Iridium spark plugs ST1300

Andrew Shadow said:
No, there is no contact.



Given that the difference in the amount of material between a spark plug that is threaded in this area and one that isn't can't be that much as the difference is only the amount of material removed to create the threads over a fairly short length I have to wonder how much of a difference it can make in heat dissipation. Maybe it does.



I never found a good explanation of why this area is sometimes threaded and sometimes it is not. I gave up looking.
Click to expand...
Maybe that extra girth is just for extra material strength? I'm not sure.

I see that the correct term for the ST1300 thread style plugs are called "half threads" and the NGK link below does have them designated as an EH thread reach. EH = two thread reach lengths, 19mm overall length and 12.7mm "half thread reach".

A great site for everything sparkplugs and lots of page links to click on that might not be apparent like on the overview page click in the black box for iridium IX type plugs.

https://ngk.com.au/products/spark-plugs/
 
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