Initially engines were built by the Aircraft Engine Corp. in Oakland. Later, towards 1929, the Comet Engine Corp was founded.

-The Comet 7D, a seven-cylinder, 130 hp radial was followed by the 7E model that gave 165 hp.

-They also made an engine with six inverted cylinders in line that was cooled by both liquid and air. (Mixed cooling)

"Mixed cooled Comet"

-The cylinder, although surrounded by liquid, had fins on its outside for heat radiation. It gave a power of 138 hp at 2,350 rpm.