This is my 59 motor. Gm eliminated the steel line with a drilled galley from the main to the rockers.
848 head entered service for the 56 model year. I have one that was cast in October of 55 for 56 production year. I also have a 5913 head with an early 56 casting date so it appears both were used in 56. I have heard different people state that the 58-63 head is slightly higher compression (factory literature shows higher compression ratio). One of these days I will cc a 57 head and a 59 head and see if there is a combustion chamber difference between the early and late 848 head.
