Can anyone tell me the largest practical bore for a 360?, my machinist tells me that .060 over is ok. I recently installed a bored .060 over engine in my 83 RC and a cylinder wall cracked while I was idling in my driveway. Any ideas what might have caused this? I was just sitting there and it went bang, tap tap tap tap........ I took the heads off and the piston in that cylinder was cracked along the top edge. When I checked the bore with my finger I found the crack about 3 inches long along the length of the cylinder. I found another block but it is already .030 over should I have it bored or keep looking for a block?