i have a newly rebuilt 440 that is putting out 511 hp and just under 600 ft lbs of torque, the only problem is that it will not stay cool.  sitting at and idle after about 10-15 minutes she's up to 220.  i have an aluminum radiator with an electric fan that turns on when i turn the ignition and stays on. should i put another fan on the radiator or what?!?  

Your motor sounds pretty similar to mine...528 hp and around 580 on torque.  I run two sixteen inch electric fans with no belt driven fan.  Each fan generates 3000 cfm of air.  I also run an aluminum crossflow radiator with no thermostat.  I dont have any cooling problems.  I got both my fans from Summit for $120.00 each.  Part number is HFM-ZFBC16S.  Hope this helps.  Tell me more about your motor, Im interested in what you have.  Good luck!  

thanks for the help. we'll give it a try and let you know if it works or not.  

thanks.we actually now have 3 fans on the car. we have two eight inch fans vertically puling on the one side of teh radiator and one 14 inch fand pushing on the other side of the radiator.  we even cut holes in the hood under the hood scoops to blow some engine heat out of the car. the weather has been in the high 90's the past few days and she's stayed b/w  190 and 200....by the way, we have this motor in a 70 duster. right now we have a 4:30 gear in the rear and that is way two much.  we are going to drop it down to a 4:10.  we have a new manual valve body automatic transmission built by mancini racing. the only thing we still need to do is to put bigger tires on the back. right now it only has regular street tires and it spins like crazy.  

I had the same problem also and I'll tell you to be prepared to spend on a GOOD electric fan or expect more over heating. On the cheap a 19' stainless flex fan w/alum 1 1/4 cross flow radiator fixed my issues.
But first make sure it's not something else going on like timing, bad water pump, ect.  

thanks, the engine certainly runs cooler than it did but still is too hot. when i let the engine idle the car wont get over 160, but soon as i start moving we can watch the gauge creep up. after about 10 mins driving she is up to about 200. but as soon as i let it idle again the temperature will start to drop.(that is with a 160 degree thermostat). i tried taking off the thermostat but it was actually worse. is there anything else i can do to make this engine run cooler or is this where it is just going to run?  

compression?  

I will assume you have a trans. cooler on this vehicle. Check and make sure your trans. cooler isn't blowing excessive heat onto your rad. I had this problem and corrected it by installing a B&M 4 quart trans. pan, the engine temp actually dropped by 20 degrees due to the drop in trans. temp.  
Summit sells a high flow 160 thermostat.
Destilled water which you can purchase in a grocery store disipates heat better than anti-freeze.
The large flex fan is a good idea, personally I run an 18" flex fan, when the clutch in gauges it will cool just about anything. I also run a electric fan that pushes on the other side of the rad for when I am at the track.  
good luck.  

I'll try repositioning the trans cooler and buying distilled water.  Would you suggest using 40 below also?  I am also using a 16 lb. cap is this too much?

Thanks  

13 lb cap would be plenty, the more pressure the more chance of causing a leak.
I have used royal purple water wetter, it made a small difference.