NOTE. - In normal service there should be no need to remove the camshaft, but in course of time the replacement of the cams may become necessary. The following directions explain how to remove the camshaft and the vertical bevel bush housing and bevel, but if it is required only to substitute a new cam for one which has become worn, it is better to leave the bevel bush housing in place and to take away the bevel housing, cam¬shaft, cams and bevel bush housing together, thus avoiding the necessity for re-meshing the bevel gears and re-making the joint between the bevel bush housing and the aluminium bevel housing. The procedure to be followed is therefore the same as detailed below except that the bevel bush housing remains undisturbed, and after removal of the small square cover from the left-hand side of the head, and the removal of the three nuts securing the bevel housing to the head the camshaft is tapped through the ballrace. Be careful, however, to replace any shims fitted between the small cover and the head or else the meshing of the bevels will be upset.
Proceed with the first part of the work as described on page 32 to remove valves, springs and rockers, etc. Next loosen and take off the two nuts securing the top vertical bevel pinion bush housing to the bevel housing and pull out the housing. It will save time when re-assembling if the number of joint washers between the face joint is noted, so that the same number of new ones may be used when re-fitting. Having removed the bush housing take out four screws and remove the square cover at the sparking plug side of the head - and, note carefully the number (if any) of metal packing shims used between the cover and head, as these determine the lateral location of the camshaft. Now undo the three nuts holding the bevel housing, one at the bottom below the square camshaft ball race cover and the other two at the two top corners of the flange behind the large part of the housing on the offside of the head. Pull the bevel housing away with the shaft and cams.
To withdraw the cam a special puller is needed, and in no circumstances must the shaft be pressed through the cam to remove it as this would damage the bevel housing. Unless special facilities are at hand this is a works job.
The parallel part of the camshaft upon which the cam is fitted is slightly larger in diameter than the part which bears in the camshaft bush in the bevel housing, so that if a new bush is needed the cam has first to be drawn off and the key removed, and then the housing and bush must be heated to approximately 100 degrees Centigrade to expand the bush and permit the camshaft to be pushed out through the bearing.
The bush is of aluminium alloy pressed into place, and if a new bush is fitted it must be located as shown in the appended sketch. The bush must also be oil grooved so that the groove overlaps the ground flat in the shaft - for which grooving the old bush may be used as a pattern or guide.
When fitting the cam note that the inlet cam goes on first and is nearer the right hand or bevel gear end of the shaft. To distinguish the inlet from the exhaust cam note the position of the keyway in relation to the cams. The "peak" of the inlet cam is almost exactly above the keyway. Press the cam into position, setting it finally exactly .4375-in. from the end of the camshaft. See adjacent sketch.