Lots of things to try and look for on our cars. See my list below. Some easy and some not so easy. For our birds I would start with HD clutch fan since you have the issue at idle. Make sure you have the shroud in place too. At the some time I would also clearance the WP divider plate. Lots of post on this one over at the PY site.
The 350 cars didn't have the bat wing baffles on top, (not sure the correct name) but it doesn't mean you can't add them. That and the rubber diverts that force the air flow threw the radiator instead of around the radiator.
One thing that I will say about the HD clutch fans. They will move some air. Growing up on the farm and pulling into a gravel driveway you will get a nice plume of dust under the car on a dry day just from the air flow. You don't get this from an electric fan.
*Clogged/Dirty Radiator not flowing properly - radiator flush *Collapsed hoses (needs a spring). * Blow-by finding it way into coolant->Causes foaming->drastically reduces heat transfer (Do a Pressure Test) Blown head gasket for example. *Divider plate clearance appropriately *Test thermostat in boiling water *Air pockets? Drill 1/4 hole in thermostat to pass air pockets. *Type of impeller - Cast is always better and not all cast impellers are the same some are deeper then others. *Fan shroud in place? air dams in place? baffles in place? Fan clearance around fan shroud *Temp infrared gun can be a great troubleshooting tool- compare input temp to output temps of the radiator and look for cool spots or hot spots. Can be used to compare accuracy of gauge/Sender. *faulty gauge - A second gauge check is always a good idea *clutch Flex or Electric - Its tough to beat a good factory 7 blade with HD clutch. *If electric - is your fan a puller or pusher? pusher fans are not good ,they also block radiator *rich or lean carb setting. *Vacuum leaks cause lean conditions Carb bolted down? Orange intake alignment pieces? *timing issue - Try simply backoff on the timing and see what happens *Over heating at idle or driving - Generally If at idle or very low speed, then it is likely an airflow problem. If at speed, then it is likely a coolant flow issue *Retarded cam - Cam not degreed in correctly on ILC. Read about this more then once. *WP pulley diameter for trouble shooting *deck height - Piston down in the hole makes for bad quench. *8 relief pistons notorious for ping and heat related issues. *Clutch fan test. Cold should spin 3 times or more when you shut off the motor. Hot should spin less then 3. *Adjust Clutch fan for max friction.
A lean air/Fuel Ratio (Also check fuel pump and Filter) Too much timing/retarded timin/advanced curve malfunction Clogged Radiator/Collapsed Hose (restricted water flow) Clogged Engine (restricted water flow) Stuck Thermostat / Incorect Thermostat Bad Water Pump Incorrect Water Pump Speed (too slow/too fast)
Radiator Too Thick Wrong Pressure Cap No Shroud Around Fan. Improper Fan Position Within Shroud. Bad Fan Design - Stock Factory Type Usually Works Best. High Volume or High Pressure Oil Pump Electric Fan (Pullers/Pushers) Blocking Air Flow Too Much Antifreeze Wrong Type Antifreeze Flow Test: Begin with cool engine. Remove radiator cap. Start engine. Bring engine up to operating temperature so that the thermostat opens. Increase engine speed to 2000 rpm. If water gushes out of radiator there is a flow restrictionin the system. This must be corrected for proper cooling. Wrong Spark Plugs (ie. Heat Range) Wrong Gasoline Type (Try 89 or 92 Octane) Clogged Catalytic Converter. Clogged Injector System. Exhaust getting into the water due to a cracked head or blown head gasket. Have your local radiator shop test your system for carbon dioxide.
