What is a 455 Pontiac engine boreed 60 over?
When an engine is bored over, it means that the cylinders have been enlarged to a larger diameter. The number "60 over" means that the cylinders have been bored out 0.060 of an inch larger than the original size. So, a 455 Pontiac engine bored 60 over would have a cylinder bore of 4.180 inches.