please help , no1 piston exited through the sump, so stripped the engine and found piston no1 and no4 to be all carboned up. have fitted new block and rebiult. engine run fine for the first 50 miles approx then started to run like it was on 3 cylinders , removed spark plugs only to find no1 and no4 plugs really black and soaking wet on no2 and no3 plugs. cleaned up plugs and starts and runs like a dream only for it to do it again approx 40 miles later. anyone got any ideas would be much appreciated.