[wilf leek]

Gerry - is the engine REALLY at TDC when the pointer and the marks on the crank damper say so?

Is it a rubber bonded type damper? Could the outer rim have spun on the rubber?

Probably worth checking the real TDC position using a bolt down the No 1 spark plug hole. Then you can at least eliminate incorrect timing.

Also, do you have an MSD ignition? They can sometimes give spurious results with some timing lights.

HTH