One other thing to consider, the 5913 head uses a smaller port for the water temp sender then the later 848 head so if that is a consideration. As for the 848 head, that head entered service in 56. I have one dated September 55 for the 56 production. The 56-57 motors had a compression ratio of 8:1 where most of the literature that I have seen suggests that the 58 and up motors had a 8.5 CR. Quite a few years ago when Tom Langdon was still working (pre retirement) at GM, he looked up the chamber volumes of the head casting numbers for me which I posted some years back on the inliners site. At the time, the 848 head was spec'd at 79.1 cc. That being said, I have never measured the chambers from a 56-57 head and say a 59 head to see if the bump in reported compression was combustion chamber driven or something else.
Last edited by Dragsix; 07/24/2019 10:49 PM.
