Other than a new head gasket? If you have to remove the head to use some sort of sealer anyway why not use a new gasket? What engine are we talking about here?
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Archie
Irish Lady
1984 Monk 36 Hull #46
Currently in Cape May, NJ
I have not been in your situation, but I've had good luck with Permatex products for most of my gasket sealant needs over the years: https://www.permatex.com/?s=head+gasket
A head gasket leak that is leaking combustion gasses has to be fixed immediately.
I once was slow fixing a leak on a Yanmar diesel and it ate into the cast iron head.
It was an expensive lesson for a new (at the time) boater.