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This packing plate is introduced to give an increased clearance between the starting dog (on the
crankshaft pulley) and the steering-rack housing.
The modification can be fitted to chassis prior to the one given above.
A.38 MODIFIED HALF-SPEED SHAFT AND OIL PUMP DRIVING SPINDLE
In cases of excessive wear on the oil pump driving spindle and half-speed shaft skew gearing, a
modified shaft (Part No. AEH619) and spindle (Part No. AEH620) may be fitted. The number of teeth
on the oil pump driving spindle has been increased from 10 to 11 and on the half-speed shaft from 9
to 10.
This modification was incorporated from Engine No. 315 and on Engine No. 313. The new
components can be fitted on earlier engines if they are both fitted at the same time.
A.39 MODIFIED PISTONS AND RINGS
To improve oil consumption, twin-segment scraper rings (Part No. AEH615) were introduced at
Engine No. 446 and twin-segment scraper rings fitted with expander rings (Part No. AEH672) at
Engine No. 2057. These rings are interchangeable with the micro-land scraper rings previously fitted.
To overcome any tendency to piston noise, piston assemblies (Part No. AEH640) incorporating new
top rings (Part No. AEH649) were fitted at Engine No. 606.
Piston assemblies, complete with twin-scraper rings, expander rings, and the new top rings, are
available under Part No. AEH673 and may be interchanged in sets of four with those originally fitted.
A.40 MODIFIED CRANKCASE BREATHER PIPE
A new crankcase breather pipe was introduced at Engine No. 657. The purpose of this modification is
to overcome any possibility of oil leakage from the engine breather onto the exhaust system, thus
causing fumes to enter the car.
Fitting the modified breather pipe (Part No. AEH628) necessitates the use of a new clip (Part No.
1G1309) and a longer clutch bell housing bolt (Part No. HBZ0511) in substitution for the clip and bolt
which previously secured the original breather pipe to the crankcase.
Fit the breather pipe to the vent pipe on the engine rear side cover, slide the clip over the end of the
pipe, fasten the clip to the gearbox mounting plate with the longer bolt specified, and secure with the
existing nut and spring washer.
A.41 MODIFIED TAPPETS
To increase the tappet contact area with the cylinder head and eliminate the possibility of tappet
fracture the length of the tappets has been increased by 25 in. (-635 mm.) to 1.5 in. (38-1 mm.).
This modification was introduced at Engine No. 1087. The new tappets (Part No. AEH651) may be
fitted to earlier engines in complete sets of eight.
Commencing at Engine No. 1587, tappet bushes have been fitted to the cylinder head to reduce
tappet wear to a minimum. Each bush is locked in the head with a screwed plug
A.42 MODIFIED TIMING COVER GASKET
To obviate complete dismantling of the timing gear each time a new timing cover gasket is fitted, a
gasket that is partially cut to provide four sections has been produced under Part No. AEH377.
The gasket may be fitted in the same way as the previous gasket, or alternatively any one or more of
the four sections may be detached and used separately.
A.43 ALTERNATIVE PISTONS
A domed-top piston giving a compression ratio of 83: has been introduced for standard use, the piston
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