Stripped Spark Plug Hole

[aj81spider]

My newly rebuilt engine came back without any spark plugs. Last night I was putting them in and the #3 plug is stripped.

After a little research it appears I will have to rethread and put in an insert. I'm looking for thoughts and opinions on whether I have to remove the head to do that (and any other tips on what to be careful about).

On the plus side the engine is out of the car so working on it is very easy right now. On the minus side everything is brand new, so pulling the head means new gasket, new timing belt, etc when the ones on it have never been used.

[RRoller123]

I too have a slightly bunged up #2 plug thread and when I discussed this with a couple of local mechanics, they indicated that they would do it (helicoil) with the head in, since the small amount of aluminum shavings would pass easily past the exhaust valve, and the Al on steel wouldn't cause much trouble. I suggested that I would get a piece of ~1/2" clear flexible tubing and attach it to the shop vac and probably could get the majority of the Al shavings out anyway. Haven't done it because the plug in there is new and it will be a looong time until I have to pull it, but this was how the conversation went fwiw.

Pete

[aj81spider]

Thanks - and I like the tubing idea!

[majicwrench]

You can certainly do a helicoil without pulling head. I would rather not see all that AL shavings in cylinder tho, a shame on a new engine.. If you choose to pull head,no need to change belt, or for that matter, head gasket since it aint been run. Or heck, a head gasket is cheap.
Heck, you could do the helicoil with head on, but turn engine UPSIDE DOWN while doing it, then blow, vacuum, rinse etc.
Keith

[azruss]

I would stuff the sparkplug hole with papertowels. this will catch the shavings before they can work their way down the cylinder wall. they will be easy to suck out along with the paper towels. Does remind me of the first semi tractor i painted. stuffed the input with newspaper and forgot to take it out. imagine my surprise when the exhaust pipe coughed up chunks of edge-singled newspaper.

[ORFORD2004]

Put a lot of grease on the tap of the helicoil. The grease will catch the shaving.

[RRoller123]

Do it with that piston at TDC too.

[aj81spider]

Thanks - those are all good suggestions.

I'm on vacation the back half of the week and will tackle it then - using several of the suggestions above.

[aj81spider]

I successfully completed the installation of the insert. The engine is not in the car, so I won't know how it runs for a long time. However I figured I'd share what I did for anyone in a similar situation.

I started with a helicoil kit purchased from Amazon. It has the tap, an expander tool and three sizes of inserts. I used the longest of the inserts.



I looked at doing the tapping with the engine on a stand, upside down as I thought that was a great idea for keeping the shavings out of the cylinder. However this is my first helicoil and first tapping and I was not confident about my ability to do it upside down, so I ended up doing it with the engine upright.

Per the suggestion above I loaded the tap with wheel bearing grease. This worked great. The shavings were caught in the grease. I turned the tap one rotation then backed it out, cleaned the grease with shavings, put more grease on and did another rotation. This was somewhat time consuming and tedious, but it appears to have captured virtually all the shavings.





After the tapping was done I used RRoller's suggestion and connected a flexible plastic tube to my shop vac to pull out any stray shavings. I didn't see any in the cylinder (although I still vacuumed it out), but there were a few stuck to the walls of the hole that I pulled out with the hose/vacuum. Here's my sophisticated vacuuming setup:



The directions for the kit said to put high temperature RTV on the threads of the insert. The highest temperature RTV at the auto parts store was Permatex Copper, so I used that. The auto parts guy did not fill me with confidence when he said that was the right stuff, but there was nothing else, so I hope it's right. The insert threaded in nicely. I used the sparkplug to get it the last bit in. One tip - use an old spark plug, not your new one - the RTV got on the plug and I spent some time cleaning it off. I used the expander to lock the insert in and it's been sitting overnight to let the RTV cure. Here's the finished insert.



End to end the whole project took about an hour and a half, including clean up.

[narfire]

Thanks for the write up and pics AJ.
Looks like you nailed it. I hope this can sit in some far recess of that grey matter between my ears and bring it forward if needed. I like the grease tip, good idea.
Chris

[RRoller123]

That sounds great! Glad it went smoothly. Things like this can be nerve wracking.