Just learned this tip at Calif Inliners picnic, from 261 Guru Mike Smith. Flip the head over so you're looking at the surface, look at front left corner, will be below the front stud where exhaust manifold bolts on, but at the deck surface. There is a very small slightly slanted number pad, maybe 1/4" x 1/8" for a 'cast' code, my 53 powerglide head on the work bench has the code 'A21'. What does the number mean, who cares, just use this as a clue for estimating how much has been milled off. If the little numbers are virgin perfect, the head has not been milled. Compare this area on an
milled head to a untouched head to estimate how much has been removed. Please post what you find. Mike says he found this area on 235 and 261 heads. Happy hunting.
