RE: mccoy engine
Several have mentioned burning down McCoy stunt engines...
Sure, you can do that. For those of us who have known and loved Fox and ENYA engines, there is an alternative. It is called "break-in."
The ENYA engines, given a half decent break-in, will last until you are so tired of seeing them that they tend to go on the wall and stay there.
Fox Stunt 35s, given a decent break-in, and a steady diet of 28-29% all-castor fuel, will live forever, too. McCoy engines, of various eras, had the potential to give such service. Aside from factory QC, the low prices kept them from being considered suitable candidates for a break-in that cost more in fuel than the engines did, themselves, new-in-box.
The porous, sintered iron pistons are ideal candidates for varnish-equals-fit durability. Two things only - a frying hot run kills them, and a low-oil - or detergent oil - fuel does them much evil. It flushes off the varnish build-up that makes the pistons seal in the sleeve... They still preferred a juicy stack-prime to start reliably... Harder to do today, even with chip/tongue mufflers.
The McCoy Series 21 boat anchors were heavy for their displacement, particularly the .19, but the Dykes ring - if never fried - made a big difference. J.Bowman has rings for most of our engines, and if you have a Series 21 with a Pringles Dykes ring, he may be able to restore a very useful engine for you. Fried Dykes rings never seal for hand flipping... Reasonably used Dykes rings are very durable.
When I was a kid, the McCoys were steel sleeve red heads. Their worst trait was blowing glow plugs out of the head in mid-flight. No way to fake out of that condition... Of course, as a kid, I was more into the burn-it-down mindset than building an engine I could use reliably for quite a while.
We all learn...