Thanks so much guys! This information is so helpful. I think your right about the drill press. I am going to get a good dremel bit that can remove the rest of the bolt and center the hole. The bit I have isnt doing so well against stainless.
I have another question. The tip of the stainless screw seems to be stuck in the bottom of the whole almost like its threaded into the inner exhaust wall. Is this the case or is it just in the port hole?
Its all about timing, dont need to heat the pipe just weld the nut on and wait that perfect 97 seconds or whatever right when the heat has all transferred from the screw to the surrounding heapipe and then attack. Just like icy hot, the hot screw in the cold pipe forces a little clearance then the resulting hot pipe surrounding the cool screw relaxes the pain away.
this is exactly how i would remove the stuck screws. id never drill them out. sooo much more risk damaging the aluminum if youre drilling plus if you break a drill bit or extractor bit off in the screw, then youre really fricked. also the very bottom of the screw goes into a small pocket machined into the water jacket of the headpipe so the hole can be sealed. corrosion can build up there so if you dont properly heat the headpipe, youll never get it out.
I payed a friend at his machine shop to do this. Its pretty perfect. The hole is large but I think an oversized helicoil will solve the problem.
As far as the others I am going to heat them up and use an extractor for one and a allen tool for the other.
Also I have no idea how you would weld to the top of that stripped allen head, sure you could grind it flat and it wont weld to the aluminum but how does that give it strength if your welding at an angle with a tig welder and a weak ass stainless rod
Use a slightly larger nut and weld it to the stainless. The weld wont stick to the aluminum. Once welded, allow to cool for a short time then hot the top with a hammer several times while still hot. That will break.loose the corrosion. Then slowly back the screw out. I've seen this work several times and work flawlessly each time. Doesnt matter If the bolt is broken off flush or not. Last time I've used this method was removing heavily corroded starter mounting bolts on 62t cases. Took a while and had to reweld the nut on a few times but it did break free.
I wanted to give a final update on what I did for other peoples future help. Long story short welding to the bolt is the best way to remove them. I took it to my local welder and he said he had a "tool" for this. He welded a rod to it instead of a bolt and said he had a tool that grabbed the rod for extraction instead. He said he does it all the time and often the threads get ripped out with the bolt because its so corroded. In my case the threads were intact but I wasn't going to use them anyway because I already bought the oversize kit.
I already had a complete oversize kit so I was just going to use all three bolts it came with. I drilled out the two good holes with a drill gun and it seemed to go well. BUT when I threaded in the bolt it was off by a hair. I dont know if there is any real way to do a better job of this. It works, it just bumps the side of the port before pushing past. I didn't trust the original threads, the aluminum was SO soft and quite corroded. If you can get your hands on the original size bolts I would actually recommend just using those original threads because when I went and tested the ports you can tell the bolt didn't seat that well. One of them wouldn't turn off all the way and the adjust-ability was pretty poor. The only way to get a perfect fit is with original threads.
And as far as the one I drilled out and repaired, that was a long journey. First I had a machine shop drill a large hole as well as they could and it looked great but it ended up being off by small bit too. I was going to use a thread insert but when I saw it was off I just had it welded shut. Before I welded it shut how ever I made marks so I knew exactly where the port was. When I got it back from the welder I made a mark with a punch and drilled the hole with a drill gun. The hole ended up being spot on but a just a millimeter crooked. It ended up working because I enlarged the shoulder on the port so the pin would pop in. The welding idea was great, definitely way better than an insert. Plus I can re-weld it if I mess it up.
I was about to install the pipe and then I decided to test it. Good thing I did because none of the ports were working well. One was clogged up and the others were spraying a bit too much. ALSO the threads were leaking water pretty bad... That I did not expect, so I put thread tape on them and it only stopped leaking when I tightened the retaining nut. Plus I found one of the ports wouldn't shut off no matter what, almost but not all the way. That's good to know.
A thought that just occurred to me, instead of welding up that oversized hole and redrilling you could have held the screw in place and inline with the port, and filled around it with aluminum braze. I've done it on other projects, you basically cast new threads around the screw and in this case it would have saved trying to re drill and tap the hole back on center with the port.
On most automotive/pwc applications you typically don't want to use thread tape since it can plug passages up if it gets loose. Use a liquid thread sealant instead.
I had this happen on an oil pressure sending unit on my 15f motor, fortunately it was just for a gauge but some tape got loose and lodged in the pressure port. I only found it because the gauge showed pressure when the engine wasn't running. When I pulled the sending unit off and pulled the teflon tape out I got squirted in the face by the pressurized oil stuck in the sending unit...