I was playing with the hot rod again today trying to figure out the coolant flow issues.
After driving the car for a while I parked it in the driveway and revved the snot out of it to heat soak the engine.
I shut the engine off and took measurements with my IR temp gun.

Old Auto Meter mechanical gauge: 235
Sending unit for mechanical gauge: 222
Top radiator tank on passenger side near hose: 239
Top radiator tank on driver side opposite hose: 233
Bottom passenger side tank opposite hose: 95
Bottom driver side tank near hose: 93
Driver side Edelbrock head measured on center of end: 195
Passenger side Edelbrock head measured close to center on end: 258

My alternator prevented me from measuring the same spot on each head but I got really close.

I've got to have something blocking the water to the passenger side of the engine.

What route does the coolant take through the engine?

It's obvious there's a flow obstruction since I've got a 140 degree temperature drop across the radiator.

The good news is that the monster cooling fan is certainly doing it's job.

Nice ride mine heats up and i will be making a fan shroud for it on monday will let every one know how it cools after that.

Mine just started this issue. The hard part is that I changed the water pump, pump housing, thermostat, cap, fan, and hoses all at the same time.

I have no idea which part(s) is/are the problem. My old water pump housing has a broken bolt boss and I really didn't want to put it back on.

The WP housing would be about the only part that could affect both sides differently (the pump itself maybe). Will it fit back on there long enough to confirm/deny? And check the passages on the current housing when you do

Agree, the WP housing is the best place to start. It directs the cool water to both sides of the engine. If something is fouled up inside it may not be directing correctly.

Me too i have changed all those items too its better but i have never had a mopar street car run hotter than 185 all day for me.!

I do have a problem. The engine heats up. I can't get it to hold a steady temp for very long with all the new stuff.
It creeps up. If I stop and idle it'll drop quickly.
When I pulled in at the gas station it was touching 230 degrees. I paid at the pump and got 7 gallons. When I restarted the engine, the temp dropped 25 degrees.
Everything was off while I was pumping fuel.
The engine heated up again as I hit the road.
Rolling down the road at 35 mph will slowly heat the engine to 230 according to the gauge. idling for a couple minutes will bring it right back down.

If the bottom of the radiator is that cool why is the engine heating up so rapidly? Something has to be killing the flow.

My sb is also "funny" it stays on t-stat around town and slower trafic but on the highway at 60 to 70 mph it seems to slowly creep up. not sure if your elec or reg fan is "windmilling" causing a airflow block across the radiator, i have a 4 core rad and a few things i have read said it may hurt cooling being to thick and slowing the air movement across it, not sure just putting it out there

Cruising along, you should have at least us much air flow (unless the fan is inhibiting air flow, but I doubt it) and more coolant flow than at idle due to increased engine RPMs. Maybe the pump is cavitating? Engine tune? Belt slipping?

almost sounds like your water pump is slipping???

For what its worth my superbee had some issues...turned out the bottom radiator hose was collapsing when reved up

Had somewhat of a similar problem with the 493 race motor. Ran very hot (250 degrees), cylinder head temp was 100 degrees different (hotter on passenger side). Pulled the water pump and blocked the bypass below the thermostat housing. Adapted a garden hose fitting to the temp sender on the waterpump housing, removed the top rad hose and clamped it to block the flow through the radiator. Turned on the hose and noted the water flow from both sides of the waterpump housing. Our passenger side was blocked; very little flow compared to the driver's side. Turned out the block was partially filled and the back two cylinders had residue between them preventing water from exiting the block.

Coolant flow on a big block is isolated on each side; there is no cross-over. With the garden hose attachment, water flows into the top hole of the block (from waterpump housing), up into the front of the head to the back of the head, into the block and foward to exit the lower hole in the block. There is a passage on each side of the front section of the waterpump housing where the water will flow out and it should be the same for both sides.

1) The cooling fan is not blocking air. If it was, there would not be a 140 degree drop in temperature top to bottom.

2) The lower hose is not collapsing. Visual confirmation.

3) The pulley is not slipping. I have a one belt system. If it was slipping I would not be able to charge more than 50 amps with the alternator.

Another annoying problem is the radiator cap. When the engine gets really hot the cap will get loose. I have to turn it 90 degrees to tighten it up again.

I will pick up a new stat and cap from Napa and see if that helps.
I have tested the thermostat. It opens at the correct temperature. Maybe it's weak and can't hold itself open against the flow from the new water pump.
If that doesn't work, I'll pull the pump housing again and verify the passages are good.

I didn't have this problem until I swapped the pump, housing, stat, cap, and hoses all at once.

What water pump housing are you using. There's a thread floating around here somewhere about some housings that don't flow very well.

the problem pump was from 440 source.

https://board.moparts.org/ubbthreads/showflat.php?Cat=0&Number=5957937&Main=5957877

Pulling the stat out completly as a test would confirm or eliminate that problem... plus its easy.

Hot when running, cool at idle usually means a water flow problem. In my experience usually a plugged radiator. But you say it was OK before so unless crud got in the radiator its something else.

If all else fails, can you put your whole old setup back on - housing, pump and stat or no stat as a test?

I'm using the aluminum water pump housing from Magnum HP. I bought it 4 years ago and never installed it. Greg says he hasn't had a problem with any of them but does not know if they came from the same manufacturer as the 440 Source stuff.

The water pump is also aluminum with Japan cast in it. It has the plate behind the blades.

I know it's some sort of water flow issue. It's simply not normal to get a 140 degree temperature drop across a radiator. I need to find out where the problem is.
I didn't mess with it tonight. It was raining. My hand and arm are killing me. Luckily, I have an appointment with the orthopedic doc in the morning.

Maybe I'll mess with it tomorrow if everything is better.

My "Japan" water pump is a Milodon with the little plate behind it and I found it to be no better or no worse than the one I had in it from Autozone. It just has a plate and costs twice as much.

With the temps you provided I assume it is a down flow rad? If so, have you run it with the cap off to see coolant movement when the stat opens. Should be lots of movement accross the opening. Have you taken any primary exhaust pipe temps? How do they compare?