Every thermocouple has a time constant... some are faster than others. I experimented with EGT probes on a turbo car and found that longevity was inversely proportional to time constant (due to rugged construction) wink But you're right, for the absolute most accurate and repeatable temp measurements that's the way to go. I assumed (there's that word again) that mine is close since the t-stat opening temp (on 2 different 180 stats) is very close to what I see on the gauge...

I just find it hard to believe that a couple of pieces of cardboard baffling are going to make a significant difference to the airflow through the radiator while driving with so much frontal area open shruggy
I don't have an overheating problem at idle either, just wanted to drop 10 degrees while cruising.

If the core is that marginal I need a better one anyway. I do agree that (sometimes) one gets what one pays for smile Glen-Ray is a bit steep for my budget but I'll buy one if I have to!