Mike,

 

It's a bit hard to tell what's up when you rebuild the engine and alter the cooling system at the same time.

 

Often the issue is improper ignition timing.....not enough advance will cause high exhaust temps and subsequent high coolant temps.

 

Not sure on the Nail Head water pumps. The rebuilder could have screwed it up.

 

I have NEVER seen too much coolant flow cause a engine with a pressurized cooling system to run hot. This is an issue with flat head Fords with non-pressurized systems that has become a Hot Rodders Myth.

 

Howard Stewart