Rounded off nut, suggestions?

[gastropodus]

Well, I finally did it... I was out in the sleet today trying to get one final job done on the W201/190D before heading out for time with the family down south. The goal was to get the fuel injectors out to send to C Sean Watts for a rebuild. I might have been able to do it by just loosening the hard lines and pushing them aside, but I've heard bad things about how fragile they are in the later motors. I also need to replace the delivery valve o-rings badly, they're leaking all over the place. So, it made sense to remove the input manifold to get at everything: with that off I can remove the hard lines from both the injector pump and the injectors, and also get at the delivery valves cleanly.

The inboard side of the air filter box is held in place by four nuts, two fore and two aft. They were tight on the front, but I got them out OK. On the back I nearly stripped the top one but bore down on it and it loosened. The last one is down low, and the stud for it comes out from the oil filter canister body; I started out with a 12 point 10mm socket, and I couldn't budge it. I felt the socket give a little, the tell-tale sign of buggering it up. I quickly switched to a six point socket, and tried to budge it. No go, though it rounded some more despite all the force I could put on it. Gave up, went to the store; came back with Liquid Wrench lubricant, freeze spray, a micro butane torch, and a Sears Bolt-Out Plus set. I lubed it, tapped it, froze, heated it, froze it, heated it, and then finally completed the rounding process with the Bolt-Out Plus. The bolt out plus has flutes on it that are supposed to grip the head tighter as you turn it, but in this case the nut is cheap and it just shaved the remaining corners off quite neatly.

So, now that damn rounded nut sits there laughing at me, and I got nothin. I can't get a nut splitter on it, no room. I could buy an extra long chisel, and maybe drive it around. I could buy a grinder and maybe jam it in there to grind one side off. Got any ideas, besides waiting for Spring?

Kurt