604 inch BBC. World block, lunati crank, grp rod, diamond, Sonny's/brodix conventional head w 395 max effort runner, shaft rocker, bullet, crower, all good parts as expected from a Sonny's build. It's freshly rebuilt which is why it's now 604ci. Also had diamond make set of nitrous pistons w .250 pin wrapped in total seal AP ring and a rebalance of rotator. Have receipts for recent rebuild along w receipts from Sonny's w Dyno sheets. Motor has always been maintained well including leak downs and comp tests.