Rephased Camshaft

Looking at the camshaft you will see a keyway on the bearing mount and a slot near the cam sprocket and a hole were the pin goes for the advance retard mechanism. All these marks are for alignment of the cam and the manual tells you to install the cam with these marks in the vertical position. There is also a drill mark on the sprocket and this is meant to be aligned with the top surface of the head. When the “T” mark on the crank is aligned and all these other marks are in position then the cam chain can be connected and the cam timing will be set.

All this is true for the standard engine and it will be in the correct position for the right cylinder to fire at TDC on compression. But in our engine the right cylinder has been rephased and fires 270° after the left and not 360°. So will this installation procedure still be true for our rephased engine?

Yes it will, because even though the right cylinder has been rephased and when the crank is at the “T” mark and it appears as though the cam lobes for the right cylinder are not in the correct position, if we rotate the crank 360° it will be correct for the left cylinder, and because we are altering the ignition and the cam for the rephase if you rotate the crank a further 270° hey presto the cam lobes for the right cylinder are now in the correct position. The fact is, it’s only the mark on the rotor that is incorrect for the right cylinder when it’s at Top Dead Centre.

So remember, the original timing marks on the alternator rotor are only correct for the left cylinder in the rephased engine but it does not effect the camshaft installation procedure in the manual.

In fact it might be prudent to put another timing mark on the alternator rotor for the right cylinder which would be placed 90° before (anti-clockwise) or 270° after (clockwise) the original mark. This would allow you to check the timing for each cylinder with a timing light on the original timing marks on the alternator stator with the engine running and also to indicate TDC for each cylinder. You could also paint the marks on the rotor different colours to indicate left and right cylinders.

So the original timing mark would now indicate the left cylinder and the new timing mark would indicate the rephased right.
I hope this has served to clarify the cam installation procedure and not cloud the issue as it is intended only as guide to those who may have trouble understanding the relationship between crank ,cam and ignition in the rephased engine.

Only degrees of crankshaft rotation are mentioned in the text.