Radiator question

Honored Posters, With Respects,
A couple of Hard earned experiences to lend,

1)On block castings...
Blocks are an cast from 'composite' molds --- an internal & external--- then 'joined',
the 'freeze plug' holes are actually supports for the casting molds.
'Clean' water jackets do not equal smooth jackets, (read core shift & INTERNAL casting flash).
Any Internal restriction to coolant flow (see above) creates steam pockets.
In a constant coolant flow system (automotive) the net result is coolant temps
which vary ALMOST with ambient temps. Restrictions= state of change in the cooling medium.
2)On Infrared Handheld Pyrometers...
An excellent tool, the MOST singular drawback however is the surface of the material
being 'scanned' ... Irregularities, color changes, surface angles, holding angle point to point on multiple reads... I have seen as much as 40 deg F change between readings...

Thx for the Grace Honored Posters :D

williaml,
Apologies for the hijack,
--- don't overthink--- observe & report!