318 with random parts.

66fs said

From the numbers off my 2658920 heads in the 66 Formula S. The chambers measured 63.5 cc up to one at 64.8 cc, with most being 63.5 cc. These numbers are from virgin 50K mile, 920 castings, OEM valves and the lightest valve job to just seal the valves. It took .040 to bring them down to min spec. of 57.3 cc per chamber.

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They must have been milling them different over the years. I've never seen any factory production sb mopar LA head less than 64cc. Most shops only pull about .002-.005 per clean up that's barely .45-.85cc about but less than 1cc ,valve seat is about .005-.015 deep, valve face .008-.010, hard seats raise the 45/exh valve countering that. In other words it doesn't cover 4ccs.