F60S Engine timing

[Alastair Thomas]

We have been bedevilled by lack of power from the engine in our F60S LAAT.
It is true that the current engine fitted is the 85HP Dagenham engine but this does not explain why even the most modest inclines drop the speed to 12mph. Had we had a full complement of crew and ammunition, and if we had a Bofors attached, goodness knows what the performance would be like.
Having checked everything else and based on the fact that performance increases the more we advance the ignition, I am pretty sure that the engine rebuilders have mistimed the camshaft.
I see from the exploded diagrams that I can get access to the camshaft gear by removing a plate at the front of the engine but there are no timing marks that I am aware of external to the engine.
Is there an easy way of determining top dead centre on piston number 1 without removing the head?
Am I right that it would be possible to pull the camshaft timing gear off in situ so as to avoid pulling the camshaft forward (and ending up with a tangle of valves and cam lobes) and then retiming the shaft to the crank shaft?
Are there timing marks on the gears?
Regards,
Alastair
F60S LAAT
Lynx I MkIII*