A while back there was a discussion about these cams. It was stated that there were high lift cams in a 2 valve head, and low lift cams in 4 valve heads. So I want to update to a 4 valve head with big valves! I just tore out the cam from a 3-53 motor with a 4 valve head. Have the cam from a 2 valve 2-53 motor, laying beside it. Both of these engines have the latest detroit picture cast on the side of the block. I measure both cams with a caliper at 1.82 on the exhaust. and 1.80 on the fuel lobe. I can tell no difference. Granted I can't see or measure the duration. What am I not seeing. The cam grinder from Washington, said he didn't know of any difference, but if I would send him both he would grind the 2 cyl to the 3 cyl specs. Thanks for any replies Vic