Broken stud leading to bigger problem

[yelcab1]

I am working on a non-Porsche aluminum block, broken head stud, drilled it out bit off center, now the bottom of the hole is slightly oval, and the drill for the helicoil does not make the hole round, with 20% of the hole outside of the circle so only 80% of the hole would be thread if I used a helicoil/timesert tap.

My options are:

1. tap it anyway and hope to hell it holds, (bad)
2. use loctite thread former, redrill, retap for helicoil or timesert
3. refill the hole with aluminum welding (don't know how or if it can be done)

Any other suggestions, pro/con from the aluminum case engine experts on the board?

PS: The hole is 4 inch deep, blind hole, bottom 1" part is the thread part.

[VincentVega]

I did a similar thing with one of the exhaust studs on the SC. I suggest getting a 'big cert' from timesert. The insert is oversized for this exact reason. The problem is still drilling straight though. Without a jog or a drill press it's going to be tough.

Good luck

[yelcab1]

Chris you are fast.

Big Sert does not come in 14mm x 1.5 pitch which is what I need

[beepbeep]

I found out that PO of my 930 did same sort of "DIY repair" and tried to drill out exhaust studs w/o real tools. Of course, he drilled off center (it's almost impossible to do this w/o real drill-stand).

In the end i had to precision re-drill this hole to 10mm (was 6mm), insert 10-mm helicoils and then make custom threaded 10-to-6mm studs.

That will do it.

[ruf-porsche]

Most welding shops can fill the hole with aluminum weld and most machine shops can drill and tap the hole for you. Hopefully the block is out of the car so taking it to the various shops is not a problem.

[TimT]

You could drill and tap the hole you have made ( to an acceptable oversize. then install a like threaded stud, cut it off flush, mark the slug you have installed, and drill and tap that.


oops... just read the hole is a blind and bottom threaded. that makes is really hard to fill with weld