fixing a stripped out alu hole

[metalmad]

So on my Saab, one of the injector clamp stud holes has stripped out (my fault didn't screw the stud in far enough)
Tried helicoiling it but she won't hold, don't think there's enough left for it to get a decent grip.
Its a diesel, so the compression is pretty darned high, when it stripped the threads, the only thing stopping the injector going through the garage roof was the injector hardline and it bent it, annealed it and it bent back ok, though I may yet replace it.

Picked up some of these inserts ( https://www.ebay.co.uk/itm/Slotted-...ae:m:m55h6y5LohUpp5jF5tZvEJQ&var=553131021248 ) in M8 (stud size)

However I'm not sure if there's enough meat in the wall for them.

Making it harder is that the threads are recessed down the bottom of a 1 1/2 deep hole, starting about 3/4" down.

If this don't work I'm looking at a replacement cylinder head (and tearing down the motor again)

Any suggestions?

 

[white91formula]

can you go to a larger thread ?

pictures would help....

 

[helterskelter]

Helicoil will be as good or better than the original threads if done correctly. You need to thread the helicoil to the full depth of the original thread. If you can't get a helicoil in there reliably I would attempt to keensert it. Again it's important to get the same engagement as the original thread.

Don't use the insert from ebay.

 

[joe49]

I've used this HTS 2000.

 

[metalmad]

Cheers guys,
Got it sorted out, re ran the helicoil tap down the hole, blew it out with compressed air, inserted the helicoil, tried a stud - snagged on something before the helicoil, ran an M8 tap down, cut the burr or whatever was stopping the stud threading in.
Used a high tensile 8.8 bolt of the same length as the stud was, snugged it down, started her up and no issues, even after holding her around 3750 rpm. (redline around 4500-5000 rpm)



Just now need to stick the arch liners back on (drilling out various sheared off fasteners along the way), new front tyres, and paint the vertical surface in front of the rear wheels that catches all the salt and other road grime (showing signs of surface rust so some anti corrosion primer and paint should protect her for a good while)

Then she's back on the road.

 

[gbynum]

Used a high tensile 8.8 bolt of the same length as the stud was, ...

Only issue is that 8.8 is not a high strength fastener ... likely should use 10.8 (or MAYBE 12.9) product to replace typical high strength heat treated stud.

 

[metalmad]

Only issue is that 8.8 is not a high strength fastener ... likely should use 10.8 (or MAYBE 12.9) product to replace typical high strength heat treated stud.

not even sure the stud was heat treated, GM don't list in the parts catalogue, doesn't seem that hard either...the aluminium would likely strip out before the bolt shears off, by a country mile...

IIRC 12.9 can be quite brittle, due to it being so hard...

Put it this way its a £700 / $900 car, just trying to get a few more years out of it.