Breathing new life into the 318 in the Scamp!
Is it a deep thump thump thump?
What is the oil pressure?
I know you used a micrometer on the crank and plastigauge, and had the rods reconditoned, but did you check the conecintricity (sp?) on the big end of the rods with the caps torqued on the bench?
Did you use the factory rod bolts?