If the head bolts werent tight then this could be the prob. or a factor in it.

ignition timing, why you have a distributor with adjustment on it, can Advance ignition (turn dizzy clockwise) Retard Ignition (turn dizzy anti-clockwise) if your facing the distributor from pass side.

If this is wrong then it will be difficult to start.

All earth straps connected up, gearbox, head-inner wing?