[AT] Stripped threads in alum head

Steve W. falcon at telenet.net
Mon Nov 30 15:40:32 PST 2009


charles bridges wrote:
>   I am working on an overhead cam engine and one of the bolts that holds the 
> cam shaft cap on is stripped.  It is an alum head, and I am trying to fix it 
> without pulling the head.  We are looking at 150 bucks worth of gaskets and 
> a lot of work to pull the heads.
> 
> The are two steel sleeves imbedded in the top of the head where the cam 
> shaft cap bolts go.  Looks like they are about a 1/4" down in the head and 
> protude about a 1/4" above, which lets them go about that far up in the 
> camshaft cap.  The drill bit or tap for the helicoil will not go through the 
> steel sleeve.  How do you get them out to drill and tap the hole out.
> 
> The camshaft caps take 8mm bolts and of course a 8mm tap will go through the 
> sleeve.  I need to drill the hole bigger in order to tap it for a helicoil.
> 
> 
> 
> Any suggestions will be appreciated.
> 
> Charles 
> 
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> 

Well you could pull the alignment dowel out BUT since those are usually
installed and then the bore is finished you could move it enough to mess
up the alignment.

As such I would probably run a GOOD 8mm bottoming tap into the hole.
Make sure you get good threads to the bottom of the current hole. Then
clean it out VERY VERY well. Now go find an 8MM hardened stud that will
thread all the way into the hole and leave enough for a nut and hardened
washer on top.

Coat the stud with Loctite Form-A-Thread.
Since you are installing the stud to stay you don't need to use the
release agent. The material will form a thread AND lock the stud in
place. This stuff can take 45 ft/pounds of torque on an 8mm size bolt.
That is assuming NO original threads.

I have used this stuff a few times to repair threads in various items
and other than one failure on my part when I didn't coat the bolt with
enough release agent and had to redo the repair, It has held up great.

Kit runs about 15 bucks.


-- 
Steve W.




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