After over 60 years of flying model airplanes, I have accumulated all kinds of engines and engine parts and when I look at them I keep finding all kinds of oddities and have no idea how I got most of them.
Back in the early 50s a neighbor kid got a used glow conversion side port Gwin Aero 35 that was eventually passed on to me. I ran it and found that it got a 10x6 prop all the way up to a whopping 3,000 rpm. The performance was so bad that I threw the engine away but I kept the glow plug, which happens to be a O&R plug with a 3/8" diameter thread.
I have a Sky Fury 0.049 glow head even through I have never owned a Sky Fury.
There was a Collecto in the Denver area last month so I handed four engines (a first version Wen Mac, a Thermal Hopper with almost no running time, a David Andersen Mark III 15, and a long shaft Fox 59) over to a friend who was attending to see if he could sell them, but there was no interest in any of them. When I got the engines back I was looking at the Fox and found that the needle valve extension was on the right side right behind the exhaiust port. I got this engine from the original owner back in about 1952 and have never run it. Thinking that if anyone ever ran the engine they would not like burning their fingers while trying to adjust the needle, I decicded to turn the spray bar around. This turned out to not be an easy project because the spray bar was made out of round brass bar stock instead of hex stock so there is no way to hold onto the spray bar body except with a pair of pliers. Having 60 year old castor oil on the threads did not make it an easy thing to turn the nut. When I got got the spray bar out I checked the thread on the spray bar with a thread pitch gage and found that the thread is a 10-64 thread! Apparently the entire sray bar including cutting the threads was done on a lathe.