I was going to do the standard fix, which seems to be to tap out a 7/16-20 hole, and make new studs out of all thread. But apparently the previous owner(s) have decided I'm not going to do that.

 

The holes are already larger than 7/16-20. I have 2 of them that have an M12/M10x1.50(I think) studs, 1 with an M10x1.00 bolt, and 1 that is possible factory(the stud remains in the head, the nut came off).

 

What is the best route to fix this now? Heli-coil? Or something else? The M12 studs have the nuts frozen on(on the M10 side), and they are a little large for the exhaust gasket(they actually have to be threaded through the gasket bolt hole).

Edited January 5, 201115 yr by Speedwagon

Well, if someone hogged out the holes larger that 7/16", you're to big to coil it. Your best bet at this point is to drill the other two stud bosses on each head to the correct size for a 10x1.25 helicoil, install the coil into the fresh hole. DO NOT drill and install the stud by itself without the coil. It'll just pull out later anyways. DO NOT use all thread for anything exhaust. It's not strong enough. After you've got the studs in, you'll have to cut the Y-pipe flange off each side, rotate it 90 degrees and weld it back on. Use stainless steel nuts with lock washers. It won't come loose, and it won't be frozen next time you need to take it off.

Well, if someone hogged out the holes larger that 7/16", you're to big to coil it. Your best bet at this point is to drill the other two stud bosses on each head to the correct size for a 10x1.25 helicoil, install the coil into the fresh hole. DO NOT drill and install the stud by itself without the coil. It'll just pull out later anyways. DO NOT use all thread for anything exhaust. It's not strong enough. After you've got the studs in, you'll have to cut the Y-pipe flange off each side, rotate it 90 degrees and weld it back on. Use stainless steel nuts with lock washers. It won't come loose, and it won't be frozen next time you need to take it off.

 

I burned up 3 saw blades trying to cut this all thread. I had to resort to a cutting disc to get through it. I doubt the all thread I got is anywhere close to weak.

It's your rig, but I've been at this game since I was 8, and I'm telling you that you don't want to use all thread on exhaust. You want (near) future problems, be my guest.....

You can buy 10x1.25 studs in the "HELP" brand at most auto stores. there is a pair of studs, and you can also get the GM/Toyota stud and bolt kits(toyota corolla/gep prism) This will supply you with 3 studs and 2 bolts if the first kit is not available.

 

I would explore what it takes to do a helicoil. Do not drill all the way thru the hole or it will poke thru the casting