OldCarKook,
When these old engines were shipped from the factory in the '40's and '50's, their crankcases were full of unsophisticated non-detergent oil. Although I haven't done the required research, I will bet this oil contained no zinc. If you are running a hopped up 302 with full race cam and double valve springs, this zinc thing becomes a very important issue.
When someone tells 'Joe Stovebolt' the lumpstick in his 216 is going to go flat unless he grabs some Shell Rotella motor oil, they are doing him a dis-service by spreading misleading information.
Stuart
