The resulting all-alloy M28 engine has multiple unusual features. Its bore spacing is 122 mm, and uses thick aluminium cylinder barrels, hence the lower displacement. The engine was designed for air flow first, thus the spark plugs are located at the top of the head. The four-bolt bearings are sizeable and are fed oil via grooves in the bottom surface of the block. The oil and water pumps are driven by the timing belt, and the design of the engine allows for sufficient air flow with a low bonnet.