51 Rust Bucket,
The carbon content of cast iron is the bug-a-boo! When you weld it and melt the parent metal, the carbon is displaced and ends up right smack dab in the weld zone in the form of Martensite.
Martensite puts Kryptonite to shame on a hardness and brittle scale. Arc welding rods for cast iron are usually 'pulse' rods that sort of turn on and off in an attempt to keep the weld zone as cool as possible. Preheating the casting, welding and postheating allows the carbon atoms to migrate back to where they belong instead of being concentrated in the heat affected zone..HAF.
I have a bench grinder stand at home that someone welded back together with a wire feed and steel wire. It looks like hell but hasn't fallen apart yet...sort of like your cylinder heads. If actual strength of the weld is important, the proper welding procedure must be followed...you can't fool those carbon molecules for long.
Stuart
