This .074 cubic inch engine was distributed by Polk’s Model Craft Hobbies, Jersey City, NJ. This is one of two different sized engines built by Gilbert and sold in kit form. The other size was a .11 cubic inch version. Gilbert, of American Flyer® trains, Erector® Set and Chemistry Set fame apparently tried their hand at nearly every aspect of popular youth hobbies in the 1950s and 1960s, and flying was no exception. The instructions show an exploded view and cover the assembly and running of the engine. The glow plug engine turned a 4″ (diameter) by 3″ (pitch) prop, while the .11 version turned a 7″ x 4″ prop. The conclusion of the instructions noted, “With each successive run the engine should sound much smoother, and a smooth hum will replace the sharp bark which you heard on the first starting.”
View pages 1 and 4 of the instructions. View pages 2 and 3 of the instructions.