Not to drag up something already addressed but the magnums were NOT designed around 200 degrees, the reason they have a 195 T-stat was emissions (and I suspect poor heater performance). They run much better on a 180, especially in the heat. I know I live in ND what do we know about heat, well we have a higher record temp than Texas, it gets really hot here frequently. The 195 just kills power above 90 ambient. Now you can run a intake valley pan to keep the plenum cooler and that helps as well.

 

Yeah the 180 is staying in. Tell me about this intake valley pan plenum cooler.

 

Its not a cooler its just a piece of metal that bolts down over the camshaft utilizing the bolts from the tappet yoke aligning retainer, you know that metal spine that holds down the lifter retainers. Its a splash shield to keep the hot oil off the bottom of the intake so the plenum stays a little cooler. I don't know if there are others than this but here is an example https://utawesomeperformance.com/sto...alley_Pan.html

 

40 to 50 degree intake temp drops? Any truth to those claims? Seems a tad optimistic to me.

 

I haven't tested it but will whenever I have a 5.9 again. I do know my v10 runs 120-140 degree intake temps (or higher at low speed/idle) though where as most of the modern stuff like the LS and hemi that has no coolant or oil exposure to the manifold is about 10-30 above ambient.

 

I think that is fairly standard.... (120-140) I was seeing those numbers on older GM cars/trucks as well. Of course, I think the sensor is reading manifold temp, not necessarily the air temp IN the manifold. Of course, if the manifold is HOT, the air in it is going to be as well. Intake absorbs a fair bit of heat from the rest of the engine, even if it doesn't have coolant running thru it.

 

Keep in mind, a computer is in the circuit here. If you reflash the computer, yes, your engine will run just fine. However, a stock computer and a 180 thermostat has a progressive analog effect. First off, the computer will inject extra fuel to get the engine up to the proper temperature according to its programming. This has other effects. Fuel mileage will be reduced. The catalytic converter will have a reduced life span, sometimes massively reduced, due to burning off all the unburned fuel. Design life of injectors will be reduced due to extra fuel being injected. The end result will be extra cost of operation, In some cases, especially the converter, premature component failure.

I've made a lot of money over the year fixing what other people did because they heard it did this or that. Some things don't really hurt anything, like the washable air filters that flow more air. A waste of money but it doesn't hurt anything. Others, like moth ***** in the fuel tank to really wake an engine up, on older cars back in the day, it sometimes burned holes in pistons. Today, moth ***** have a different formula and will just ruin the catalytic converter.. Major bucks to fix.

 

Cooler air coming in is an old hot rodder trick. I used to put insulation in the gap under BB intakes. Especially the tall blocks. Look at the factory air intakes from the last 30 years or so. Instead of pulling air from under the hood, ducting now goes to the fender or headlight area. I've got a '93 GMC with the duct going to the fender but still has a heat riser tube to stop throttle drop freeze. My old 1954 Dodge with the 241 Hemi had a scoop in the front of the hood to get cooler air in there in how weather. On a couple of cars back when I ran a salvage yard, I'd cut a hole for a scoop facing backward on the passenger side of the hood. This let heat out in town although on the highway, it had a ram effect pushing air down into the engine compartment. The first scoop was on the drivers side like the hood tach Pontiac used. Blowing a coolant hose taught me that was a bad idea.

 

Ran a 180 in a few 5.9s and my v10 (even a supercharged 3.8 gm) with out a tune and had no issues. I think you are giving the computer in these too much credit. Above ~90F coolant temps they go into closed loop operation and have a set target A/F ratio based on the load of the motor. The computer doesn't have a target temperature however. There is this code P0128 Cooling Sys Error / Thermostat Perf which I have yet to see even when my truck never reaches operating temp during the dead of winter. The idea that they "inject more fuel" to warm it up is just patently false because they are designed around optimized A/F ratio for emissions and the engineers recognized they would be operated in climates where operating temp is not obtainable. There was a period this last winter here where my 2010 charger only hit 150 degrees and that was after 9 miles of driving after having it in a heated shop and letting it warm up to 100 before leaving. The shelby durango in my sig has a wide band A/F monitor and the A/F ratio is the same no matter the coolant temp once it hits closed loop around 90 degrees. I will give it to you that a cooler combustion chamber will allow more air and need more fuel in but the reality is your foot will have more of an effect on fuel consumption than that thermostat.

 

My 01 with a 180 have a "Engine to cold" code and my fuel mileage did get worse, I verified that by watching the fuel trims. He would be correct