Technical White buildup in water jacket

Pulled my intake manifold on a SBC and furthest back two water jacket ports both have a buildup of white crust blocking the flow. What could cause this? Is pulling the head the best way to clean out this buildup?

 

Corrosion from the aluminum and iron. This happens when sitting and allowing electrolysis to happen.

Keep better control of your ph balance if your not heat cycling the motor very much.
Chances are you also have some corrosion issues starting in your radiator as well.


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Dex Cool. Jk.
But the old dex cool from the 90's was seriously bad stuff.

 

does that intake have anywhere for the coolant to go, in the manifold? or is it a dead end? If it's a 1969 intake, it's a dead end.

 

Refer to this thread https://www.jalopyjournal.com/forum...g-where-they-shouldnt-be.652529/#post-7238051

 

Pretty normal in old engines, is the intake and or radiator aluminum? I have a lot of aluminum parts on my 355 and use a sacrificial anode in the drain port of my radiator so the electrolysis has a place to collect.