Scott,often its a lack of airflow at idle/slow speed that can cause a motor to heatup in traffic .
But since it heats up so quickly it may have mult issues like poor fan airflow at idle thru the radiator along with an improperly tuned motor which can cause the engine temps to rise faster then normal .
But we need a lot more info like:
Does the motor/radiator actually over heat and what is outside temp when this is happening?
Have you tried a new stat and is yes what temp and is it a hi flow or std flow stat?
Are you running a std or hi flow/volume water pump?
Are you running a 50/50 coolent mix?
Have to verified the temp gauge is reading properly? If motor doesnt ever really over heat then that may be a clue that the tmp gauge is not working properly,you need to verify it.
Is the radiator 3 or 4 core and its age?
Does it have stock fan and if so what type,clutch fan or std non clutch fan? I hope not a electric fan setup as they arent as good for more stock type setups,they do have thier place & are much better suited for high output perf engine combo's with lrg AL radiators IHMO.
If you have a clutch fan,is the clutch new or old,std duty or hd/ac type,thermostatic?
I always fine the ac/hd fan clutches do a better job of cooling a bbc in traffic which is why i run a hd one)
Has anyone verified the fan clutch is working properly?
Do you have a fan shroud,if not you need one.
Are you running any kind of perf cam,if yes what base and total timing are you running?
you need approx 18 deg base + 18 deg mech in dist in by 2800rpm for 36total by 2800rpm.
(Retartded timing/esp base timing can contribute to heating up in traffic)
Are you running a vac adv which you need for a street motor.
(No vac adv or vac adv hooked to ported vacuum with also contribute to heating up in traffic.
Is the vac adv hooked to full intake vacuum all the time when it should be for most setups.
The vac adv could simply be defective/diaphram riped/torn and notadv the timing at idle .
Running low grade fuel in a higher comp motor can also contribute to higher temps.
Lean fuel calibration or a vacuum leack leaning our cam mix can also contribute to higher temp in traffic.
So check this stuff out and get back to us with what your setup is and what you have found thus far.
Scott
