Being a diamond block never meant much to me.The only one I ever used came out of a Bay City swing shovel,it had plain old valve seats,(no hardened seats) and weighed four pounds less than a standard A block I weighed along side of it.After they were weighed I took even more off,I had to take it out to .125.over to get a straight bore.That machine had an oil bath air filter,and it still got enough grit through to wear it out.That engine had no numbers stamped on the pad and the texture of the pad was the same as the rest of the block,never was ground off.That engine is in a 28 roadster pickup now,B head,B cam,cheapo JC Whitney two tube radiator,and never,ever overheats.