May I suggest you check out the Fox Website. http://www.foxmanufacturing.com/ Fox has had ABC engines for many years.

Duke Fox was of a personality totally about himself although a good-hearted person. He refused to accept new technology early on in the '70s and could not understand why HS dealers were not selling his engines rather than the imports. I spent several long times trying to get him to accept that the new RC fliers wanted plug-and-Play, not 2 hours of break-in. However he did start making changes but rather late.
Somewhere around the late '70s or abouts, Duke was involved in some harsh charges for which he did some time. I still think he was framed however the model trades people dropped FOX like a hot potato.
Duke passed on and his wife ran the business but later passed on also. Fox just never accepted the hard-core small margin trade of models and engines that came to be in the business. Their engines are so very overpriced that I don't know how they move any. They still live in the 40-20-40 hobby market world which no longer exists. If they supply you with an engine at 1/2 list price that is still 10% of the retail price above the price they sell to distributors which is 40% of the advertised retail price.

Back in my CL stunt days, I flew a number of Fox .29, .35, and .40. After about 4 hours of in air brak-in that .40 was as good as my George Aldrich expensively modified Super Tigre.

Now back on topic: Fox engines are really specialty engines and they are very good engines, but not for the plug-&-play operator. It takes some time to get them going.
I have a retired GB Eaglet 50 with a Fox .25, over 20 yearas old, that must have 150 hours of flying time. I have no doubt that engine would today start right up and fly and fly with no problem although it has not been started for over 2 years. I just need to be sure it has a good slug of castor in the fuel.