Have you checked the timing mark is correct, i.e. the marked TDC is actually TDC. I have seen V8s showing TDC at 8 - 10 degrees out. This is how I did it - Sparky's winter/spring/summer/autumn work
Have you checked the vacuum unit on the dizzy ( it turns the plate, and there is a vacuum from the pipe) , the weights move freely, the shaft bearings are ok (try wiggling the rotor arm from side to side), there are no tracking marks on the rotor arm/inside of cap. Try pulling the leads out of the cap and checking for corrosion inside.
Is the wiring ok on the ignition system, check there aren't any of the awful crimping blocks or badly crimped connectors.
What colour are the plugs? If they are very different, is there a pattern e.g. the two middle ones on one bank and the two outers on the other?
All fairly basic stuff, but you never know.
Have you checked the vacuum unit on the dizzy ( it turns the plate, and there is a vacuum from the pipe) , the weights move freely, the shaft bearings are ok (try wiggling the rotor arm from side to side), there are no tracking marks on the rotor arm/inside of cap. Try pulling the leads out of the cap and checking for corrosion inside.
Is the wiring ok on the ignition system, check there aren't any of the awful crimping blocks or badly crimped connectors.
What colour are the plugs? If they are very different, is there a pattern e.g. the two middle ones on one bank and the two outers on the other?
All fairly basic stuff, but you never know.