tryed to start he car up earlier and it wouldnt start,i checked for a spark and there was petrol in the fuel rail and the starter motor was cranking but it wouldnt start.eventually it started and the engine was making a really loud noise that was metallic and in the head. what could this be as it was running ok when i left it last night and this afternoon it was like this.
Marks on the pistons are not a problem. (as long as they're not cracked etc) Marks on the bores are. Turn the bottom end over and inspect the cylinders. Any chips/deep scratches etc are bad news. If you're lucky and they're alright, check out the head. Remove all the valves, check they're not bent or damaged. Also check the valve guides VERY carefully. They must not be cracked or have bits missing. Check the valve seats and combustion chamber for damage.
Now check the camshafts. The lobes can chip with un-intentional impact.
If all is ok, re-assemble and time it up. Turn it over by hand, checking everything is as it should be.
If it's all ok - fire it up.
Oh, and make sure the new belt is correctly tensioned!!!!!