100- 4 1953-55

Classics Monthly - - Marque Guide -

Pro­duc­tion of the Austin-Healey 100, des­ig­nated the BN1 series, started at Longbridge in May 1953. A four-cylin­der 2660cc en­gine sim­i­lar to the one fit­ted in the Austin A90 At­lantic pow­ered the new Healey and drove the 100’s live rear axle through what had started out in life as an A70/90 four-speed gear­box. Only three of the four for­ward gears were ‘live’ in the ver­sion fit­ted to the BN1; the se­lec­tor on first gear be­ing omit­ted due to the ra­tio be­ing deemed too low for a pow­er­ful sports car. Orig­i­nally de­signed for col­umn change, the ‘box’s se­lec­tors were sit­u­ated to one side, re­sult­ing in the 100’s floor gearchange be­ing an­gled to exit the left-hand side of the trans­mis­sion tunnel.

The 100’s chas­sis was a very ad­vanced struc­ture for the time; the main mem­bers con­sisted of two rec­tan­gu­lar boxes braced cen­trally by a cru­ci­form struc­ture. Mount­ings on the end of a pair of front trans­verse cross­mem­bers in­cor­po­rated fix­ings for the front dampers. Four body-mounted out­rig­gers were welded in pairs each side of the chas­sis’ main mem­bers, while at the rear sub­stan­tial cross­pieces con­nected a pair of body mount­ing legs. The 100- 4’s im­mensely strong and rigid chas­sis/frame set up re­mained largely un­changed through­out the big Healey’s pro­duc­tion run.

Al­though pre-pro­duc­tion 100 bod­ies were made of alu­minium, once BN1 pro­duc­tion moved to Longbridge the car’s wings and doors were changed to steel press­ings pro­duced by Jensen Mo­tors. How­ever, a small num­ber of early Longbridge-built Healey 100- 4’s re­tained pre-pro­duc­tion alu­minium bon­nets and boot lids, al­though all ver­sions were fit­ted with al­loy front and rear shrouds.

BMC in­tro­duced the BN2 Austin-Healey 100 in 1955 and al­though the re­vised sports car still re­tained the ear­lier car’s four-cylin­der en­gine and twin SU car­bu­ret­tor set up, the 100- 4 now was equipped with a stronger, fully func­tion­ing four-speed gear­box. De­spite the ‘box still be­ing de­signed for col­umn-change, the gear lever now ex­ited the trans­mis­sion tunnel al­most cen­trally and the re­vised gearshift was now a con­ven­tional four-shift pat­tern.

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