Ideally, you'd build the material back up and re-drill and tap. Here's one way:


The first part of this video shows how to repair threads by casting new ones with HTS-2000 brazing rod.

 

There are also some thread restore products that coat the bolt with "release" agent, pour goop in hole, screw in bolt, cure, back it out, use new clean bolt. But the ones carried by Grainger say not for automotive. Guess the heat cycles get involved. But maybe a good idea.

The HTS method would require heating the head to flow in the material. It is the forth bolt hole back, so in the middle of the head. Warp what I just milled?

But thanks, and I'll check it out.

 

Measure the depth of the now stripped holes in the heads without the Helicoil. I would go with metric bolts and Helicoil back to original metric bolt size/thread.

Not close enough for me, almost two full threads shorter.

The one with the stripped out Helicoil you've no choice but to go larger either by tap or another Helicoil.

Here's what I'd do because I'm me;

I'd have a blind tap, grind off enough of the end to hit hole bottom with tap thread, leave just enough to start cutting without it being too shallow or too excessive so I can thread new bolt all the way down to very near the bottom. Now I grind between the flutes of the tap to clear an area for the chips to pile once I'm near bottom (blowing out until near bottom of course). I'd grind a what looks like an "X" joining flute valleys on the very tip of my tap. I'd get myself metric Helicoils and if I can't find the longer ones I'd use two and flush cut with a cutoff wheel the excess sticking up above the head surface. I'd buy longer metric bolts, same size as original except for the one Helicoil that stripped. That would be next size up metric Helicoil. I'd be good to go with the original spec of 28 ft/lbs. I'd use Loctite blue to lock them with and be done.

Now I have a ton of patience and a ton of experience in the machine tool/machine tool electrical world. I also have a ton of experience fixing my own screw-ups so I'm very well trained. It's so much easier to take the time one time instead of taking extra time twice and three times, always being in a hurry and having a lousy time of it......

I know your under pressure to complete and you want to fire up the beast to see the fruits of your labor but you've got to think this out, plan this fix out so your not revisiting it again.....ever. If you don't understand what I'm saying ask me because I have a tendency to type slower than I think. 60 WPM is way too slow.

 

Well, let's talk.

What came out of there is 3/8 - 16, not metric. At least that is what they thread into on the bolt display stand at the parts counter. So is that a problem to start with? If they are not really 3/8 - 16, that opens up more problems, as that is the size tap I used to clear the other holes.

The short boilts (there are ten of them) will screw in flush if the intake manifold is not present. So no way with the intake on there that they are bottoming out.

The half length helicoil made it to 40 newton meters. So could I infer that with only half of the threads touching anything it made to 40 nm? If so, would two threads missing, and me going to a lower target torque using all the threads really make a difference?

Went by the store that sold me the helicoil, they have smaller diamters in stock. But no longer ones. So, with the hole that is tapped for heliucoil all the way, but pulled out smooth on the top section, could I stack two short coils and have anything more than a prayer of it working? Also, is this something I can test with a stack of washers before putting the intake on? Assuming if it works, it should work a second time. The bolts that hold the intake on enter the head at some angle off from 90 degrees.

I'm under the shade tree, and have no vise, bench grinder, or CNC gear available. While I believe I could follow your instructions and eventually get something that would work, I suspect I would have a number of trial and error things. Don't have a lot of experimentation left with the head. I suspect if not "easy" to fix the intake issue, I'll be forced to order more head bolts, pull the head, and head over to the machine shop. Some one with a drill press and other tools may have a bit more chance for success than I will with a Black and Decker 3/8 drill.

At least the questionable bolt hole in next to a cylinder intake, not the water channel. Maybe a little torque and a little RTV.

But those guys in the outback 700 miles from a dealer can do this, as the guys in the bush of Kenya.

 

I'd check em again for sure. Try 10 1.5 metric to be sure, they're .5mm larger than 3/8". I frankly don't have any idea, I've never had to check in almost 2 dozen hg jobs.....

Besides the higher torque on somewhat short bolts it might be the problem. I don't see any other reason for them stripping out in the first place. I won't remove mine since they are thread locked but if someone wants to to help out that would be cool.

So you have 10 chances at longer bolts by say a 1/4", that would be enough to clamp the manifold down. The other two a solution can be worked out, like doubling the helicoils or something like that. My fear is that if you go larger diameter and there's another problem then what?

 

I looked up the bolt part numbers and the short ones come up as 3/8, so that is better.

So you are saying that maybe my 10 stripped out holes are stripped out only partly and a longer bolt with no other work may hold?

I am concerned that if I helicoil all of them I have myself at a point of no alternatives like you say.

I suspect they stripped because I'm stupid, because I cleaned out the threads with a tap (rather than a gun cleaning brush), and becuase I used the 51 NM torque rather than the 38 NM torque. And because I'm stupid.

So I'll be going to 28 foot pounds this time.

 

is there any way to epoxy a stud in that one hole and still drop the intake on?

 

That could be done. And I'm re-thinking the 7/16 bolts because if I had gasket alignment problems with 3/8ths, I can't imagine them getting better with less wiggle room. The gasket holes are 7/16.

 

for what its worth, I have had better luck with the epoxy stud method. unfortunately, I have had several occasions to use variations of the epoxy stud and jb weld/re-tap methods. the jb method has only proven successful, to me, when current threads are present. when tapping to a smaller diameter hole. Then, the threads provide enough of a mechanical tooth for sufficient bonding and it works fine. without threads, I have experienced failure with that technique.

 

Your tired, don't have time and you assumed your information was correct. So you made a mistake, big deal. If worse comes to worse at one time Will Tillery was offering rebuilt heads for $100 a piece. Will Tillery Parts for Land Rovers. The "Roverguy" of new and used parts!

Check these out Full-Torque, Permanent Thread Replacement