Ford V8 Spark Plugs
Hello Richard,
I use 18mm plugs in my vintage motorcycles and I get them quite easily from any NGK stockist at a price similar to common 14mm types i.e. about £3.00 each. I wouldn't have thought the conversion costs were worth it as the money would buy enough plugs to keep your V8(s) running sweetly for a year or twenty!
NGK standard 18mm plugs are A7, which should be more than adequate for most V8s, or the slightly harder (colder) A8 if you have a motor with cylinder heads that glow in the dark!
Another NGK option is the AB7, which is a standard 18mm plug but with 14mm (21mm AF) hexagon. I use these in my pre-war Douglas bikes because space is tight between the pushrods.
A possible problem with inserts is poor heat transfer, so harder plugs may be required. Also, the 14mm plugs in CMP (Mercury) engines are 7/16th inch reach (trust Henry to be awkward!), which are catered for by the Champion H types. I assume the thickness of the heads has something to do with this odd dimension.
If you have any trouble obtaining suitable plugs, let me know and I'll do my best to help.
Regards,
Rhett.
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