Wouldn't most of the heat generated be up in the cylinder head? When you fire up an engine the cylinder heads get warm far faster than the block and there is coolant in both places.

I used to have a 350 in my truck that ran always ran hot. I used the parts store type water pumps and always figured it ran hot because I was told the engine was bored .060 when I bought it. I have since replaced that engine with a 400 small block. I took the heads off the old 350 the other day and it was only .030 over. So much for that excuse.

On the new 400 I built I was warned by several people that those engines can't be kept cool on the street because they are a siamese bore block. I had no experiance with them, but knew I didn't want to build another 350 so I ended up buying an edlebrock water pump as I was told they really work wonders. Needless to say the 400 runs cooler than the 350 ever did. I think my 350 ran hot just because the stock style water pumps are barely capable of cooling a stock engine. Add a cam, headers, etc and you are pushing your luck.

The edlebrock pumps have huge curved blades and no extra space within the pump cavity. Every bit of fluid that enters is pushed out the other side. The edelbrock pump works by moving as much fluid as possible.