Gunson COLORTUNE G4074 Manual De Instrucciones página 23

1. Applications
Car and light commercial vehicles (Part No G4074)
A thread size of 14 mm has been used for nearly all cars and light vans produced in the
last 50 years. One exception is the Ford SOHC Pinto engine (1970's) which was 18mm
size (adaptor available) and recently some vehicles have been introduced with smaller
sizes due to space restrictions on smaller 16 valve engines. Note: The hexagon size on
14mm plugs does vary from 1980 onwards. A taper seat plug was introduced with a
16mm (5/8") hexagon (previously 13/16" or 20.6mm) and the 16mm hexagon size has
also been used on flat seat varieties with a revised body shape.
Motorcycles - 4 stroke (Part No G4170 / G4171 / G4172)
A thread size of 14 mm, 12mm or occasionally 10mm, is used. The spark plug
manufacturer's reference code helps with identification. These products has a smaller
internal volume which maintains the normal compression ratio and a higher heat range,
more suited to high performance engines.
Motorcycles - 2 stroke
A thread size of 14 mm is almost universally used as there are no space restrictions
caused by valves.
Garden machinery and power plant engines
A thread size of 14 mm is generally used.
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