Torch is the best, but if you insist on not using one then attempt to break them loose with PB Blaster,let dry for 15 minutes, then tap the bolt
head continuously for 5 minutes with a ballpeen hammer. Repeat this cycle at least 5 times. Then use wrench and attempt to tighten bolt, then attempt to loosen, but not enough pressure to strip it. If she doesnt move, keep tapping. Got four
head bolts off 40 year old Cat
diesel using this method, just took all day sunrise to sunset !!