Classic Alfa Forums

Had a thread go weak on the integrale head, a real problem with alloy pieces and steel bolts, the alloy is far softer than steel so eventually the threads can pull out especially if in an area of high stress like this repair, an engine mounting bracket. As it needs taking off every time the cambelt is changed it needs a good thread.

Now there is helicoil repairs but I'm not convinced about them as it's just a rolled piece of stainless threaded in, I've had these pull out of jobs with the bolt before where previous repairs have been done. I'm sure if it's just for a fit and forget repair then that would be fine, as long as the bolt wouldn't need to be taken out again.

So what else to do?

When the neighbouring one did this to me when the engine got rebuilt I drilled it out and tapped in a bigger hole and used a long stud so I could use a nut so as not to have to take it out of the alloy again. This isn't ideal as the bracket and spacer needed reaming out to suit the new stud size plus it makes it more awkward for fitting the bracket back on. Making two studs would double the difficulty.

I searched for an alternative and came across a system by Wurth called time-sert which matched my concerns over helicoil.

An expensive kit but thankfully I managed to borrow a kit, thanks again.

You start off by drilling out the damaged thread with the supplied bit.

Right hand side hole of this poorly taken picture!
Then the tool in the kit is used to cut a recess in the face, there's a stop in the tool so you know when it's deep enough, this is for the flange on the inset so it sits flush and doesn't go in too deep.
Next the supplied tap is used to cut the new thread for the insert.

The inset itself is steel and needs fitting with the insertion tool in the kit.
You'll notice it has a flange at the top that sits in the cut recess so it comes to a stop and doesn't wind in too far.
The insert goes in with the tool, winding down to the recces.
Now the great bit of design in this system is that the innermost thread of the insert is wider than the outer, so as you screw the insertion tool in it expands the insert to grip the hole fixing the insert in place so it can't wind itself out when the bolt is taken out in the future.
The recess allows the insert to sit flush..
So you end up with a permanent steel thread for your steel bolt so it will give years of good safe service.
It goes without saying that you have to take great care when drilling and tapping the hole to keep it square and straight, no point in having a wonky thread or you won't be able to line the bolt up, especially on a long throw like this!

That's a great fix and never seen before so nice to learn something. Thanks.

Not many people were Christened Adolf after Herr Worth!

Not many people were Christened Adolf after Herr Wurth!

A great fix Kev. A really nice installation.
They do some good stuff.

Ive heard of them but never seen one in action. I’ve got a pulled alternator bracket thread in an alloy block and looks like they would be a perfect fix for it.

I used a similar looking solid insert to repair a dead sparkplug thread once. The special tap used what was left of the original thread to pull itself in and cut the new. It was a cheap old car but I was depending on it for transport so didn’t even pull the head, just packed the tap with grease and cleaned it off after every couple of turns. Was fine for years and many thousands of miles after.

It is a great repair, head all back on and the bolt in question went in perfectly and never felt so secure.
More than sure it will do the alternator bot perfectly