Idle temp higher than running temp...normal?

[73Challengr]

I've got a 73 Rallye 340 with a mild to strong build. Rebuilt about 1000 miles ago. This is my first month with the car. It's been a long time since i've driven a classic so trying to refresh my memory.

Engine temp when going down the road is solid at 180. Get to a stop light temp goes up to 200ish, temp does stop climbing, always under 210. Temp comes back down to 180 quickly after starting to move again. Mechanical fan is engaged at idle and looks like it's doing it's job, stock 73 radiator, waterpump, fresh/full coolent.

Is this pretty normal?

[Scooter]

A fresh rebuild will run a bit warmer until broken in. At 1k miles you should be past that. 210F is not horrible if it gets no warmer. Might wan to make sure the thermostat is not stuck open just to be safe. While cold.. pop the rad cap and see if the water is crossflowing. The water should not be moving much when starting from cold. Is it a new radiator? 

[JS29]

 

[73Challengr]

Didn't think of the T-stat being locked open. Will check this evening. Appreciate it!

[Skid Row]

  Original radiator? Have you had a rate-of-flow test done on it?
No less than 28 Gpm.

[73Challengr]

It is the original radiator...the coolant is clean but I get what you're saying. Flow could be low/blocked after all these years. I'm going to check out the possible stuck open T-stat tonight. My Challenger is a driver/not 100% original so if thats not it, I might just get an upgraded radiator to replace it.

[Katfish]

How would a open thermostat make it run hotter?

[7212Mopar]

Lean mixture at idle speed? Engine speed low equal low mechanical fan speed moving less air and engine is hotter. Old radiator also not helping.

[Scooter]

How would a open thermostat make it run hotter?

A properly operating thermostat regulates the speed of the coolant flow through the radiator. If the thermostat is wide open all the time, the coolant will not stay in radiator long enough to stay cool. Worth a check. If it's working normally and the clutch fan is also in working order I'd bet the original radiator is the culprit.

[70 Challenger Lover]

I used to have that exact problem on my Corvette. Once I started using the vacuum advance again, problem went away. That thing will idle all day in 100 degree weather and stay at 180. My Barracuda is The same. I know some don't believe in this but I can see it with my own eyes. If I disconnect the vacuum line and plug it, both cars slowly get hotter while idling. Plug them back in and the temp falls again.

[Bullitt-]

I would be more suspect of the fan's thermal clutch not engaging. Fan will still spin but not at full speed.   
Also do you have a fan shroud?  Overheating while sitting & not while moving is symptomatic of lack of air flow through the radiator from what I understand