I have tried to "burp" the system 3 times and my water temp guague still goes from 160 to 210 in a flash then bounces back down to 160. The guage will show correctly slowly moving up to 160 while warming up. After the car is warmed up, the needle will begin to bounce to 200-210 or so then settle back to 170-180. I have a hi flow summit aluminum water pump, could that be causing the problem? I've never had this problem begore.

If you have a good gauge, you might be reading the changing temps when the thermostat opens and closes. What temp is your 'stat?

And...where is your temp sensor mounted - intake, head, ? Is it electrical or mechanical?

if it is a bigblock and you have the sender mounted in the head,that could be it.
i put the sender in the head once on a 454 and got some crazy readings. had to relocate it to the intake.

It is a small block with a mechanical, cheapo SunPro, gauge mounted in the intake by the 180 t-stat. I have already replaced the gauge and it is still happening. Also, I have never seen any water come out the overflow hose from the radiator. I read somewhere that using a hi flow pump could cause this problem also. Just don't want to swap if it is not the culprit. I have always used Autometer gauges and never Sunpro, however, I have seen other people use them with no proble. Maybe more "burping" ?