Rolls-Royce Phantom III - head core plugs


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R-R PIII - head core plug tool


If you do not already own any core plug extractors then you will need to make 5 of them.  On the left is the largest one and above it is shown located in an exhaust port plug.  3 blank tools were made with the aim of having them double-ended.


R-R PIII - tool in plug

Attempts to remove one of the smaller plugs ended when the high tensile steel pins sheared off.  The large plug, shown here, managed about 1/4 turn and it was decided that the risk of wrecking the head exceeded the desire to inspect the waterways - so it was tightened  up again.  Inspection with a torch and lengths of wire will confirm whether inspection really need to go further - plus the end plates are easier to remove.    Remember that the plugs are steel and are screwed into cast aluminium where they have sat, surrounded in water, for the last 7 decades!

The following table gives the dimensions and quantities of core plugs in each head.  It should be notes that there are two further plug holes: one is used for the temperature sensor and the other is situated in the water jacket.  All plugs have 4 socket holes.


Cylinder head core plug table All dimensions are given in inches
Outside diameter Pitch centre diameter Socket hole diameter Quantity
27/32 5/16 1/8 1
31/32 7/16 1/8 10
35/32 7/16 7/64 9
35/32 15/32 5/32 2
43/32 23/32 1/4 3