72 Duster with 340 runs too hot

I have recently joined and need some help.I have a 72 Duster with a 340 in it.
I recently had a 4 core radiator made up for me so I can get it to run cooler.
I am using a 22 inch radiator.
It is still getting to just over 200 degrees when stopped at a light.
I believe I have a 180 degree thermostat in it.The fan is very close to it and it is a 5 blade fan. Is there someone out there who can tell me what else I can do?
Use a different thermostat? I'm in California which can be bit hot on some days.
Thanks.  

Has the engine been bored--maybe making the cylinder walls too thin?

What's the timing at?

What's the air/fuel ratio at idle?

Even though the fan is "close" to the radiator, without a shroud, it can pull air from around the radiator instead of through it.  
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Some people are like Slinkys; they're not very useful, but fun to watch when pushed down the stairs.

200 isn't all that bad really. As long as that's as hot as it gets and it doesn't stay there once you get moving. Maybe you'll have to do what I did and install a "pusher" electric fan on the front side of the radiator.  

do u have a clutch fan that is bad and slipping at a light? it is possible your thermostat is sluggish and high. try no therm. for testing cuz it is free. 205 is not too hot and I know of .060" over 340 street cars that run fine. what spark plug and what comp. ratio ? what is the fan diameter ? 17" or larger. maybe u are lean on fuel at idle  

Thanks for the reply. The engine is about 20 over so I believe walls are okay.
I'm actually going to pull the carb off this weekend and check it out or rebuild it.
I also have another one that I pulled off one of my Cudas. I might just try it.
I had a shroud on it before the thicker core rebuild. I don't think I can get it back on with the overall changes made to the radiator, but I will try this weekend.
Thanks again for your input.  

Thanks for replying.I just prefer it to run cooler, not more than 180-190 max.
I am going to yank my carb this weekend, possibly rebuild it or use another good one off one of my Cudas. Thermostat is new, but I may try one which opens on a
lower cooler temp.
Thanks again for your input.  

Thanks for replying Marco.I have a clutch fan on there which is new.The blade is actually a 6 blade not 5 as I previously posted. I have anew 180 thermostat in there
but I am going to go with another one which will open lower and see how that goes.
I am yanking carb this weekend and will either rebuild it or try one out of one of my Cudas just to see how it runs.
Hey, thanks again for your input.  

a thermostat is to help a faster warmup in cold weather, 6 blade is better than 5, I do not see a fan shroud vs. no shroud a big deal, experiment with it I have. spark plugs ? a 1972-1973 340 with 8.5 : 1 comp. uses champion n12y plugs.  

I just put a Holley 750 carb on it and fitted a 160 degree thermostat. It ran fairly cool for a while and then went back up over 200 towards the 210 mark.
I will now see if I can fit a shroud and also check the plugs.
In your opinion, do you think it's better to stay with a 180 degree stat or
should I leave the 160 stat in ???
Thanks for your advice.  

The shroud is super important! Without it the fan is just blowing air around, instead of forcing the fan to pull the air thru the radiator. If a radiator is way bigger than really needed for an engine, you might get away with no shroud, or even no fan at all. But IMHO you need one. Try that 1st. As to the thermostat, putting in a cooler one will not necessarily make the engine run cooler. Once a thermostat is fully open, they are all the same... the coolant is allowed to go thru at full speed. If the engine is going to run 210 it'll run 210 with either thermostat in it.  

That's pretty much what I figured. All it does is that it won't do it's initial opening for water to start flowing until the temperature reaches the 160 degrees or whatever t/stat is in there.
I am going to see if I can get a shroud in there. That was my next move. Thanks for your help.  

just blowing air around without a shroud? I run a 22" wide stock duster 2 core 340 radiator with a 18" fan that is close to the radiator and with or without a shround did not make a big diff. it is sucking thru. and runs around 180-190 with a stock water pump, cheap fiberglass fan, 440 magnum avs carb, block bored +.030" .  

"just blowing air around without a shroud?"

Yes, basically. Your radiator is most likely bigger than you really need, and that's why you are not having problems. But to maximize the efficiency of any radiator, the air needs to be drawn thru all the radiator's fins, not just the ones directly in front of the fan. Read this by Griffin Radiators: Griffin Radiators