This just recently happened. The car will overheat steadily to 250* (I usually shut it off at 240). It overheated in traffic and on the highway and I can't explain why. I pulled the t-stat, still overheats, changed the water pump, still overheats, flushed the entire system and ran it with clean water going through it, still overheats. I run dex-cool in the system and have done this for over a year, car always ran around 160* with dexcool in it, even in traffic and in the middle of summer. I never had an air dam on the car (it was missing since I bought it) and never had a problem with cooling so that isn't an option. Its not the cooling fans because they are wired up to an independent switch and are not computer controlled. they are always on as soon as the car is started. I recently got all the "bugs" out of the cam/head swap I did and this appears to be a symptom of it. its none of the causes for standard overheating problems (tstat, waterpump, fans, leaks, etc.). When the car wasn't running right it wasn't over heating, now that it runs right it is... I know strange. I think the timing is off quite a bit though (as in very advance). could this cause significant overheating problems? there is no head gasket leak or anything like that. If everything else fails I'm upgrading to a 3-core radiator. of course if this doesn't solve the problem I don't know what will. Any ideas. I'm looking for the extraneous here since nothing else is adding up.

 

I had the same problem when i swapped out my v6 for a 305. I got the engine and radiator from the same car that was wrecked. No leaks anywhere, changed thermo 2 times, replaced waterpump and also have a manual electric fan. Funny thing too is that I never had an air dam on the car since purchase.

Thats the only thing that I can think of, putting one on there. I have one sitting around, as soon as I get it on, Ill let ya know what happened with it.

 

yes, timing can play a factor in overheating. and so can not having that air dam on the car, even if it worked before. but the air dam plays more of a factor when driving at speed, not idling or in slower city traffic.
any time you make major engine changes, you need to start back at square one and not assume that just because it worked right before it will work right now.

 

I would check your timing as he said... Being overly advanced will cause an overheating condition...