Onboard temp gauge - where to take reading?
Well the manufacturers instruction call for the first fin. I however use the top of the block, right below the first fin. This is where i get the hottest readings. Based on the mentality that, when using a hand held u should take serval readings and base your judgement on the hottest reading, i fig the top of the head is the best place. you are actually trying to get a reading right around the glow plug, since the glow plug screws into the cyclinber and not into the head, this also supports reading from the top of the block. Plus my temp lead doesnt fit snug against head in between the fins.
One thing is for sure, the temp lead sensor HAS to be 90 degrees from the exhaust port. The intake side of the cyclinder runs coolest and the exhaust side runs hottest. So basically rotating 90 degrees is equivalent to taking the average temp reading.