Well in Austin you shouldn't need to encounter much corrosion. So once you get the bolt out then you have a decision: helicoil will work and is best if the tighening torque is over about 35 lb-ft and you have enough meat around the hole to drill out.


OTOH if 10-15 lb-ft or you can tap and not much material comes out then I'd probably try torquing down on just a spacer or stack of washers and see what it feels like (and this is a judgement call) If feels solid then I'd probably just go with one of the stainless bolts so they match. If not then choice time: drill and tap to next available size or go with the helicoil route.


I have seen manifolds with a missing bolt and a lot of permatex before and so long as not next to a water or oil passage can work. Personally am more of the "fix properly and use only grease on gaskets" school but then have used a ball pein hammer to make gaskets before.


But the hard part is removing the bolt in the first place and how good the machinest who does is. If it can be removed without drilling through the threads then that is the fist step.


Personally, I still like the "weld a nut" method better since no drilling is required but needs someone who knows what they are doing.



Now if you want a royal pain then try rebuilding a GM Quad-4.

 

A lot of good advice has been given in this thread. Attempting to drill a stainless bolt for a left hand threaded remover will not be fun. If I have part of a bolt sticking up like that, I usually go for the vice grips first. Use a small cutoff wheel to make the slot for the screwdriver if the the vicegrips don't work.

A thread chaser is what you really want, not a thread tap. A tap cuts new threads, and chaser restores damaged threads. I have the set below and use it all the time. I often run a chaser through questionable aluminum or rusty steel threads before reinstalling. Saves many headaches.

If the threads are too far gone, then, yeah, helicoil.

Craftsman 48 pc. SAE & Metric Thread Restorer Kit

 

Thank you everyone for your good advice. I wish I would have asked before and probably wouldn't have this problem. Hopefully once these manifolds are installed they won't have to be removed for a long time. BTW, the recommended torque from Needswings is 10 ft/lbs, so not much.


So stainless steel bolts or black oxide alloy steel. The steel ones are much harder which I'm not sure if that's a good thing or a bad thing. Also don't know which would interact better with the aluminum intake plenum. Aluminum bolts like the stock ones would be best but can't find any in the right size.

 

Well last weekend I got a thread chaser and cleaned out the passenger side mani. There was gunk in the threads. Today I tried drilling on the bolt which didn't go very comfortable so I stopped. Good news is I got everything else put back on and started it. After charging a dead battery. Don't know why that would have happened, just had the hood open. It purred like a kitty, no misses. Don't know if I said but I replaced with one step cooler plugs and magnicore wires.

There was a little smoke at the rear of the engine but I'm guessing that came from the oil from removing the covers. I'll take it to a shop to have the bolt removed.

Attached is a pic for your viewing pleasure. THANK YOU everyone for you help.