[zellerj]

Get a IR temp gun and shoot it around the block. Where is it hottest? The temp sender does not give you the whole story, so take temp readings of the head etc.

Could be that crude is wrapped around the cylinder walls from past sins. I could not control my temperature for 15 years, always ran about 210 F. I finally bit the bullet and took off the side plate, and found a lot of organic growth crusted around the cylinders. Cleaned that out with a pick and re-installed side plate - temp is now 140 F.

Since you did not have a thermostat, the path of least resistance from the coolant was to bypass the cylinders. If the cylinder walls are all insulated by crude, then the coolant will not do its job. You will see higher temps when this is the case.