Question(s) about cast iron cores for water/coolant

[71CHEVYSHORTBED402]

I had this blasted with some things. It might be the original housing off my 71 402, not sure. Could have been new to the truck in Feb. 1993 to be exact, when the engine was rebuilt.

I'd like to replace the clone smooth surface housing with this cast iron piece. Think I'll paint it with por15 engine orange, and a sponge brush - works well on cast iron, especially small stuff.

Got me wondering about core finishes, the interior surface was pretty corroded before it was blasted.

Let me guess, the factory "sprayed" the interiors with the top coat, or something else not expected to last....I really don't know, perhaps they figure corrosion protection in coolants good enough - not sure, so I'm asking.

That, and how would you finish the interior, if anything?

With a green observation, seems cast iron holds up up well to water, hot even better. Perhaps cores were hit with something temporary, for rust prevention during storage, hmm.

[72c20customcamper]

Corrosion happens when the antifreeze is old. The corrosion inhibitors are used up over time .

[Getter-Done]

I use this on the inside of tractor cases that I have restored.

https://www.amazon.com/Glyptal-Brush...30737255&psc=1

I don't know if it is Anti-freeze resistant ,But I bet it is.
What do you think?

[70STOVEBOLT]

The cast iron water neck would have been stock on the 402. If you are worried about the inner surface, you should think about the block as well. Personally, I think if the coolant is kept up to snuff, the corrosion inhibitors will do the job, nothing else needed.

[Steeveedee]

^ Yup.

[71CHEVYSHORTBED402]

Originally Posted by Getter-Done

I use this on the inside of tractor cases that I have restored.

https://www.amazon.com/Glyptal-Brush...30737255&psc=1

I don't know if it is Anti-freeze resistant ,But I bet it is.
What do you think?

Could be, pull it off and see I can't see where it's heat resistant, but doesn't mean it's not.

Originally Posted by 72c20customcamper

Corrosion happens when the antifreeze is old. The corrosion inhibitors are used up over time .

Makes sense to me. Can't speak for before the 90sish, I always used distilled with conventional, and changed it often. The housing was pretty bad, but other water ports looked good with the manifold, water pump and hoses off, just some white residue. With a dry system and new OER parts, I switched to ACDelco 10-5027, it's not conventional, different corrosion protection than conventional, but does have one common ingredient. One place sells it at not even half the cost everywhere else. I think it goes five years, but I'll probably drain and replenish every couple years. Definitely a clean system, I should know, had to replace the radiator three times before one suited, and even that was *(&*&)(^-up because they positioned the fill off acceptable. I was floored; they said they'd send one for my fourth shot at it (three theirs), but (*)^ it, doesn't leak and nice appearance. COVID mentality, at over 1K per radiator.

Originally Posted by 70STOVEBOLT

The cast iron water neck would have been stock on the 402. If you are worried about the inner surface, you should think about the block as well. Personally, I think if the coolant is kept up to snuff, the corrosion inhibitors will do the job, nothing else needed.

I'll run with that, thanks.