I am building a 1939 221 flathead and I have the chance to buy some descent iron cylinder heads, but need more information on which iron heads are good and which to avoid. I am looking at a pair of C59A and 81T heads.
I don't believe there are significant differences between the two cylinder heads. C59A should be a bit higher compression than the truck 81T heads, but only a few tenths of a point. 81T motors made either 85 or 90 Hp, depending on the year / displacement. C59A motors made 90 Hp or 100 Hp, depending on the displacement again. Maybe there were other differences, but this is what my feeble memory can come up with today.
I have two good pairs of 221 heads off '39 engines. One was recently milled .060 before tear down. There is a difference in the valve spacing on the 59AB 239 cu. in. series heads. They can be used but the combustion chambers must be machined for valve clearance. On the rear most cylinders, I believe. The Ford parts manual is somewhat vague on which heads are correct for what engine. As a general rule, the "A" letter heads are correct to my knowledge. Letter "A" is cast on top of the heads and easy to see. I have the details on the use of 59AB mods. If you need it, leave me a private message and I'll dig it out. Could take a while as I have lots of books and manuals to look through.
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