Harry A. Miller is known as the owner of the Miller Manfg, Co. or Miller Racing Engines.

-In 1920, he already had a water-cooled, 4-cylinder, in-line engine giving 139 HP at 2,600 rpm and 155 HP at 2,900 rpm.

-The gear made the propeller to rotate at only 1,400 rpm.

-In those same years and based on the Duesenberg car engine, it was converted to aviation.

-It is the 1414 cu. in. water-cooled 12V.

“Miller 4-cylinder, both sides”

-He rebuilt and modified the OX-5.

-In the year 1928, he also made a horizontally-opposed 8-cylinder giving 130 hp at 2,000 rpm.

The Harry A. Miller manufacturing Co. was in Los Angeles, CA.

At the USNA there is a file with number 3462/452.8 about Miller engines between 1927 and 1941.

-Another rear engine has been the XL-510-1 (military A-510-V3) with eight liquid-cooled, in-line cylinders. It was the Double Miller (4-255) L-510.

-They were essentially two coupled 255 cu. in., 4-cylinders of the “Miller Racing Engine” model  of which is mentioned that it gave 720 HP at 5,200 rpm. It was geared.