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Cylinder head 4 1/4 L turbulated

Part Code
R-R Code
Bentley 4.25L cylinder head

The 'turbulated' description of the cylinder head refers to a detail of the combustion chambers. It was fitted up to the end of KT chassis numbers in series K. For more details refer to this link.

The turbulated cylinder head is not suitable for use with high compression pistons.

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.