I was changing out my starter on my 1983 240D. Everything was going smoothly until the last, top 10mm allen-head bolt. It would not budge. I used a 10 mm allen head socket with a cheater bar and it would not budge and began to strip out. It actually felt like the socket would snap if I tried any harder. I soaked the area with penetrating oil and was working with a cool enginge. Would it be better with a hot engine? Would hitting the bolt with a torch help or cause more damage? I saw the idea of valve lapping compound but I think I am beyond that stage. There is some room between the fire wall and the bolt, but the room is limited. HELP?

Darryn