Damaged plug thread!

[G-NIPR]

Hi Guys,
Was doing a 'service' on NIPR yesterday, and found all of the plugs harder to remove than normal.
I have left it longer than usual due to protracted down time this year, and they were tight.
All bar one came out ok, but number seven of the eight proved tricky. It seemed to come out ok, but upon fitting the new plug the thread appeared to have been damaged. Not cross threaded, but damaged upon removal of the old plug. It wont really bite on the new plug (I have tried two), and only goes in a couple of threads and feels loose.
I really want to avoid removing the head if I can, and wondered if the 'timesert' system of thread fixing is ok for us to use.
I have been told to avoid helicoils as they are prone to blowing out.
Any advice would be welcome. Neil?
Thanks.

Paul.
G-NIPR.

[Neil Spooner]

Hi Paul,
Sorry to hear the Nipper is unwell.
Firstly avoid using copper based thread lubricant (I don't know if you did, but the copper will react with the steel/alloy and weld the plugs in, use a graphite lubricant, such as Graphogen)
I have had very little long term success with thread inserts of any kind, but would suggest the helicoil is still the best. It can be done without removing the head:
1-Remove both plugs on the affected cyl'.
2-To help prevent swarf entering the cyl' fit a cylinder leakage adaptor to the other plug (if you don't have one, you can make one from a spare plug, drill out the center, make sure all the loose ceramic has been cleared from the plug inner end, fit a hose to the outer insulator) and apply compressed air to the cyl' whilst using the tap. The pressure doesn't have to be high, it is just to blow out any swarf as it is created.
3-Apply grease to the tap to help the swarf stick to it.
4-Use the helicoil tap as straight as you can. Utilise the plug in the other cyl' on the same head to help establish alignment.
5-Clean the grease from the tapped out thread so it is dry, and fit the insert without lub'.
6-Much of the heat in the plug is lost through the thread, so once helicoiled the plug on that thread will run hotter, I would recommend using a plug 2 grades cooler and see how it runs, one grade may be enough, but having had a plug fail due to over heating is not fun.

Spark Plug (2)1 2.jpg (48.83 KiB) Viewed 8207 times

Spark Plug1 2.jpg (54.46 KiB) Viewed 8205 times

I don't like Champion plugs, and would always recommend NGK.

Good luck!!

Neil

[G-NIPR]

Thanks as always, Neil.
Bugger, I have been using copper lube for my plugs all the time. Won't anymore.
I will look at my options and sort it one way or the other..
Will report back soon,

Paul.
G-NIPR.

[Neil Spooner]

I will post a new topic on the 'site regarding the use of Copper lube's.
If you do decide you want a permanent repair send the head to me and I will get it welded and rethreaded, I have spare heads, but if you decided to go that way I will need the old head anyway to measure chamber volume to match your other one.
Neil

[Pat Blenkinsopp]

Neil...your a bit of an engineer on the side a'rnt you.
Sound advice as I fell foul to this one couple of years ago.
I would't however recommend Helicoils. There is a much better
but similar system (cant remember the name) which consists of a solid
threaded insert, Threads on inside and outside, but not like the spring like
Helicoil. These work very well and are easy to put in. They are
however expensive, but our lives could depend on them!
I have virtually given up flying due to long term sinus problems...
serious pain in the descent phase. I hope to get it fixed but am sixty
and have ticked virtually every flying box so no regrets.
ASXI is still for sale if you hear of anyone who might be interested
(permit until Oct 2013, and running as sweet as anything)

Anyway keep the faith... and that good advice coming.
Happy new year to you and the family, and indeed all you Nipper fan
out there.
Regards, Pat

[Neil Spooner]

Hi Pat,

Sorry to hear you are suffering, and also sad to see you are leaving the Nipper frat'.......good luck with whatever you do.

The other inserts I have used, "timeserts" is one name, Bluepoint (snapon) also do them....the problem with these is that if they come out you create problems fitting new ones.....helicoils are easy to refit using a new thread insert.....just my opinion!!

Hippo New Year!

Neil