That's strange...I have spark plug sockets (have a rubber thingy to hold the
plug) marked 13/16 and 5/8. I think I bought the 13/16 when I owned a '63
Ken Lyons '97 Brilliant Black/'90 Classic Red
Inside the Beltway
[Remove the first two digits to reply]
There are a lot of metric wrenches that are almost the same as SAE
sizes, for example 13mm and 1/2", 11mm and 3/8", etc.
Both 13/16" and 5/8" correspond closely to metric sizes and since plug
wrenches are hex rather than 12 point, they can be a little loose w/o
damaging the plugs.
XS11E, Killing all posts from Google Groups
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Spark plug socket dimensions don't refer to the distance across the
flats, which could well be 16mm - they refer to the thread size, and the
flats are always the same size for a given thread. No idea why.
It must be a weird British convention then:
Spark plug spanners (and *only* spark plug spanners) are sized by the
thread major diameter here. A bit of Googling suggests the rest of
Europe uses the actual across-flats measurement, so maybe the US does
the same. You learn something new every day!
I can always post a picture of one of my car's NGK BKR6E11-IX plugs
sitting in a "10mm" socket...
The link you posted has spark plug sockets listed by hex size across the
flats, exactly as on this side of the pond.
There are 14mm thread spark plugs with either 16mm or 21mm hex sizes. How do
you handle that?
You seem to be stuck in the old Whitworth system where the wrench size DID
correspond (somewhat) to the thread size.
As this is not a binaries group, you would need to post the picture on such
a group. Please do so if you can.
B : 14 mm thread
KR: 5/8 hex, Resistor type
6 : Heat Range
E: 19 mm thread reach
11 : Wide Gap, 1.1 mm
IX : High Performance Iridium on firing end
This comes from their partnumberkey.pdf file available on NGK's website.
Where did you get the 10 mm number from?
It's definitely a "10mm" spark plug socket with 16mm across flats, as
per the link I posted. Do I really have to pull out a plug and
photograph it in the socket?
The socket I use is engraved "Socket for Spark Plug 10mm". The
continental Europeans would call it a 16mm spark plug socket (more
I think spark plug sizing is just one of those things which gets lost in
transatlantic convention, like "hood", "boot" and "rocker".
Remove the little rubber inside the socket. Fit the socket on the plug by
hand so that you can feel it slide into place. If the plug has corroded in
place, you will need to use a piece of pipe as a handle extender on your
wrench. Make sure you are attempting to turn the plug counterclockwise. The
plug will come out!
Done the above but still no go
My plugs are in a recessed hole abt 6 inches deep
I'm wondering if there is some kind of "crud" down
there say wedged in between top of plug and sides of
hole that is blocking the wrench form seating on the
Just seems like no matter what I do I cant get the
wrench to 'seat" on the hex head of the plug!
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