Mods and Con­se­quences

Austin Seven

Classic Car Weekly (UK) - - This Week -

Colin Chap­man founded a whole sports car com­pany us­ing an Austin Seven as his start point, so there’s no short­age of po­ten­tial with this bril­liant pre-war peo­ple’s car. Re­ally, your op­tions are only limited by your imag­i­na­tion and bud­get.

All Sev­ens fea­tured a 747cc side­valve engine, apart from the first 100, which had a 696cc unit. Un­til 1936 there were just two main bear­ings fit­ted (one at each end of the crank­shaft), while later cars had an ex­tra one – but any Seven crank can break be­cause of flex­ing. The big end jour­nals were also in­creased from 1⅛in to 15/ dur­ing 1930, but even the larger items can fail af­ter years of hard use.

There are all sorts of things you can do with the engine, in­clud­ing fit­ting a stronger crank­shaft, sportier camshaft and slip­per pis­tons so you can in­crease the rev limit. The best crankshafts are made by Phoenix, avail­able through A7 Com­po­nents; these use mod­ern ma­te­ri­als and are much more durable than the orig­i­nals.

Chang­ing from a low-com­pres­sion to a high com­pres­sion cylin­der head is an easy swap and im­proves things no­tice­ably, while alu­minium heads are avail­able, which pep things up a bit more. When it comes to fu­elling, a sin­gle 1⅛in SU is fine for nor­mal use while a 1 in unit pro­duces a bit of ex­tra power. If you’re rac­ing you can go up to a 1 in SU but don’t bother with twin carbs as they don’t pro­duce any ben­e­fit over a cor­rectly set up sin­gle carb; it’s not un­usual for a carb to be taken off a Mini or Mi­nor without the nee­dle be­ing re­placed. The re­sult is an engine that will run fine, but will over-fuel con­stantly, wash­ing the bores.

There are nu­mer­ous op­tions when it comes to up­rat­ing the ca­ble-op­er­ated, sin­gle-lead­ing shoe brakes, de­pend­ing on the car’s age, in­clud­ing con­vert­ing to a hy­draulic sys­tem. But the lim­it­ing fac­tor is usu­ally the grip af­forded by the tyres, so be­fore you spend a for­tune on bet­ter an­chors make sure it’s go­ing to be of some ben­e­fit. Up­graded brakes are ad­vis­able be­cause the orig­i­nal sys­tem is so poor. You can con­vert to hy­draulic us­ing parts from the early Mor­ris Mi­nor 1000. It’s an ef­fec­tive swap but not a five-minute job be­cause you’ll have to fit a master cylin­der, new brake pedal, hy­draulic pip­ing and flex­i­ble hoses – along with the back plates, which are get­ting hard to find. Ox­ford­shire Sev­ens has de­vel­oped a twin-lead­ing shoe sys­tem that re­tains the orig­i­nal com­po­nents, is highly ef­fec­tive, yet re­tains the ca­ble sys­tem so it’s much cheaper and eas­ier to fit.

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