[rotorwrench]

The 41A block was a replacement block for the 221 cid engines starting in late 1944. Production was side by side with the 59 series blocks but they aren't completely the same. The 41A has characteristics of the ealier 221 and the later 239. It may not have very thick cylinder walls but it can be bored to 239 specs without problems unless it has core shift or corrosion.