The Perky .191 cuin. (3.13 cc) Class A spark ignition model was an early example of a model engine using an atmospherically-controlled one-way valve to regulate its induction system.  The manufacturers, Baycraft Miniature Motors of 23 Miner Street, A11, Boston, Massachusetts, referred to this as a "clapper valve", although later manufacturers of such engines used terms like "reed valve"  "clack valve" and "diaphragm valve".

In its original sandcast form, the Perky was introduced during the latter part of 1940. The early examples featured one-piece blind-bored steel cylinders with a vertical plug, but later models from 1941 onwards switched to a removable cast alloy head with a striking rear-angled plug, along with die-cast components. All pre-war models featured a unique timer design which was activated by a cam stamped into the rear outer rim of the conical sheet metal prop driver.

During 1941 work was started on the development of a stroked 0.232 cuin. (3.8 cc) Class B version of what was now referred to as the Perky "Supercharger A". However, very few of these were produced before WW2 intervened in December 1941. There was also a single prototype of a 0.610 cuin. (10.0 cc) unit which featured crankshaft front rotary valve (FRV) induction. The production of this model was prevented by America's entry into WW2, never to be resumed.

After the war, only the 0.191 cuin. Perky Class A model was re-introduced, now featuring a more conventional timer activated by a cam on the crankshaft. A different manufacturer, the Victory Machine & Tool Company of 228 Sanford Street, Brooklyn, New York was now involved. Production continued until late 1947, when the advent of the glow-plug rendered spark ignition obselete overnight. A few further examples were produced for collectors in 1962 by another company, using original parts recovered from a Brooklyn warehouse. 

A detailed article about the Perky engines will appear on this website in due course.