[blownb310]

Originally Posted by Shadowjack

He and many others of us know that 9s, 8s, 6s, 3s, and 0s are hard to tell apart, and that a '67 400 block has the casting number 9786133. No others come close. The oil passage plug is drilled through the number, which is why they were moved to the right cylinder bank.
Year One catalogs used to have this info.

Thanks Shadowjack,

Now I understand.

Does anyone know why the valve relief "eyebrows" are located lower in the bore centerline for the '66 and earlier heads?