Well here's some insight into my idea of fun and hopefully a couple choices for a free plug wrench for ya L.D.
This might be more info than necessary, but since the NGK 18mm issue came into play, here ya go. These pics are fuzzy but I just want you to know that I did have the plug and the sockets here to measure them.
Anyone concerned for my safety or mental health, don't worry, Im drinking.
NGK-R DR8ES-L Spark Plug measures 17.80mm consistently on the flat sides. 20.28mm at the largest, point to point diagonally.
Attachment 187557.
Attachment 187558
I measured this stuff with a Chinese Digital "Very Near" Caliper. I wore my best clothes too.
Attachment 187559
These sockets all come from the same kit.
19mm socket measures 19.32mm consistently at the top of the arcs of the convex inside surfaces, or the smallest inside to inside measurement possible on a six side socket. All socket measurements from here should reference. The 19mm is small enough to work, but close to too big.
Attachment 187567
18mm socket measures 18.34mm
Attachment 187560
11/16 socket measures 17.74mm
Attachment 187561
OPTIONS. I think I have two good ones for ya. I'm 100% positive that I'm not sure where I got em.
The first one, I think its from an 85 200s tool kit. One end says 17, one end says P(plug).
The 17 side measures 17.54mm. The P side measures 18.76mm. Its the longer of the two options at 104.27mm.
Attachment 187565
The second option is a mystery, it measures 18.50mm, which makes it more snug on the NGK. It is however shorter at 72.57mm
Attachment 187566
Let me know which one you want, if either, and I'll send it to you free of charge
