remain vintage. For racing, carburation is almost universally by a 1¼in SU, as found on Minis, Morris Minors and Midgets: ‘Some people use twin 11/8 SUs [early Midgets] which give a bit more top end.’ Supercharging puts the car into the 1100cc class, facing up to Anzani-engined Frazer Nashes: ‘Against which Sevens don’t stand a chance…’

Transmission
Three-speeds are standard fare (four-speeds did not arrive until 1932), and differentials are available in 5.622, 5.25 and 4.9:1. ‘The 4.9 is much too high for trials and even for racing the 5.25, as originally fitted to Rubys, is a good compromise,’ says Hodgson. LSDs are not allowed in VSCC trials, and scrutineers use rollers to make sure the rear wheels can turn independently. ‘You can use a lower first-gear ratio but most people use standard.’ The original fabric coupling between the propshaft and rear axle will cope, but not for long; changing to a Hardy Spicer U/J is preferable.

Suspension and wheels
Sevens use a transverse leaf spring at the front and a pair of cantilevered quarter-elliptics at the rear. The difference between a racing and a trials set-up is basically ride height and stiffness: ‘For racing you want the springs as flat and locked down as possible, and the dampers wound up,’ says Hodgson. ‘You can used a bowed front axle for a little negative camber. The original arrangement allows the front axle to “swing”, but for racing that can be eliminated with a short Panhard rod or triangular plate to stop the spring moving sideways. Wheel-wise, 18-inchers are the smallest you can use, so for trials we use those, with 19in fronts. Chen Sing makes a good, spongey, 4.00x18 tire for the back, but on the
front I like to use 3.50x19 Avon sidecar tires – the sharp edges cut through the mud better.’

Seven steering is super-direct, and Hodgson favours a 1930-’31-type cast-iron steering box, which is stronger than alloy. The later-type wheels are stronger, too – the originals have an ‘Austin’ script on them.

Brakes
Up until 1930 Sevens used two braking systems, the rear units operated by a pedal and the fronts operated by a handle. Even in the best possible condition they are pretty marginal, and the usual mod for racing is to couple the system so they all work together, but Hodgson offers a word of warning: ‘The operating arm hangs down, and if you clout it on a trial it pulls on the brakes and stops the car.’
 
He’s not a fan of hydraulics on a Seven, and they’re not vintage in any case; the best brakes to use are Girlings, which have a separate backplate and cable adjusters, plus cast-iron drums rather than earlier type pressed steel.

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