We recently purchased a '51 F-6 with 254 M series engine. It was stuck, so we pulled the head and freed it up. Upon inspection I found a small hairline crack running from inside the #3 intake port, extending across the deck and down the #3 cylinder about an inch. Just for laughs, we put it back together and got it running, drove it around a bit to see how everything else worked, and then pulled the engine for rebuild.
After disassembly and a 3 day bath in the hot tank, we looked things over and came up with a game plan for the crack which will include pinning and a liner for #3 cyl. Unfortunately, with the other machine work needed, we're looking at some serious $$$.
Here's the question: We found a 7HA 226 NOS bare block at a reasonable price. Could we bore the 7HA block to 3.500" and use all the parts from the 254 M? What are the differences in the blocks besides bore size?
I had a 50 f6 that used the 254 ci, the engine went bad and we put in the 48 226 "H" block. We used the original intake system as of the vacuum set up. It was hardly any different in power as the 226 runs very nice.