Do I really need this stud? Or, how to remove a helicoil gone bad?

[Inf]

I'm in the process of swapping cylinder heads.

In the farthest forward manifold stud hole on , there is a damaged helicoil insert starting several turns below the surface. It's older than all the other inserts I think. It is damaged to the point that I cannot get a screw in since it has numerous burs within the thread, I think from the threads seizing up around the old stud before someone forced it out. I tried chasing a tap through it but ended up breaking off the tip! barely got the fragments out (bad idea, I know. Didn't realize how hard those inserts are)

1) Do I really need this stud? If I use all the other studs, and just not this one will I have trouble getting a good seal with a 6-2 header?

and/or

2) How can I get the old helicoil out, and would it be futile to try to put a new one in its place? Keep in mind the hole is already drilled out to 21/64 (i believe) for the 8x1.25 insert

[Bambikiller240]

Yes, you do need that stud/bolthole to mount your header/manifold. Without it you will most certainly have an exhaust leak. It may appear to be sealed at first start-up, but it won't take long for the gasket material to get burned out and the leak will grow, and grow.

As for the repair, this type of situation is one where I am not a fan of attempting a home repair. I don't mind drilling out bad threads in an aluminum head and installing a helicoil, but in a case like this one, I would contact a reputable local machine shop and enlist their services to remove the bad helicoil and install an appropriate new one. You may end up with an over-sized stud in that position, but IMO a prefessional has a better shot at making a successful repair than most of us do by trying it at home. You don't want to chance making the situation worse and ruining your cylinder head. There is no substitute for experience in this sort of situation. It should not be too expensive to have this done.

[Ed]

Since you have the head off I too would take it to a machine shop. I had bought a head where the PO obviously tried to do some machine work himself and the drill went the wrong direction. What a mess. I had to have the hole welded, redrilled and retapped.

[ChrisA]

Originally posted by Ed

.....hole welded, redrilled and retapped.

As Ed stated, this is ultimately the best solution if you can afford it. Some machine shops will really gouge a guy, some wont. If you are skilled with a tap, mount the head plumb in a good drill press. Find the next size up stud that will fit in your already enlarged hole and drill and tap the head so you dont need a helicoil. Slow and steady when drilling aluminum. High speed is not what you want. I had access to better quality tools and did two holes this way on my E31 head. Worked good, no leaks.

Much luck,

Chris

[Inf]

Yeah you guys are right, I am taking it up to the machine shop tomorrow. I talked to them on the phone and they told me it shouldnt be a problem. While its up there I guess i'll have them doublecheck the rest of the head before I slap it on my motor

[ChrisA]

Hey Andrew, good luck with the machine work. I found one of the best tools I own is a metric thread chaser/cleaner set. I cleaned every hole on the block and the head and blew them out with compressed air. I know for sure that the bolts will go in nice and come out nice later if needed. A little anti-seize on your studs when you reassemble things will work wonders also.

Much luck,

Chris