IOE engine

A few automobile manufacturers, including Willys, Rolls-Royce and Humber also made IOE engines for both cars and military vehicles.

Rover manufactured inline four and six cylinder engines with a particularly efficient version of the IOE induction system.

[citation needed] Disadvantages include a combustion chamber of more complex shape than that of an overhead valve engine, which affects combustion rates and can create hot spots in the piston head, and inferior valve location, which hinders efficient scavenging.

At TDC, the piston almost touched the angled inlet valve and provided good 'squish' to the combustion chamber itself, offset to the side by half a cylinder diameter.

[8] The resultant combustion chamber shape was a near-ideal hemisphere, although inverted and tilted from the usual "hemi-head" design.

[8] The spark plug was centrally mounted and this,[6] together with the turbulence generated by the squish,[8] provided a short flame path.

[6] The thinness of the gas layer between piston and inlet valve was so confined as to reduce the risk of detonation on poor fuel, one factor that kept it in service with Land Rover for so long.

[citation needed] The IOE layout enabled Rover to use larger valves than would normally be possible in a small bore engine, allowing better breathing and better performance.

The shape of the combustion chamber as an "inverted hemi-head", along with the angled cylinder head joint and pitched-roof piston crowns, had earlier been used in the 1930 Van Ranst-designed Packard V12 engine, although in this case the valves were both in the block as side valves and the spark plug was poorly placed at the extremity of the combustion chamber.

[10] The IOE valvetrain layout was used extensively in early American motorcycles, mainly based on a French design by De Dion-Bouton.

[19] Rolls-Royce used an IOE straight-six engine originally designed immediately prior to WW2 in their post-war Silver Wraith.