After the Plenum/Intake change, I replaced the T-stat w a new GM stat. The engine maintains 201 not the 195 specified on the stat. Is this normal? I am considering a Stant replacement, since I think 195 sb the high, and gives a little more wiggle room to react if the temp starts climbing. Feedback appreciated! Thanks...

The thermostat only controls the minimum operating temperature. Usually, the fans control the running temperature, and they don't come on until the ballpark you mentioned.

Everything sounds good, as long as the temp stays there.

So far nothing over 210. I am not sure why it would have been running cooler previously. Hmmm....

It'* possible that the previous thermostat was a lower temp thermostat, or the thermostat was defective.

The way it should work is the engine warms the coolant to 195*, at which point the thermostat opens, and the only means of temperature control is the thermostat closing again because the coolant is too cold, or heat dissipation to shed heat built up in the system. This is controlled through air flowing through the radiator, which is accomplished by the vehicle moving through the air, or by the computer flipping on the fans (now that I think about it, 212* sounds more correct) to shed some heat.

This puts optimum operating temperature range at 195*- 212*.

The only way to lower the operating range is to put in a cooler thermostat (180* is common), and to have your computer reprogrammed to switch the fans on at a lower temperature as well (190* I think), which would put the new operating range at 180*-190*.

Most believe that the non supercharged engines run better hotter. You are running exactly where you should be. As far as your concern with reaction time? The only time it would make a difference would be if you are overworking the engine, which you can react to in either case, or a failure of sorts, in which case you will not gain much more than a few seconds.

A side note, under normal circumstances, it takes a lot to run a 3800 hot, and usually the transmission would overheat first anyway. I don't know that you would notice a difference anyway, as the PCM always indicates 210* on the gauge when it is in the normal operating range.

In all honesty, drive it and enjoy it, and if the gauge starts climbing for no reason, then you have a problem, and need to track it down.

Thank you for the feedback! I will leave it alone. Guess I am just a little nervous after having done so much to the engine. It all seems fine. I need to take this on a 600 mile journey (300 each way) soon, and want to make sure I have accounted for all possibilities!

Another thing to add, these engines being solid cast iron, can put up with a lot of heat. As long as there is a reason for it, I don't start worrying until about 230*, and you can usually get away with 250* without issue. The gauge indicates critical overheat (idiot lights and alarms) and pegs out at 255*. Only sheer negligence or a catastrophic coolant loss can put the engine at that temp.

I have heard more engines survive 280* than killed by it, but usually something is not happy about it at that point.