The cylinder head is of aluminium and silicon alloy.The two valves per cylinder, parallel and vertical, are fitted in the valve guides and are operated by a single overhead camshaft with cams acting on mechanical type tappets.The valve guides are an interference fit in the cylinder head seats and the internal diameter is corrected, after fitting, using a special reamer.Compared with heads with precombustion chambers, the entire combustion process takes place in the combustion chamber in the piston crown.The cylinder head gasket is of the multilayer metal type, and there is no need to retighten the cylinder head at all during the life of the engine.The plastic cam cover also acts as an engine oil vapour separator.
