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Stripped Threads in Exhaust Manifold Mounting Holes

Posted: Mon Apr 03, 2006 10:56 am
by MerrilGordon
Well I finally did it. Too many removals, replacements, and ham-fisted torqueings on my part. I stripped out the left rear hole for the exhaust manifold bolt. I’m still using stock cast iron exhaust manifolds so using those long bolts into the head.

I’m wondering if a longer bolt might find enough threads ?
Probably not a good thing to try.
I could drill out to the next size and use a larger bolt.
Don’t like having one different than all the others though.
Can the hole be drilled deeper without hitting a water jacket or something ?
Probably not a good idea either.
So there’s the Helicoil insert. Probably the best choice, but is there a better alternative ? Seems I remember reading about another type of insert recommended for Porsches that was stronger than a Helicoil. Any of you guys know about that one ?

Any recommendations welcome.
Thanks,
Merril

Posted: Mon Apr 03, 2006 11:05 am
by Barry
Merril,imo the helicoil is more than sufficient for the job.You could of course go for the solid insert thingy,but I reckon its overkill.

Posted: Mon Apr 03, 2006 3:42 pm
by matt
I'd be interested to see how the helicoil used, are they strong enough for the cam "cap" bolts. I noticed a hairline crack in my cam/tappet cover at the middle off the exhaust side cam and one of the bloody cam cap bolts has been stripped, well i can't get enough torque on it :twisted: I assume this led to slight movement, enough to crack the cam cover slightly :evil: before i pulled the motor......

anyway be interested to see how this is all done!

Posted: Mon Apr 03, 2006 4:14 pm
by Murray
Matt I used Helicoils on 3 of the 5 cylinder head bolts on an old 400cc Yamaha motorcycle I own.That was 10 years ago and they are holding up just fine.That was before I learnt about the importance of using a torque wrench when working with aluminium :lol:

Posted: Tue Apr 04, 2006 10:14 am
by MerrilGordon
Thanks for the input everyone. I'll go with the Helicoil.

Torque wrenches. Yea, I've got a big one but what's really needed is a small one for many of the fasteners into aluminum we have in our Alfas. I need to get one and not have any more screw-ups like this.

Merril

Posted: Fri Apr 07, 2006 4:13 pm
by x-rad
Helicoil...definately strong enough..much stronger than the alu...sometimes hard to find specific metric sizes...use thread assembly lube