That would certainly do it, sounds like someone forgot to tighten the bolt on the distributor when setting the timing. I don't know why the engine would be very hot with a cold rad though unless there is something wrong with the water pump, a slipping fan belt or a blockage or airlock somewhere.Yes, full of water. Think I might have found the backfire problem, I think the distributor had moved round by 45 degrees, I’m assuming that would make it backfire? Strange that it ran well right up to the end of the journey.