427 runs too hot

[Jerry Clayton]

pretty March under drive pulleys only work in March---by April its too warm out----

Seriously, underdrive pulleys are for high rpm systems to slow down alternator and waterpump speeds OR to save Horsepower on a short run like possibly drag strip

You have listed about every NO NO that is possible ----underdrive pulleys , small 16 non shrouded fan, non shrouded radiator, but does have a Kirkham expansion tank

[jwoodard]

Go to standard size pulleys and shroud both the fan and the radiator. It will make a considerable difference in your idle temperatures.

[BDR879]

Worked through the same issues myself. I'm running a 428FE and now have the Zirgo 3000 CFM fan and a larger radiator with a shroud and running 90-95 deg C on a 100F day.

I also had the engine dyno'd and found out it was set up wrong out of the box. Re-tuning dropped the engine temp by 40 deg F and is now spot on with A/F ratio, etc.

[jhv48]

Thermostat is stuck closed.

[elmariachi]

Originally Posted by Jerry Clayton

You have listed about every NO NO that is possible ----underdrive pulleys , small 16 non shrouded fan, non shrouded radiator, but does have a Kirkham expansion tank

Agreed. That Zirgo may have been advertised at 3000 cfm but its likely not delivering that. After two Zirgo fans, 50/50 coolant mixtures, timing adjustments, Water Wetter, three boutique thermostats and every other method of voodoo blah blah blah it was the $50 eBay Taurus fan that solved ALL of my 427's cooling problems. The quickest way to confirm its your fan is to buy a little handheld infrared temp gun and compare your radiator inlet temps with your outlet temps. If you aren't getting at least a 35+ degree differential at idle, you aren't getting enough air across the radiator.

Just my 2 cents....