Stripped Spark Plug Threads

[JEBalles]

On a recently acquired, non-running, 1974 Honda CB360, I managed to strip the first few threads on the right cylinder's spark plug hole. What should I do? Do I need to replace the cylinder head?

[loepke72]

No, there is a Heli-Coil brand spark plug thread repair kit that installs a threaded sleeve into the existing spark plug hole, so you can repair the cylinder head. I've done this to several Ford V8s that blew plugs out of the heads and they seem to hold up fine. If you put lots of grease on the tap to catch machining chips, it can be repaired with the cylinder head on the engine. IIRC it's called "Sav-A-Thread".

[KarTek]

Time-sert also makes an excellent thread repair cylinder of sorts. I used one to repair the messed up glow plug hole on my E300 engine.

It's a little more expensive but how much is it worth to you to have a 'perfect' repair?

[kmaysob]

http://matcotools.com/Catalog/toolcatalog.jsp?cattype=T&cat=2166&page=2&#35276

scroll to the bottom of the page. its called a back tap

[Billybob]

An internal thread chaser will do the job with the least hassle, here's one:

http://www.pitstopusa.com/SearchResult.aspx?CategoryID=5020


I'm pretty sure Sears even sells a KD Tools model. You place it into the threaded hole, expand the tap by tightening the nut/bolt, the tap's threads engage the hole's threading below/past the damaged threads, then the expanded tap is backed up and out past the damaged threads.

Here's a thread mentioning a similar tool in post #8!

http://www.peachparts.com//shopforum/showthread.php?t=256614&highlight=spark+plug+thread

[JEBalles]

Originally Posted by Billybob

An internal thread chaser will do the job with the least hassle, here's one:

http://www.pitstopusa.com/SearchResult.aspx?CategoryID=5020


I'm pretty sure Sears even sells a KD Tools model. You place it into the threaded hole, expand the tap by tightening the nut/bolt, the tap's threads engage the hole's threading below/past the damaged threads, then the expanded tap is backed up and out past the damaged threads.

Here's a thread mentioning a similar tool in post #8!

http://www.peachparts.com//shopforum/showthread.php?t=256614&highlight=spark+plug+thread

And this does not require head removal, right? I should've said I cross threaded the first few threads, not stripped. My idea was to maybe remove the head and put in the spark plug backwards, but then I learned of these thread chasers. I was just going to use a regular one, but if I don't have to remove the head (which I'm trying to avoid) for this one, then I'll use it.

[kmaysob]

Originally Posted by JEBalles

And this does not require head removal, right? I should've said I cross threaded the first few threads, not stripped. My idea was to maybe remove the head and put in the spark plug backwards, but then I learned of these thread chasers. I was just going to use a regular one, but if I don't have to remove the head (which I'm trying to avoid) for this one, then I'll use it.

that is correct, you do not have to remove it. the tool in question will work just like your idea of putting the plug in from the back

[Billybob]

Originally Posted by JEBalles

And this does not require head removal, right?

As already mentioned by the previous poster you would not need to remove the head in your case. That fact as well as the fact that you don't need to drill, then tap for some other insert type fix is the advantage of trying to get things right with this type of tool as first resort. If you can straighten out the threads and get on with the project its worth the $50 in most cases. Using this tool is more a matter of finese that force, taking the time to make sure to get it seated correctly is always worth it. Taking the time to get the spark plug started straight is priceless! If you use a little oil to lube the plug threads and therebye allowing you to finger tighten it and "feel" it you will stand a better chance of avoiding another cross threading. Good luck!