I came across a newly rebuilt 440 that was placed in a car for 12 years and barely driven - less than 100 miles. They lost interest in the project and passed it along to me. Problem is they installed an aluminum radiator in it with the wrong type of coolant so it looks like some electrolysis has been going on for the last 12 years. I'm dissembling and inspecting the motor and have found the treads on the iron water pump housing are pretty brittle and corroded so I'm replacing the housing. I also found the steel freeze plugs have been literally eaten through. The water jackets on the block and heads appear perfectly clean with no signs of corrosion. Can anyone tell me in there are certain spots within the block and heads that would be most affected by this? I don't want to overlook anything when reassembling the motor. Thanks

Welcome aboard. You could have the block pressure checked. I ain't sayin that it is needed but it's an option & you might at least check what your shop would want for that. Otherwise I would start with a good visual which you are doing.

All currently available coolants, for the last several decades, have been compatible with aluminum. Incorrect mixing ratios and depletion of the additives package is what causes the corrosion.

I had a considerable amount of electrolysis going on with a fresh build. I verified this with both a volt meter( one end in the coolant and one on ground), and a visual observation of rapid aluminum corroding with a whitish buildup on aluminum parts..

I was running reverse osmosis water with Redline Water Wetter and 50% anti freeze.

I bought and installed a radiator cap with a sacrificial anode connected with a short length of cable. The electrolysis completely stopped in about 4 days, as verified by the voltage dropping to zero, and the cessation of any corrosion build up on my aluminum parts. I didn't expect such a dramatic result, but t .he cooling system has remained looking clean and corrosion free for several years now. There is also a noticible consumption of the sacrificial anode on the cap.

I run a factory style radiator, an aluminum water pump housing and aluminum heads.

Poor grounding will cause that fast a corrosion issue.

I got concerned about the corrosion issue some years back on the racecar...
$$$ Alum heads, intake, radiator, ft cover.
Always ran distilled water, Water Wetter, and a tiny bit of antifreeze.
Dangled the sacrificial anode in the radiator during the winter months.
Almost nothing on the anode.

I must accidentally be doing something right, I guess.

If I were the OP, I'd have that block cleaned like crazy, but I'm a bit mystified at the goop he found.