Thinking of replacing water pump on my 1973 351 H code as preventive maintenance in hot Florida summer. Would like to go with a standard flow aluminum water pump for weight savings and looks but was wondering about galvanic reaction of mixing aluminum onto cast iron engine block. Any experience with this?
It will be fine, especially if you have a gasket under it. Plus, antifreeze has rust inhibitor in it. If you’re really worried about it put some antiseize compound on the bolts.
Aluminum and cast iron have very similar galvanic numbers, hence they tend not to cause any problem with one another provided that you keep an appropriate anti freeze / water mixture in the engine at all times.
On the outside of the engine bare aluminum will corrode. Appearance wise that is not too attractive. You might consider painting the aluminum pump.
I recommend using a good clear engine paint if you are looking for the aluminum look. It will dull it down some. But still look nice. Or paint it the same as the block to hide it some. I did that with the Elldelbrock intake on my White 70.