[Mustard72]

I asked one of the maintenance guys at work about the reduced coolant passages. He thought they were to restrict the flow when the thermostat opens up to prevent a gush of colder coolant from rushing to the hot head and increasing the likelyhood of warpage. Makes sense, I suppose. I guess if you were only running in the summer and didn't run the thermostat, a larger opening wouldn't hurt, but I don't think I'll mess with them for my truck.

I've also read/heard about some of the phenomena mentioned in that bit above from JP about water/coolant flowing too fast through a radiator (or any heat exchanger, for that matter) and reduicing it's effectiveness. I think there's some merit to that.