Heli-Coil /// Sav-A-Thread /// Stripped Threads

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Johnny

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Just went through a frustrating adventure with stripped Spark Plug threads
in my 1979 Johnson 25.
THREE trips to NAPA to get a Thread Repair Insert to get the right one.

I would like to pass this little tidbit onto my fellow boaters.
GREAT item to keep in your tool box for less than $8.00 for two.

#1. Took cylinder head to a LAWNMOWER shop to get the Heli-Coil thing done.
He was out of inserts. I went to NAPA 3 blocks away to get the insert for him.
(HE called ahead to order the part).....
After I got it home, found it was too short - removed it with a Screw Backer Upper Thingy.
#2. Went BACK to NAPA for another thread insert. The Heli-Coil type with the individual
threads that just thread into the rethreaded spark plug hole......
I didn't like the way it fit into the threads so I took the cylinder head to NAPA for them
to look at it....... and ordered ANOTHER insert
#3. Next day .... went BACK to town, got the insert, put it on a spark plug and it was
a good fit. applied a few drops of HIGH TEMP THREAD LOCKER and the insert went right in and
locked into position quite nicely - very satisfied with overall results.

Edit: Yes, the "heat release point" is 450 to 500 degrees F. It says that on the product label.
so, if your cylinder head is that hot, I am quite sure you will see paint bubbling and turning gray and a
stinky burnt smell at that point. Which means you have far more problems than a loose thread insert
to address.
It is NOT recommended to put any kind of sealant on the Heli-Coil type that has the individual spiral threads
or you will essentially glue your spark plug into the hole !!

This is the item that people should have in their tool box !!! Well worth the advance planning.
I use L77JC4 Champion spark plugs. This item is a MEDIUM size. It comes in small, medium and large.
Heli-Coil.jpg


There is nothing more grand
than to be just simply messing
around in and old boat. POGO-1960
 
That's similar to what I use at work and works very well for a lot of applications. Great advice.
Edit - Our brand is Timesert , fixed 2 on a aluminum cylinder head yesterday (4/15) in a matter of minutes.
yty5y7y9.jpg
 
Don't want to rain on your parade, but if you carry spare spark plugs carry spare inserts also as most of the time they will come out when you pull the plug & are hard to get off the plug without ruining the threads on the OD of the insert.
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=348365#p348365 said:
Triple obsession » Yesterday, 21:30[/url]"]Don't want to rain on your parade, but if you carry spare spark plugs carry spare inserts also as most of the time they will come out when you pull the plug & are hard to get off the plug without ruining the threads on the OD of the insert.


I used a "save a thread" kit on a 25hp and the directions said to use a high temp RTV sealant and it did come out with the plug months later. But like Barefoot I then used a high temp stud strength loc-tite and it hasn't come out yet`
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=348394#p348394 said:
Charger25 » 12 Apr 2014, 09:29[/url]"]I used a "save a thread" kit on a 25hp and the directions said to use a high temp RTV sealant and it did come out with the plug months later. But like Barefoot I then used a high temp stud strength loc-tite and it hasn't come out yet`

Some folks do have good luck with them, but many don't. In the winter I work at a automotive machine/race engine shop & we use only heli-coil inserts. We've tried "save a thread" in the past and weren't impressed & we have had a few customers come in that had problems keeping them in.

Most high temp thread locking agents are only good for 500-650 degrees, once they reach that temp they break down & loose their bond. Heating & cooling cycles can affect them as a aluminum head & the steel insert have different expansion rates. If you have a exposed thread on the end of the plug & carbon gets built up on it the insert can get backed out when the plug is removed.

Keensert makes a good insert similar to the napa ones except they have vertical groves on the side with steel pins that stick up. Tap & install then use a special tool to drive the pins down into the threads locking everything together. Good, but a little pricey.
 

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