I've not had much luck with the electric fan solution. Every time I've had cooling issues, it turned out to be something (or combination of things) within the cooling, fuel and/or ignition systems that created the problem. You don't want to add a pusher fan with the mechanical fan left in place; that usually causes more trouble with air flow through the radiator. You could try replacing the mechanical fan with a good (electric) puller fan and shroud, but you really should be able to count on the cooling system working properly with the mechanical fan if this is a "street" engine.
Having the coolant temperature climb to 230F after shutting the engine off is not necessarily a problem. The coolant temperature in the engine WILL increase after shut-down as the latent heat is absorbed by the coolant.
Operating temperatures of 200-210F are not overheating, but it does seem that your operating temperatures should be closer to your thermostat setting and the fuel vaporization problem has to be addressed.
Is the engine consuming coolant? You might have a combustion chamber leak that is heating the coolant. Any evidence of coolant on plugs? Any bubbles in the coolant when you start the engine and watch the coolant in the radiator? That would indicate combustion gases being forced into the cooling system through a bad head gasket, cracked cylinder or head, etc.
Is the carb set up properly? Lean mixtures will generate additional heat.
Pontiac V8s were originally equipped with 195F thermostats. A 180F thermostat usually provides the best balance between quick warm-ups and efficient operating temperatures.
At the operating temperatures you mention, there should be about a 40F temperature drop from the radiator inlet to the radiator outlet. For example, if coolant coming into the radiator from the water outlet/thermostat is 210F, it should be returning to the water pump at about 160-170F. If the temperature gradient is less than that, you either have a flow restriction in the radiator, poor coolant flow from the pump, or poor airflow through the radiator. If the timing is correct and you have an aluminum rad with proper clearance between the divider plate and the impeller, you should see strong flow and a big drop in temperature as the coolant moves through the radiator.
Are you getting adequate flow through the radiator? With the radiator cap off, start the engine and watch the coolant as the engine warms up. You should be able to see evidence of significant coolant flow as the thermostat opens. If not, there is something impeding coolant flow through the water pump, the thermostat, the heater core, the radiator hoses or the radiator.
Are you using a heavy duty fan clutch with an appropriate diameter (I like the 19.5") fan?
Does the fan clutch work properly? At those operating temperatures (approaching 230F), the clutch should be engaging and you should definitely hear the difference when the fan speed increases. The Hayden 2797 is a good choice.
Are you using the proper fan? I've seen people use the wrong pitch and even the wrong rotation fans...
Is the fan blade properly positioned in the shroud? (about 2/3 of the blade inside the shroud and 1/3 of the blade should be rearward of the shroud)
Do the shroud opening and fan diameter match? The fan blades should almost fill the opening in the shroud. There should be about 1" of open space between the edge of the blades and the inside edge of the shroud opening.
Does the shroud fit snugly to the radiator/core support? There should not be room for airflow to get pulled into the fan without going through the radiator.
Maybe you've been through all of this, but in my experience there is usually a combination of factors that contribute to the high operating temperatures and everything has to be right.
1968 Pontiac GTO
1983 Pontiac Bonneville (G) wagon
2008 Pontiac G8 base
Last edited by jmt455; 09-18-2012 at 03:06 PM.
Reason: added comment, X2