Replacement Cylinder Heads

Our new cylinder heads are dimensionally the same as the original cylinder head manufactured by Rolls-Royce. However where Rolls-Royce manufactured cylinder heads for the small horsepower engines in cast iron ours are manufactured in a high tensile grade of aluminium. This is not without precedent; cylinder heads for the late Phantom 1 and all Phantom 2s were cast in aluminium. The aluminium gives improved cooling and a much-reduced casting failure rate.

As supplied our cylinder heads are fitted with valve guides and valve seats suitable for lead free petrol. Core plugs and push-rod tubes through the water jacket are fitted, and the cylinder heads are pressure tested. They are supplied with all new studs in place, and are finish painted in gloss black. A new set of valves is provided with each cylinder head; however these are not fitted.

If required we can supply a complete cylinder head assembled and ready to fit to an engine. The only additional work that will be required is the setting up of the rocker gear. Please enquire if you are interested.

During the course of production of both the Bentley 4 1/4L engine and the Rolls-Royce 25/30 a similar change was made to the cylinder heads on both models. The volume of the water jacket around the spark plugs was increased to improve water circulation and improve the cooling in this area. In the case of the 4 1/4L the later heads are distinguished by having two extra core-plugs part-way up the side face of the cylinder head above the sparkplugs. These are positioned between numbers one and two, and five and six, inlet ports. There are no other major external differences.

In the case of the 25/30 cylinder head the extra volume within the water jacket necessitated fitting longer cylinder head studs along the spark plug side of the cylinder head. This modification was introduced at the start of M2 chassis series. In order to fit our replacement cylinder head to an engine from L2 series a new set of twelve studs GER223 will be required. Unfortunately it is not possible to remove or refit the studs with the cylinder block in position!

MOST IMPORTANT
It is essential when using a car equipped with an aluminium cylinder head that the coolant is made up of a 50% mixture of water and anti-freeze, if a water-based anti-freeze is used. The anti-freeze must be renewed on an annual basis to ensure that its corrosion inhibition properties are maintained at full strength. Failure to do this may lead to premature failure of the cylinder head for which we will not be liable.