Fixing striped threads in head

[tektic]

So while swapping out my lifters a previously heli coiled hole no longer is as such. Problem.

Not only did it pull out of the head but it damaged the dowel in the cap.

So after doing some measurements and talking to my machinist I decided a stud was in order. I did ordered a helicoil kit for good measure, but I'm looking for a m8/m10 stud. I used the same repair for one of my exhaust manifold studs with good results. I considered the time sert but don't think that will work with the dowel.

What I found:
option 1
option 2
option 3

Option 3 seems most promising. VW part N90905502 is a m8x1.25/m10 x1.5 stud that I can cut to the length I need. I'm going to call a local VW dealer and see if they have one in stock tomorrow.

If anyone here is better than I in the way of the Google please point me to what you find.

 

[mitsuturbo]

Time-Sert will fix it. If necessary, go for the 2x version for your desired thread pattern. EDIT: now that i think about it, that probably WOULD screw with where the locating dowel goes. What a PITA.... Good luck.

 

[prove_it]

You should still be able to use a time-sert with the dowel. Basically drop the insert lower than the surface so a dowel can be used.

 

[tektic]

VW will have 5 of these waiting for me tomorrow. But they want my auto repair tax id number... for a part that sells for $2. I didn't want to tell him I didn't have one for fear of him not selling me the part. See what happens I guess.

 

[tektic]

Quoting prove_it:
You should still be able to use a time-sert with the dowel. Basically drop the insert lower than the surface so a dowel can be used.



Does'nt the top of the time-sert have a lip on it? Also anyone know what the approximate tap size for the m8 internal thread?

 

[prove_it]

It does have a lip. This is what sets it. You'll need to counter bore the hole before installing so the time sert will sit farther down in the head. This will allow a dowel to be set on top of the sert. You will need to be very accurate on this so the dowel is fitted snuggly in the bore. If you can find a spare cam cap to use as a guide for the oversize drill bit, I would highly recommend that.

 

[prove_it]

If the stud you have listed will work, that's not a bad choice. My only concern would be that the torque spec could possibly differ between the stud and bolt holding the cap down.

 

[tektic]

Cam cap guide is a good idea.

The FSM only calls for 15 ft lb. With a stud nut and preferred lock washer you think its going to be too loose or tight at that torque?

The hole is jagged and ugly however I have done some tap size comparisons. The stud is bigger than the insert. The major diameter of the insert .381", so for those threads to have puled out the hole is at least this size currently at some parts.

This is still smaller than the minor of the m10x1.25 thread which is 10mm or .394".

Lastly the dowel pin diameter for the cap is also .394" or 10mm. This could be good or bad depending on where I set it. I can possibly just do away with the pin for that side. but looking at the picture again I will probably set it as far down as I can and use the dowel pin as originally intended.

For the stud m10 standard thread tap would be used. Drill size of 11/32 or .344"
For the Time-sert sti thread tap would be used. Drill size of "P" or .323"

Here is the M-tap chart
Here is the Time-Sert chart

Don't mind my rambling. I'm just documenting my notes so I don't loose them, and for anyone else who finds them useful. Can I over analyze sh*t or what!?

 

[prove_it]

I'm the same way sir. You still torque the fastener to the same spec, but I'd put a stud in the other hole. Dunno, but I'd imagine the forces against the cap would be unequal if there is a bolt on one hole and a stud in the other.

I could be over analyzing too.

 

[iceman69510]

Basically torquing is to achieve a clamping force, so they should be the same. But given the different materials and other changes, perhaps some variation.

 

[prove_it]

That's what I wondered. Also given a stud applies the force differently than a bolt would too. Knowing that this engine will be making over 400 crank, makes me wanna say put a stud in both holes to keep the force even.

 

[tektic]

Picked up the studs at Volkswagen and taped the head to accept it. I didnt have a bottoming tap so I cut some the tip off of my m10x.1.5 tap to get in deep enough. The m8 side of the stud was trimmed a little bit too. It looks pretty good, my only issue now is I don't have another dowel sleeve. Anyone have a blown up head and want to make a small donation?
As it sits awaiting a dowel.

 

[tektic]

The new 10m set sleeves came in! Had to chop a thread off the bottom. Used some blue lock tight and it now looks like this.


Also took this tme to clean everything. Under all the caps I found this black goo.


Its pretty amazing that even with ample amounts of assembly lube this stuff devolved while degreeing the cam gears.

 

[thruarod]

I got the same black goo degreeing my cams in recently. Tried assembly lube, oil, cleaning the bolts every single thread.. nothing would stop this goo from showing up. I am hoping that its just a new set of cams and it will stop once its running.

 

[prove_it]

That's why I change oil multiple times after a build.