See also:

Cylinder head and pistons - decarbonising
1 With the cylinder head removed as described in Section 7, the carbon deposits should be removed from the combustion surfaces using a blunt scraper. Take great care as the head is of light alloy ...

Ford Sierra Service Manual
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Distributor (OHC models) - removal and refitting
Note: During production the engine ignition timing is accurately set using a microwave process, and sealant is applied to the distributor clamp bolt. Removal of the distributor should be avoided e ...