I'm going to start from the beginning. It has a 305 TBI in it with automatic 700r4 trans. I drove the car for 4 months, having to put a new Summit race radiator, powermaster 140 amp alternator, and afew other things along the way. Well, the motor had 166 thousand miles and it started overheating. So I thought it was thermostat. Pulled it. Replaced it. No go. Next step was water pump. Same. So, I did a motor swap thinking the worst. Well, it's "overheating" too. I thought my radiator was clogged, so I took it and exchanged it for a new one. Still having problems.

Long story short, I pulled one motor and put in a totally different motor with all new stuff and am having same problem. No smoke, no bubbling, no coolant loss. The motor doesnt even ping like a hot motor would when you turn it off. Ive been at it for months and im stuck. Any ideas?
Parts replaced: water pump, radiator (twice), thermostat (twice), new hoses, new coolant, bigger fan (blowing correct way), whole motor, intake manifold, headers, dual exhaust, temp sending unit (ones on each side of block), plenty more.

Sorry if this seems like a "same question, different thread" post but all the other posts I saw just didn't go as in depth as my problems go.

And one more thing. It keeps overheating while sitting there at IDLE. Too scared to drive on road yet to see what happens.

gages man or something along those lines just guessing. sounds like your going by the gages get a laser pointed thermometer and see what it says on the block and i would say the rad. kinda like this uint or a better one http://www.autozone.com/autozone/acc...ier=951642_0_0_

I forgot to mention another thing as well. I replaced the radiator because the passenger side (side with the cap, overflow tank, tranny lines, and bottom hose) is getting hot to the touch but the driver side is staying much cooler. I never payed attention to see if it did it before. Is that normal?
I also don't have pressure building up (i.e. Hoses won't get hard but it will pass a pressure test)
I got a new aftermarket Summit temp gauge but the fitting on the end is the wrong thread to screw in to my block. Sum-g2930 is the number I believe. And sum-380455 is the radiator.

Nope. Not normal. Coolant flows out the bottom passenger side of the radiator, into the water pump, through the engine, out the intake and into the top drivers side. When you replaced your water pump did you get one that rotates the correct way? If you have V belts, you need standard rotation. If you have a serpentine belt, you need reverse rotation. It almost sounds like you have the wrong pump and its trying to push coolant backwards through the thermostat.

I'm lost ...

If it's not bubbling, leaking coolant, or acting" like it's overheating - what makes you think it is overheating? The guage reading? Forget the guage - if it's not boiling over, it's not overheating.

Have you tried a new temp sender? Driver side head between #1 & #3 spark plug.

Maybe guage is just off - what is it reading? (anything under 240 is NOT overheating).

Electric fan running?

Air dam under radiator in place and in tact?

I replaced the temp sending unit and the fan control unit on each side of the block. I investigated it today with one of those temperature guns and my gauges are horribly off. I bought a Summit temp gauge but it is the wrong thread to screw in to my block. Any suggestions on a good aftermarket temp gauge?
And thank you very much for the help guys. Very appreciated.

The gauge starts out at 100 and will sit there and then it steadily creeps it's way up after about 10 minutes and buries itself above 260. This is all at idle. I did a motor swap and have not driven it on road yet.