Cylinderheads for trucks

History

Until about 1940, so-called 'flathead' or 'sidevalve' engines were mainly present in motorized vehicles. Certainly in America flat-head engines have been used for a long time. Until about the second world war. Then the so-called OHV (Overhead Valves) system prevailed. A flathead engine actually means that the cylinder head only serves as a seal. The valves for intake and exhaust air are then located on the side of the cylinders, in the engine block. Today, only small 1 or 2 cylinder engines for lawn mowers still use this system.
The disadvantages of a flathead engine are enormous compared to the only advantage: simplicity. The biggest disadvantages are the poor air flow, poor ignition and low compression. The emission is high due to the poor ignition.
In many older engines with an OHV system, an underlying camshaft is used. The camshaft then operates the valves with push rods and tumblers. Truck engines also often use this system.

Modern cylinderheads

Nowadays, a cylinder head is a complicated piece of technology where many air flows and movements take place. The underlying camshaft has made way for the overhead camshaft, also called OHC (Overhead camshaft).