The head is off because I had the head off and just put it back on that way - the engine needs to get torn back down and cleaned thoroughly before I plan to run it. The head will go on the right way when I get it back together. The backplate is in fact missing a screw - the boss for the screw is busted off. I put some JB Weld on it to make a new boss and just need to find a screw to fit. This engine does use a head button, and I did happen to find "40" on the top of the engine mount which I didnt notice before.. I just didnt know the manufacturer of the engine. So if this is in fact a Fox 40, a few questions.. Is it worth a snot, or is it a crappy engine? Is it supposed to make decent power? If I use it, It'll be going onto a Airboat. I also have a K&B Sportster .65 NIP that I will probably use first. I plan to run 5% nitro / 22% oil in either of these engines.. hopefully my LHS has some plane fuel with all castor in it. This seems to be the ticket from what I've been hearing.

Thanks to all that responded.. Now that I know what I have, I can do a little more digging. Anyone know about how old this thing is? Looks like it should be 1975-1986 roughly..