ARP install number 10.. and issue with the last one

Well looking for some feedback here. I was installing my 10th headstud kit on an AHU today and on the last bolt swap I was at 110ftlbs and the stud popped the threads out of the block! I couldn't believe it that cylinder 1 rear outer bolt would do that. I presume there was prior underlying issues with it as both the old bolt and the arp stud had no indications of problems. The only thing I can deduce is maybe the block itself had a bad or partial thread install.

anyways, on to the fix options!


All fixes that I am finding look like they need to have the head removed, Something I was hoping to avoid considering the fresh turbo and all new gaskets. The two main kit types I see are:
www.timesert.com
www.helicoil.in/index.htm

Has anyone had any luck with either and holding 28psi?

any other kits or suggestions?

I believe they are m12x1.5 pitch?

I would bore it precisely and cut the next thread dimension and use a custom stud instead of bolt 14x1.25 or 14x1.5
Dont know exactly if arp has studs with 2 different dimensions

yeah that is an option too.. I am going to call ARP today to see what options they have. Anyone around richmond VA have a magdrill? I need to find someone with one so I can avoid dropping the whole motor... boy this project just got really big.

I would make a custom stud but I can understand if that seems like too much hassle.
It would be possible to step up to 1/2-20 thread but that only gives you .028"
thread engagement - not optimum.

For M14 x 2.0 the recommended drill size is 12mm so no drilling needed.
For M14 x 1.5 the recommended drill size is 12.5mm so only .5mm bigger than it is now.
I think I would use a hand held drill motor with a 12mm first to clear out the hole.
Then see if you can step up with a 31/64" and then the 12.5mm drill.
Cast iron is pretty nice to work with but obviously use sharp tools and correct speeds.

Thanks for the feedback guys. I have three options at this point:

1) New block or weld and drill current block
2) Install a bigger ARP bolt... AZQ-5.475-1B 14mmx2.0 bolts $12.46 ea
3) Install a time-sert into the block. https://www.amazon.com/TIME-SERT-Metric-Kit-Part-1215/dp/B001JK44D4/ref=cm_cr_arp_d_product_top?ie=UTF8

I'm trying to figure out if I can do this in engine bay, and think the best way to do it is with a mag based drill. That will allow the straightest drilling possible with relation to the deck. If I can I may take the chance on the time-sert as it looks like one other person has done it on an old 81' 1.6 diesel.

A few discussions with my other engineering friends have us thinking the causal factors are as follows:

-the bolt threads wasn't sufficient from factory for ARP torque values
-the block metal is softer in that area than normal
-there was prior work and damage to that thread.

We ruled out damage due to my installation although my torque wrench hasn't been calibrated recently, and I did notice when installing the bolt by hand with the allen key it was a little rough. It just doesn't seam likely I could have prevented the error by changing what I did.

One more thought. IF going to a stronger bolt in that one location will mean more load on the other bolts will I see those bolts pop later on in life... this could be something I will need to keep an eye on. Open for opinions here and again if anyone has used any of these tricks I'd like to hear about it.

When I swapped mine out, I noticed that if I didn't force the stud past the oil trapped in the hole, the stud would stop with the appearance the the stud was all the way in but it was compressing some oil that ran down the hole when the stock bolts were removed. I had to keep going with the Allan key and the oil would squeeze out until the studs were down all the way. I did mine with the head on using the one-by-one method.

I think the strength of the larger stud compared to the other 9 shouldn't be an issue as you will not be able to get close to the yield strength of either stud size. The only possible concern is enough material surrounding the new threads to hold the stud under torque load.

Are you going to try and do the repair with the head on? The mag press is a great idea but you need some substantial steel material for the magnet to bite but I am sure that you are on it.

The challenges never cease on these cars!

Oh and for the other nerds in here.. A time sert is made from Carbon steel http://www.timesert.com/html/12L14CarbonSteel.pdf with a yield strength of 78KPSI.

I don't fully know what VW uses for there cast iron but the best cast has a tensile strength of 62.5KPSI. http://www.anvilfire.com/article.php?bodyName=/FAQs/cast_iron.htm

That is a 12% increase over factory block limits. Mind you we also must consider there will still be steel to cast threading on the other side, but the diameter is larger so you may gain a slight advantage to going with these inserts.

If you opt for the oversize M14 x 2.0 bolt you should be able to hand-tap the hole.
You just pulled a 12mm bolt out of it, right? That is the drill size for M14 x 2.0.

And PB_NB, why wouldn't you blow the oil out of the hole before screwing in the stud?

Flee, I was thinking the very thing but at the time (poor planning on my part). I just ran the studs in with some perseverance. The oil appeared in some but not all of the holes.

A little vacuum with a tiny hose would have been great. I think a syringe could be used as well. I have yet to purchase a mighty vac which may also be a great option for this situation.

I think I shoved a thin rag on a 1/4" stick of something in there to mop it out.
My block was exposed for a while so there was some dirt in the holes, too.

Timeserts are good. Helicoils are good too. But just have to make sure you equal the amount of thread engagement. That's difficult to do with the head on. The head bolt holes are tapped deep to so the bolts/studs that have twice the tensile stress as the block don't rip the threads out of the block. Helicoils and time serts are usually about 1 diameter long, so you have to make sure you install enough of them to cover the distance of the entire originally threaded depth. Once you do, you will have a stronger joint than it was from the factory.
One advantage of helicoils is it's easier to fine tune the finished length. You just snip the excess. A time sert, you'd almost have to grind.

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I would not be afraid of helicoils or similar holding the load. This is a popular improvement for a weak block exactly like what happened to you. You get the load spread out over much more surface area than with the bolt itself.

Maybe if you left the head on, you could use the hole in the cylinder head as a guide for the drill bit (assuming it's big enough?). This would get you nice and square. Then run a couple Helicoil inserts down in the hole with some red loctite and install your head bolt with a light coating of oil on the threads and thread it in loosely to insure the inserts are lined up and everything is good. Once the loctite sets up, remove the head bolt and then re-install and torque to spec. It will be stronger than original.

Of course, if the clearance hole in the cylinder head is too small for the Helicoil tap, you'll want to pull the head off and use a mag base drill like you already suggested.

Good luck?

if you have a compact bench top drill press you could just bolt it to the block and drill through the base (already a hole there) into the block... of course you could just rent a mag drill

Same thing happened to Delvi years ago.... only other case of this happening that ive heard of.

I wanted to update fresh thread sert installed and currently running. the dang threads pulled flush out of the block with full bolt engagement... No idea why, but for those who are doing these just fyi you can fix it