45 Heads

[Flathead fathead]

I have 3 aluminum heads for a 45" HD, one front (a #5), and two rears. The rears aren't marked, are very different compression and aren't the same as the front, one is higher than the #5 the other is apparently lower. I thought they only made #5s and #6s in aluminum apparently I'm wrong. What do I have? I figured I'd have a set milled at least enough to insure a good gasket surface and maybe milled to #6 specs but I'd like to know what I have before I start milling anything.

[duffeycycles]

many were unmarked & many have been altered

[Rubone]

On the lower surface in one corner there may be cast in ribs. The number of ribs relate to compression. The 5 and 6 did not appear until military production started in earnest, the early heads are marked differently. Post pictures of the underside.

[Flathead fathead]

Thanks for your help. One head, the one that seems to be the highest compression ratio, does have three ribs. That's also the one in the worst shape, it looks like something hard bounced around in the cylinder for a while. I'm a computer dumbass and I don't have a smart phone so when the wife has time I'll get her to post some pictures. I've also got a couple old hats that I'd like to trade for parts that I'm going to get her to post also. (I've got a wife that's smarter than me so I don't need a phone that thinks it's smarter than I am too)