99.9% sure I cross threaded a spark plug

[wastintime]

NGK in a 911... say it isn't so... in a 912, I'd be okay...

Yeah, I'd pull it out and look at it. As Bill said, maybe somone else cross threaded it at some point, but I promise you that you didn't with your fingertips.

[plymouthcolt]

Originally Posted by wastintime

NGK in a 911... say it isn't so... in a 912, I'd be okay...

Yeah, I'd pull it out and look at it. As Bill said, maybe somone else cross threaded it at some point, but I promise you that you didn't with your fingertips.

I can no longer find WR7DC anywhere locally.

[Jim Garfield]

I know that Hugh is being cautious and trying to save you from a major screw up, but as another opinion - I cross threaded a plug a couple of years ago and had good luck ( and maybe that's all it was) carefully chasing the threads and reinserting. If you were installing by hand I'll bet they aren't buggered too badly.

[plymouthcolt]

Well I ordered the Back-Tap tool and it should arrive this week. I will use it Saturday and post an update.

[the]

Originally Posted by wastintime

NGK in a 911... say it isn't so... in a 912, I'd be okay...

Why?

[Zeke]

Originally Posted by plymouthcolt

Well I ordered the Back-Tap tool and it should arrive this week. I will use it Saturday and post an update.

Good for you! I admire a man that has confidence.

[Nine9six]

Originally Posted by Hugh R

NO,NO,NO!!!!
Pull the engine and get a straight shot at it. My brother is a machinist at the Jet Propulsion Lab in Pasadena and I did the same thing and he said "Do you want to eff it up or do you want me to fix it". Don't just think you can ram a plug chasing tool into it! It takes a LOT of finess and expertise to not eff it up. Get a really, really experienced person to chase the threads. If you pull the engine take it to someone whose done this many times before. The difference is a $50-$100 shop charge vs. you effing it up and its a few thou. $$$ after you eff it up. Take that as gospel. I CAN'T EMPHASIS THIS ENOUGH, DON'T TRY AND DO THIS YOURSELF!!! IT SEEMS EASY, BUT YOU ONLY GET ONE SHOT AT NOT PULLING YOUR HEAD. THE FINESSE OF DOING THIS RIGHT IS WELL WORTH THE BUCKS TO SOMEONE WHO REALLY, REALLY KNOWS HOW TO DO THIS!!!!

I humbly disagree...spend the money and get the right tool as noted in the link to Grady's post. Dropping the motor would be one of the last resorts considering you have not applied any more torque other than with your fingertips and a 1/4 turn.
When using a tool as described in Grady's post, apply plenty of grease to the tools threads (cutting edges). This will catch any small bits of metal that may be removed with the tool.

I just ordered one from my local auto parts place. They
said they will match the $45 Amazon price, no shipping,
3.8% sales tax, should have it next week.

“KD Back-Tap 14mm Internal Spark Plug Rethread Tool.
Patented design allows for chasing spark plug threads
from inside the cylinder head and working outward.
This tool uses the better threads at the base of the
spark plug port and greatly reduces the chance of debris
falling into the cylinder. Works on 14mm spark plug
threads. Length of 6" allows for deep well plugs. Tool
can be used with 1/2" socket or wrench. Availability: In
stock Usually ships within 24 hours. Ships via UPS.”



They say it is 6" long.

Next week I’ll take some pictures using it on a disassembled
head and try it on a complete engine. One issue with a 911
is that it make the turn and fit down the sparkplug opening
and clear the chassis without removing the intake valve cover.

This looks like a tool that belongs in everyone’s tool box. I’m
going to see if it is suitable for regular sparkplug thread
maintenance. This has always been a difficult issue.
Perhaps it is somewhat solved.

Best,
Grady

[wastintime]

Originally Posted by the

Why?

I guess I'm being snobbish, I just think all 911s should run Bosch even the ones that came with Beru, but I ran NGKs in my 912, my WRX, etc... so it's not like I don't like the plugs, just don't think they suit 911s that well.

[plymouthcolt]

Ok here is the update I promised. I couldn't work on the car Saturday as I was in West Virginia most of the day. I got the Back-Tap tool and a mirror on a telescoping stick. I started working this morning.

I removed the valve cover and used the mirror to peer into the well. Boy was I surprised to see this...








What are those white fluffy things? Why they are Bounty paper towels (the quicker picker upper).



So I used my handy flexible claw to remove all traces of the paper. At this point I am elated--all this heartache caused by paper messing with the threads.

So I eagerly grab the plug, insert it in the plug socket, then start to turn and the same things happens again--two turns and then resistance.

At this point I know I will have to use the Back-Tap.






I lubricated the threads with grease and inserted into the chamber. The Back-Tap has a knob on top you turn clockwise to pull the draw bar and adjust the tapered thread to full 14mm.

Now this is easier said then done as the tool is just too short. I say it needs another two inches to make it a perfect tool. I could just BARELY turn the draw bar knob with the tips of my fingers. Compounding the problem is the the body of the tool wants to turn with the knob.

So I pushed down on the tool so it rested against the piston then I turned. The friction from the piston held the draw bar and let the knob turn. I then grabbed the tool and lightly tried to pull it out. The draw bar had not expanded enough so the threaded tip slipped easily past the threads the tool came out. I put it back in and turned the knob some more.

Again I tried to remove the tool and felt the thread finally engage. You have to be careful when turn trying to back tap as it's easy to turn the draw bar knob, thus releasing the draw bar and the tool slips out.

The instructions say you should use it 2-3 times expanding the diameter each time. I did it a total of four times. I did feel slight resistance but nothing I would classify as "torn up threads". I also did not see any metal particles in the grease. Regardless I did clean the tool and reapply new grease each time.

I grabbed the plug again and said, "here goes nothing". Lo and behold the plug went in like butter.

I started the car and she ran just fine.

So the tool is worth every penny of it's $50. The only con I have is that it just needs to be longer--about two inches.

Thank you every one here for your support.

[wastintime]

Congrats Howard, glad it worked out, and I knew the threads couldn't be too bad.

[m21sniper]

Originally Posted by plymouthcolt

While searching the internet I found this tool, http://toolmonger.com/2007/11/14/un-oops-that-cross-threaded-spark-plug-hole/. It supposedly can fix that cross-threaded hole from the inside — without pulling the head..

That's a pretty damned clever tool.

Sounds to me like you had miniscule amounts of debris or corrosion. You can tell just by looking at the plug that it's not cross-threaded. Personally, i would've just twisted a bit harder inserting it the first time.

[mjshira]

congrats and well done, you should be proud of yourself. a lot of people wouldn't have stuck it out. Not sure what those white things were, I thought maybe electrode at first.

[billybek]

Nice job, I am glad it worked out!!
Paper towel gave it enough of a push to start the plug down the wrong path?
Looks like an interesting tool.

[ajmarton]

Great post!

[RoninLB]

hell'ova wild adventure tale

[bhyde]

Ok, fess up, where did the paper towel come from?

[jkarolyi]

Neat tool...bookmarking this thread.

How the $)(@# did you get paper towels down in there?

[Gogar]

Nice!