I think I am having problems with my temp guage or sending unit. I was waiting in line to get into a show for quite a long time yesterday, my guage only read 210, With the heat yesterday, I am sure it might be low. How can a check if its the guage or sending unit?

Thanks

 

I don't know how expensive that are but there is a thermal device of some sort that will read the external temperature of hoses.  I've heard folks mention these in other posts for diagnosing gauge or sending unit issues.

Infra-red, non-contact thermometers are available fairly reasonably priced. I just replaced the one that got STOLEN from me just a few weeks ago. It was a cheaper model, but it was around $50, if I remember correctly. Just point and click, and it will give you an accurate temp reading.
Another way to check the validity of your gauge would be to install a temporary mechanical gauge. Most intakes have a spot for one, or you can put one in the pass side head, if there is a threaded hole there that is not being used.

210> on a b-block normally will have it puking before long...

Joel,

Point it at the water neck on the manifold.  That will get you the most accurate coolant temp reading if you have rubber radiator hoses.  If you have stainless steel water hoses you can point it at top one near the engine. 

Yeah, the thermostat housing will give you the best, most accurate reading. You can compare that reading with a reading directly off of the heads, and it should be fairly close, with the head temp being slightly higher. The thermostat housing will give you approximately what the temp gauge should be reading.

You can also check the inlet and outlet sides of the radiator to see how efficient it is cooling.