Cylinder head helicoils

[stonedrive]

Hi everyone, bit of a strange and worrying one. Whilst putting helicoils in cylinder head ready to fit manifold. I got to last one drill bit pretaped for depth, the last one being passenger side closest to front of car. I was carefully drilling when it just went through, but there was no resistance at all,had a look from other side doesn’t seem like a fresh break could it have been like this from previous rebuild. I’m now thinking nackered head. Cheers Steve

[Lingen]

Steve.
Unless I am misunderstanding you, how did you have a look "From the other side"? I feel sure a new head won't be necessary.
Mike.

[stonedrive]

Hi Mike, I turned head on it’s side and looked through the closest opening to where I was tapping inlet thread, looking from bottom of head through opening you can see where tap came through. Hope that makes sense, I should have taken photos really. Cheers Steve

[MandM]

Is it this hole steve

head 1.jpg

[stonedrive]

Hi Martin, that’s the one. I’m pretty sure it was already like that because when tapping there was no resistance at all, I had one tap to do where thread had gone that went ok, then thought to myself may as well do the rest when I discovered problem, why is it always the last one. Photos attached. Cheers Steve IMG_0558.jpg IMG_0557.jpg

[MandM]

If you cant get it repaired, I don't know who will do it maybe Randell engineering?, but I do have a solution that should work, before I left work I made some inserts from old head bolts, they are drilled and taped to 5/16 unc.

I use one on my head, I made some straight though ad some blind, have a look at these


IMG_20190220_132219.jpg

[flying farmer]

I have had this problem before, loads of silicone sealant on the thread and a flat washer under the bolt head does the trick.

If this was an pre-existing problem, that was probably done last time and you wouldn't have known about it because it worked.

[MandM]

Couldn't up load my word doc but snipped this

insert.jpg

mine was to large for a Helicoil , but was a dry hole, but I have blind ones

[MandM]

Neil solution will work , as you have the thread in there I didn't

[stonedrive]

Many thanks for suggestions to my problem everyone. Martin is the insert 5/16 or the bolt that screws into it. Cheers Steve

[Matt Cook]

The insert is made from a head stud, the internal thread is 5/16 UNC as per the original

[jbuckl]

This issue has occurred before I think.

if the break-through is to coolant, apply loctite sealant 574 or similar.