Spark Plug Repair

[Jeff Ninebar]

Going to need to helicoil a spark plug thread, what size to I need?

[Jeff Ninebar]

any takers?

Just need to know what the thread size is on a normal spark plug. ta!

[LiamR]

Apologies but I have no idea....although I did mine years ago!

Am sure someone will pipe up in a bit with the answer though :agree:

If not, ask the wizard!;)

[R5MJH]

does this help jeff

http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf

look under b8eg:agree:

looks like a 14mm diameter mate

cheap as

http://www.ebay.co.uk/itm/14mm-SPARK-PLUG-CYLINDER-HEAD-RETHREAD-KIT-TAP-REAMER-HELICOIL-THREAD-INSERT-/251354311294?pt=UK_Hand_Tools_Equipment&hash=item3a85e26a7e#ht_1059wt_904

[gtmatt]

I used a spark plug thread chaser , worked a treat,depends on the damage , I just crossed threaded mine.

http://www.machinemart.co.uk/shop/product/details/cht261-spark-plug-thread-chaser?da=1&TC=SRC-spark%20plug

[Bigfoot]

Just remember to do this with the head off else will get a lot of crap into the block or there are tools, not sure where from, which you can put in the hole and then it spreads out to then cut it back up lifting all swarf with it.

[Jeff Ninebar]

thanks for the help guys. The thread is shot to bits, the crests are falling off so will need to tap and put in an insert. head is off as well so can keep clean

[ScottKinnear]

I know you say your threads are shot. But I have one where you put it in. Then expand it and re thread from the back/ forward. Well not re thread just follow the good ones and re cut the bad ones. You can lend it if you want? Bring it to the surrey meet ?

Weathers bad so I don't think I'll be attending :(

[michael tierney]

something like this http://www.ebay.ie/itm/14mm-SPARK-PLUG-Thread-Repair-M14x1-25-Solid-Insert-/190260704291?pt=UK_Measuring_Tools_Levels&hash=item2c4c6bf423#ht_362wt_972

[Jeff Ninebar]

So to follow up on this:

I got a cheap thread repair kit hoping it would do the job. It didn't. The tap didn't have a tapered head to drill out the hole and re-thread to fit the inserts. Imo its just a tap with some inserts. You'd have to find the right size drill bit to bore out the plug hole and then thread it with the tap.
This is the cheapy tap, do not buy it!
http://www.ebay.co.uk/itm/390702180617?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649


So I did some research and went for a V Coil tap/reamer and inserts. Works a treat. The tap bores out the hole then threads it. Takes a bit of time to bore out the hole and its not till the top section that the threat starts to cut, I was worried at first that it was just going to cut a massive spark plug hole and not thread it!
This is the kit:
http://www.ebay.co.uk/itm/160581469465?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

It works so well and the new thread is so good, I'm considering doing the other 3 plugs as the thread on them is a bit rough. I did this with the head off, and I would not recommend doing this with the head on as a load of metal comes out the bottom of the hole.