Originally Posted by fast68plymouth
Here’s the “heads with valves” vs the “bare heads”.

With the bare heads the seats are left uncut.
The ID of the seats/diameter of the bowl where the relief cut ends/OD of the as delivered 45* angle that’s made into the seat insert:
In - 1.970/1.770/2.100
Ex - 1.575/1.420/1.700

Very curious to see how both style of chambers look after the new seats are cut... scope Feel free to post "after" pics, too.