Stripped Head to Manifold studs

[Xero_Tolerance]

Ok, I searched and found a little bit of information but none of the threads ended up saying what the person posting actually did in the end, so I gotta ask...

I don't know how or why but when I installed my turbo and I was taking off the manifold three of the studs came out with the threads wrapped around em :thumbdown . So I am in the position where I have to re-tap to a bigger size, I guess 10mm would be the next one up since I don't know anywhere that have 9s, or I could try and helicoil the holes. I'm new to both processes of tapping and helicoil so which would you guys suggest for my situation? If I go to a bigger size then I guess I'll have to enlarge the hole in the manifold which will be a bi*** but not impossible since I have a dremel... So anyway, any info on either process would be great, thanks.

 

[BUCK]

First of all remember that the Upper Center Exhaust Manifold Stud Hole is a THRU hole that goes into the Oil Galley - There ARE 9MM Taps, you'll need a Starter & a Bottom Tap - go SLOWLY , remove Tap & blow the holes out with something as you go deeper - But I would try the very closest next size up American Coarse Thread - 5/16 UNC would be my guess - much stronger than any Metric Thread, you'll need Heat Treated Studs too.

 

[GTM]

First of all remember that the Upper Center Exhaust Manifold Stud Hole is a THRU hole that goes into the Oil Galley - There ARE 9MM Taps, you'll need a Starter & a Bottom Tap - go SLOWLY , remove Tap & blow the holes out with something as you go deeper - But I would try the very closest next size up American Coarse Thread - 5/16 UNC would be my guess - much stronger than any Metric Thread, you'll need Heat Treated Studs too.

Actually exhaust studs are made from much the same metal and properties of head bolts. They may also be forged and will have rolled threads rather than cut threads.

With much of the auto industry having converted to metric they shouldn't be that hard to find. A better repair would be to use an insert. These can be found under the names Keensert, Slimsert, and new player on the block is Timesert. They are essentially a thin sleeve threaded on the outside and threaded on the inside, most desirable is to use one which doesn't require special drills, taps, and installing tool. You can also find them in a thicker wall and can convert from SAE to metric or the reverse.

The first two names meet Mil Spec but have not seen any mention of same for Timesert. Their original development was for the Aero Space industry when some threaded item would become damaged and they couldn't replace the part for less than $5 million. Cost of the insert $2-$4 depending on size and special applications. It has been my prefered method of repairing damaged threads for almost 40 years.

Cheers,
GTM