Normally I agree, but this is a steel bolt in an aluminum cylinder head. The aluminum will expand at a faster rate than the steel bolt and it should come right out. I'd bet the tractor stuff is all steel on steel.Try and heat the area, not the bolt. Metal expands when hot so you don't want to expand the bolt, you want the bolt hole to expand.
I work at a tractor salvage yard and taking out (big) siezed bolts is a common issue. Heat with torches is the best way.