i dont know much about breaking engins loos.
but i have broke one loose its in a 1930's aliss tractor it was sitting for around 50 years probly with nothing over the exaust when i got it i bout a can of pb penatrating oil and uesed the hole thing in the cilinder walls and then took a hammer to it and i got it turning a littel but i will try some mystry oil
P.s pb works good also