DEEZIL!

Soon after the Deezils were built, model aircraft engine manufacturers settled in on nitromethane-fueled engines that employed a glow plug. The glow plug is heated by a battery for starting, but once the engine is warmed up, the glow plug retains enough heat to ignite the compressed air/fuel mixture. In many ways these engines work like the old hot tube/hot bulb semidiesels of the past. There are still model aircraft diesels out there today but they are very intricate, complex and expensive.

In recent years, collectors have revisited the Deezil and there are hilarious Youtube videos of people trying to get vintage NOS Deezils to run. More serious individuals like Adrian Duncan have reengineered the Deezil, replacing the most failure-prone parts with dimensionally correct ones made from better materials. The results have yielded a good running compression-ignition model aircraft engine.

The ’47-55 Deezil remains one of the most talked-about model aircraft engines of all time, but that talk is generally laced with profanity. It’s become the model aircraft equivalent of the Yugo, with a level of infamy that rises to legendary status. Like the Yugo, it’s a poster child for ruining a basically good design with poor manufacturing quality.

 The Deezil featured a die-cast crankcase, bronze connecting rod, composite cylinder and head (two-piece steel sleeve and aluminum head) and a ringless steel piston. The first crankshaft design was a nicely machined oncepiece steel part supported by a bronze bushing. It was later downgraded to a brazed three-piece unit supported by a cheap brass bearing. Piston fit was vital for adequate compression, but during most of the Deezil’s production run little care was taken to clearance-fit pistons to bores. Many, if not most, would not start from Day One due to low compression.