Because I feel bad about hijacking the 2 blade thread

[Cool Hand Lurker]

Cool Hand,
I don't remember the dimensions of the exact spot. I have a center punch mark on Vermins' head, but I can't get out there to measure it.
Best to look inside an OLD head, for the spot. I wouldn't want to catch HELL, for advising WRONG (The Dog just put his ears DOWN, WAY DOWN)
Bill W.

Bill, I did a search and found the post from 2015 where you mentioned the location. Here it is. Thanks again!

#4 cylinder on Datsun 210's would get SO hot, valve seats fell out & usually scored #4 piston.
Temp gauges installed in Model A's should be in the rear of the head, to monitor the HOTTEST SPOT, "might" save an engine! ! Study the rear of a head for the SPOT to drill, in the left side, about 2 1/2" or so, from the rear of the head.
Chief ALWAYS located them there & he knew his ****, & he taught me all his TRICKS, that worked well.
Bill W.

 

[Cool Hand Lurker]

Here is where it goes on a GAZ head.

Thanks Vince, you always come along and play the trump card!