Comparisons- a dissection of a 1923 Model by Bill Sheehan
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COMPARISONS - a dissection of a 1923 Model.


Much is made of the great interchangeability of components within the various models of Austin Sevens. But many parts, although they may be capable of being swapped around, are quite different when it comes to making your car "as original". If we take say a mid-

1923 model compared to a 1927 model, here are just a few of the differences in the relevant parts.

Starting at the front, the crankhandle is two piece, the handle cottered to the shaft, whereas the '27 handle is one piece.

Crankcase & Block - the early crankcases are quickly recognizable by the Austin symbol being cast in a different place on the outside. The block had gone to the 56mm bore, but the tappet plungers for a while continued to be of the mushroom-headed type, quite different from the familiar straight-sided plungers. Obviously the brass tappet guides were a different shape to suit. The gudgeon pins altered and early on the cylinder heads were fitted with priming cocks.


Timing gear cover - Because the camshaft on the earlier car had no locating shoulder for the front bushing, it was necessary to adjust end float from the exterior - and provision for this is located on the front of the cover.


Sump strainer - the familiar flat meshed frame did not appear in the earlier model. Instead, a dished sheet-metal plate had three wells along its length, each well having a solid bottom but meshed sides.

These early cars had no speedometer, no fan, for a while no choke flap on the carburetter, no starter motor (the clutch chamber had a two-piece cover on its top), the flywheel had no chamfer (no need for ring-gear clearance before starter motors were

fitted), the gearbox filler was located on the front of the top cover (once starter motors were fitted they covered the filler hole so it was necessary to relocate & recast towards the rear of the lid).


Petrol tanks had the outlet tap located directly over the exhaust pipe, so this tap was moved on later models. The early tanks had no mounting lugs at the rear, the tank being located by its rear sitting on the instrument board lip and fastened to it by a long brass strap which ran over the top rear and down each side.


The rear of the gearbox did not have the familiar flexible disc, but a Hookes joint on the end of the output shaft. This was located to a Hookes joint on the end of the tail shaft by a slotted ball acting as a universal joint and enclosed by a two-piece brass housing.


CAV electrics featured in the early days, from a shorter generator housing, to the instrument panel with ammeter, to an aluminium-covered cut-out, to head and tail lights. The horn button was located on the instrument panel, not the steering wheel, the horn itself was a small Benjamin, not a large Rist and the magneto changed from a Scintilla to a BLIC.


The chassis rails had no upturn lip on the top-hat flanges, had no brackets for shock absorbers at the rear, had a simpler nose-piece casting with again no provision for mounting dampers, had only two holes to attach the one-piece "cows horns"; also

instead of the triangular riveted backing plate on the front radius-arm ball mounting, it just had the ball backed by a threaded stud which went through the cross member & was held by a washer and nut. The front cross member had no inboard supporting brackets

for the floor.

The front axle had no bosses or holes to mount a damper, had no tin dust shields, had no casting for grease nipples at the kingpins - instead it had a fitting with a Bennett's oiler to lubricate the swivel pins. The important difference was the stub axles being tapered so that tapered bore wheel bearings were necessary.


The rear axles similarly had no dust shields, had tapered bore bearings, also the c w& p housing had strengthening flutes running from the central drum to the axle trousers - three each side.


Wheels front and rear had 6" brake drums. Over the years Austin Seven brake levers lengthened, but the '23 ones are even shorter than the short 1927 levers!

In summary, it's more a matter of what was not there as much as what was different or swappable.




Bill Sheehan.