I have a 74 Challenger with a 440/6, the engine runs great and now with summer here I can see a definite difference in the engine temp, the engine is running warmer at all times and when I stop the radiator "pukes" water/coolant out via the over flow tube. The engine temp is normal when going down the road but when I hit several stop lights or traffic watch out as I see the temp gauge going up quickly. I have a new radiator installed and the engine is new, recently overhauled. Is this a thermostat issue? A water/coolant level issue where the water level is stabilizing? Is there anything else I can do to keep the engine temp down? This is the first time I'm experiencing this.
Thanks!

Do you have a shroud on the radiator? Rising temps at slow speeds is normally an air flow problem. How high do the temps get?

Gotta agree with Stumpy. Had the same issue with my 64 300 after I rebuilt it. Played with thermostats, fans, oversized radiator but it wasn't until I put a shroud on that the problem went away. I suspect a well fitting electric fan, a good on at that if you go that route, would do the same.

3 or 4 core, clean coolant, a good cap, a 180 or 195* thermostat, a shroud, a good water pump and fan set up and no issues with any of my cars. I have foudn that if I fill my radiators all the way up they will tend to poke out some coolant after shut off until they seek their own level, after that no more poking.

The coolant may puke until it finds its correct level. As long as the core is well covered after running (and puking) it should be OK. No need to add more coolant.

Running cool on a roll suggests the radiator is OK. As mentioned, hot at a stop often suggests air flow problem.

How hot does it get at a standstill? Personally, I think 210 F is fine, 220 a bit hot and 230 of concern... even though the coolant should not boil out until 250+.

What fan/fan clutch/shroud are you running?

X2

more info needed

Another thing to consider...new engine you said, make sure it is tuned correctly as far as timing and not running lean, etc.

Aside from that, all the other things as mentioned with a shroud, etc.

Great comments and insight.
The radiator is a 4 core radiator (new), clean coolant, 195 stat, the engine runs great, to me not rich or lean that I can tell. I have a normal fan and fan clutch set up and it works as advertised. I do have a fan shroud but it is more of a custom built one, when looked at closer there is a good amount of room between the tip of fan blades and shroud, also the shroud is not that deep, as it covers about 1/3 of the fan blades as you look straight down. More than happy to ditch that shroud if anyone can recommend a quality fan shroud that would fit the radiator/cowling and cover the fan assembly.

Does it cool on the highway?

As said it saure sounds like an air flow prob. I would get a decent (wider) schroud and a fan with larger dia blades (& how many blades does the current one have?) and the fan positioned (front/rear) the proper distance into the schroud. Not likely it (but might be contributing if way out of line) but curious what is your idle in gear initial cuz that is what the eng is seeing at the stoplight and what is the timing at the RPM it is seeing going from one stoplight to another and what is the WP pulley ratio

are you running a 26 or 22" rad? What water pump - 6 blade AC or 8 blade HP? Headers or manifolds - what part #'s of the manifolds - If a 26 rad, get a 2998326 shroud from summit $80, but get a factory shroud - solid or clutch fan? - 070 or 112 or the MP ? Stat should be good because once it opens - that's it - what fan - 5 blade MP or 8 blade? I ran the MP 5 blade viscous fan/clutch w/180 stat, stock 326 shroud, radiator was recored to a 4 from a 3 - but I didn't really notice a change in temp...I was running 2" Hooker Super Comp headers btw...temp was always 180-210 tops - if at a long light - my timing was 36 degrees total, full advance was all in at 1800...but that was with a 10" 3500 stall converter / 2" hooker super comp headers / fairly large cam /

I'll just add to shakerjoe's post the details matter a lot... including crank and water pump pulley diameters which affect fan speed.

A 4 core radiator can provide lots of cooling... and also needs a lot of fan to pull air through the thick core. If you can post more info and maybe a pic of radiator/fan/shroud it would help with suggestions.

The 4 core radiator is part of the problem. Cooling is about flow. Four .500 tubes is a restriction in the system.

I don't think Chrysler ever used a 4 core radiator. Make sure the water pump is turning crank speed or even a bit faster.

Stop!

Before you do anything you need to find the problem. Throwing parts at it will likely empty your wallet and not fix the problem.



I guess it's time to pull this thread out again.

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/1463521/1.html

It should help you find the culprit quickly. We can go from there after it is found.

Im at this point with this 65 300 vert I just scored on. It's a SF car so no AC. Not sure when the system was flushed last. I have all the maintenance records on the car but nothing on when or if the rad was replaced or for that matter the water pump. I have a new 5 blade with a clutch and have the stock steel fan shroud in route. Its starting to creep up in the 100s here so a temp gauge is probably in the cars future.