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Stripped thread Inlet manifold - pls Help

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So today, while replacing all my vacuum hoses to try and fix an issue with lack of power and occasional engine labouring (to the point of almost stalling a couple of times), I found the thread of the cylinder head that this bolt in the inlet manifold goes into was stripped (see pics). The bolt itself is fine.


Am working away from my usual workshop, so didn't do up with a torque wrench, just went by feel - big mistake..


I've put it all back together, thankfully the engine does run. I was able to get a tiny bit of grip on the bolt in question, but it definitely needs something to be done long-term. Question is - what method should I use?


I have replaced threads using Helicoil before. It does work but is a faff. 


I have also repaired by drilling out slightly and tapping a larger bolt thread - that usually works really well.


Because I'm away from my usual workshop, I didn't have my thread gauges. Can anyone advise the thread size on that bolt? 


Would really appreciate any advice on which method to use or a third method?


Many thanks,







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A helicoil or thread insert is the correct & proper way to fix this, they are way stronger than tapped

threads into alloy anyway.

We do this at work all the time with new components if they are to be continually removed.

The thread / inlet bolt in question looks to be M6, but could be M8. 

Can you not measure it, or screw on a nut to confirm? You don't need to use vernier calipers a rule will do

you'll soon tell if there M6 or M8 obviously 6mm dia or 8mm dia.

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