Overheating 360 new engine
1- the belt is going over the top of the water pump so it's being turned the correct direction (assuming you have a standard rotation pump)
2- those fans can only pull air across the part of the radiator they're literally touching, which means your fans are pulling air across less than 50% of your radiator surface area by the looks of it. That's terrible
3- that looks like a March 40430, or the "style track" system. You should confirm that, and see if you can get exact diameters (like the published specs) for your water pump and crank pulley diameters.
4- what water pump is on the car?
If you in fact have a 5" diameter water pump pulley and a 7.5" crank pulley you're driving the water pump at 1.5:1. The most Ma Mopar ever drove one from the factory was 1.4:1, and those cars used the 6 vane standard pumps not the 8 vane HD pumps. .95:1 got the HD pumps, as the pump was overdriven for the AC cars (for a better fan output) the vanes were decreased. It's unlikely that's enough to cause cavitation, but, it was done that way for a reason.
So here is a fun fact. My radiator is a champion brand. They list a radiator with 2 fans and a shroud part # EC2374-2374FS10SP The fans are rated less than 900cfm each. This unit is rated for 375HP. Why such small fans??
Because they're just selling cheap *** fans to make some money. That's not nearly enough CFM to realistically keep a car cool in the real world.
I actually run a 26", 3 row Champion in my Duster. The radiator works great, my electric fans never run if I can maintain a constant 30+ mph on the open road (not in stop in go), regardless if it's 110°F out. But under 2k CFM isn't even close to enough for a fan set up. The factory mechanical fans move in the vicinity of 5k cfm if I remember correctly.
I went through a similar issue. I did not read through all the comments but there were a few concerns that come to mind, and one of them is not air flow. I sealed everything, running a 3000 cfm fan, i can touch the radiator fins and they are not burning at all when my engine was at 205-210. The things I mention can al be done for free also.
First thing is make sure that the March Performance is turning the water pump the same direction as stock as you may be pulling the fluid at the pump rather than pushing it. It will still flow coolant, but not well.
Second, how is your heater core hooked up? Do you have it looped, or straight to the heater core and straight back? Either way, the coolant takes the path of least resistance. Make sure there is an inline shut off valve of some sort. Coolant is coming out of the head (hottest point) and if looped to the water pump, it is just flowing that hottest water back into the water pump to push through the block again. This compounds the heating and gives you a giant hot spot where your temp sensor is.
A way to test this theory is to put a set of vice grips on the hose going out of the block that is supposed to go to the heater core. This will stop that hot water from going back into the water pump and force it through the thermostat and radiator.
Yeah, so fun fact, a heater core is actually a radiator. It just sheds it's heat into the passenger compartment and the returning coolant will be cooler than when it left the head. You shouldn't have to disconnect the heater core to get your cooling system to work properly.
Here is what we did to get a performance 440 with the serpentine Setup to run cool.
Previous setup was box shroud and electric fan, was trapping the heat in the radiator.
Got rid of the electric fan and it's Restrictive shroud and replaced with an 18" solid mount Silent Run fan 3/4" away from the open radiator.
Runs cool now, no problem.
First layout of the test 14" silent run fan we had on the shelf. Then ordered In the new 18 inch solid mount fan, installed it and it took care of the problem.
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Ah, there it is, the least efficient fan in the entire thread. Riveted design is actually dangerous, there's a thread right on this board about one of those vanes parting ways with the engine running.
*MUST READ*--Flex Fan Danger--Be very careful working on old cars
A properly set up electric fan system will beat the brakes off that hunk of junk. I actually took a fan very similar to that OFF of my car when I installed the Ford Contour electric fans I run now. The electrics are better hands down. Once the volume of air coming in through the grille exceeds the output of the fan, spinning the fan is just wasting horsepower. It's bad enough with a clutch system, but at least then you're not spinning the fan at 100% of the engine RPM the entire time.