What is the recommended depth of the spark plug into combustion chamber? Should it be absolutely flush, or as long as the threads aren't showing is it ok?
I read that I am not supposed to stack washers on the spark plug because of heat transfer from the spark to the head. Does this include the washer that comes installed on the spark plug? Or can I add another copper washer on top of that one?
Thanks,
Igino
spark plug depth
Re: spark plug depth
The plug should be flush since the edges of threads could trigger preignition if hot enough. Most spark plug companies list plug depth in their respective numbering system. For NGK, my plug is BP7HS. B=14mm thread, P= projecting insulator, 7= heat range,h= thread reach 1/2", and finally S= standard type electrode.
For a VW engine the thread depth should be 12.7mm or 1/2". You can get an extended electrode which is the P designation above but only the electrode is extended. The extension is for less fouling and better fire propagation. Always use the washer provided by the manufacturer. Hope this helps.
For a VW engine the thread depth should be 12.7mm or 1/2". You can get an extended electrode which is the P designation above but only the electrode is extended. The extension is for less fouling and better fire propagation. Always use the washer provided by the manufacturer. Hope this helps.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
Re: spark plug depth
Thanks Brian! I probably have the wrong depth plugs - i'll check when i'm back at the shop tonight.