Milled your head lately?
By Jim Merritt
There you were, three loooooooooong hours into strolling rows of vendors at Hershey, when all of a sudden the late afternoon sun dances off a valve seat and smacks your conciousness liked a stunned mullet on a boat deck -- it's the 235 head you need!! BUT!! The guy only wants $25 bucks for it ... you wonder if it's worth it or just a pricey boat anchor. The question, therefore, is ...
And if it has, how much?
Look at the under surface of the head, front left (driver's side) corner for a very small and slightly recessed area measuring approx 1/8" by 1/4". This is a "pad" for a casting number. My '53 235 passenger car head has the number A21. Now these are "cast" (slightly raised) rather than stamped in.
What this number means -- I have no clue. However, it appears to be the only simple means of determining if the "SURFACE" has been milled. If this little cast number appears unmolested and very readable, the head may have never been milled. If the numbers appear ground down somewhat, however, milling has taken place. And if they are almost gone, then quite a lot of milling has been done.
I don't believe you can say exactly in thousandths of an inch how much has been milled by eyeballing this number. But you should get a pretty good idea if the head has ever been on the milling machine. While this number can be measured with a micrometer etc. to determine the exact thickness here, doing so only leads to unanswerable questions as to repeatability of factory castings.
So at the next swap meet or core pile, you find a 235 / 261 head, this tip may help you decide "purchase" or "pass" on an otherwise questionable used head. Does this number appear of every 235 or 261 head? Not sure, as I've not seen ALL the heads out there, YET.
(Here's a bigger image of this head, if you need it.)
Bolter # 57
P.S. I must credit Inliner Mike "261" Smith for passing this tip along at our 2002 Lodi,CA meet.
v. January 2006
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