1965 & 1966 396 engine camshaft differences.

One thing to be careful of when purchasing a camshaft for a 1965 or 1966 396 Mark IV engine is to ensure you have the proper oil groove cut in the rear cam journal. The camshaft on the left in the photo is a 1965/1966 unit and the camshaft on the right is 1967 and later. Most aftermarket camshaft makers show 396-427-454 camshafts for 1967 and later for this reason. While all 396 camshafts will physically fit in 1965 & 1966 396 blocks, care must be taken to have this rear journal groove cut for proper oiling. Care must also be taken to determine the year of the block when buying a bare 396 block or partial 396 engine to determine if it's a 1965 or 1966 block. Some cam manufacturers will cut this groove for a nominal charge or a competent engine building shop can have it done. Naturally the associated 1965/1966 camshaft bearing set must be used as well in early blocks.