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Spark plug thread repair

Posted:
Fri Nov 04, 2016 6:07 pm
by Tony Hart
I am rebuilding an engine and bought a new top end, not cheap. I put the plug in to do a leak-down test and it literally dropped in. There is about half a turn of thread at the bottom of the plug hole. This will have been about the third time I fitted a plug in the head. Don't think I had overtightened the plug. When I took the head off (again) there is no depth to the threads and no sign of stripped aluminium in the barrel. All by the by but my question is; can you reliably repair this thread with a kit without being forever paranoid about it failing?
The head is a unique design, (as far as I'm aware), and I don't fancy paying £100 for a new one if I can help it
Cheers
Tony
Re: Spark plug thread repair

Posted:
Fri Nov 04, 2016 6:48 pm
by MickYork
Plenty of repair kits on ebay with various lengths of inserts. Done correctly and loctited in I don't see a problem
Re: Spark plug thread repair

Posted:
Fri Nov 04, 2016 7:28 pm
by Warkton Tornado No.1
I bought a HeliCoil Sav-A-Thread M14 x 1.25 Spark Plug Repair Kit years ago ‘just in case’ when I saw one @ the right price (cheap!)
Eventually, it was needed & worked really well. I would totally recommend them & I have no doubt that the resultant repair is far stronger than the original.
Re: Spark plug thread repair

Posted:
Fri Nov 04, 2016 7:34 pm
by dickie
Warkton Tornado No.1 wrote:I bought a HeliCoil Sav-A-Thread M14 x 1.25 Spark Plug Repair Kit years ago ‘just in case’ when I saw one @ the right price (cheap!)
Eventually, it was needed & worked really well. I would totally recommend them & I have no doubt that the resultant repair is far stronger than the original.
Agree. I stripped a thread when replacing a plug in a ham-fisted manner on a p200e years ago. Nearby garage fitted a helicoil and it lasted years. Until a scrote stole it in 1986; maybe he's still using it. Rob, any news on my helicoil?
Re: Spark plug thread repair

Posted:
Fri Nov 04, 2016 7:59 pm
by Tony Hart
Many thanks all. Just ordered one so will see how I get on.
Tony