It was a vertical, four-cylinder, four-stroke, air-cooled engine designed by A.A. Mikulin. The engine was capable of maximum of 35 horsepower at 1800 rpm and was later improved to 40 horsepower.

How to Get Four-cylinder
Tools + Mikulin

Four-cylinder Doodle Tanks Combo
+Leaf Spring = Infantry Tank Hull
+BT Hull = V-Type