# People Cross-Threading Spark Plug Hole Threads



## orangputeh (Nov 24, 2016)

I can't believe I ran across this again. 4th time in the last couple months. person tried to install spark plug and forced it in about half way and damaged the threads. First several times I cam across this was able to repair threads using that back chase tool someone mentioned her. Put chaser in with grease on it threads , expand threads , and then back tool out slowly . That cleans up and basically repairs threads so you can install spark plug.

This time no go. tried for an hour. Plug goes in easily about half way and then no go. The threads are too damaged. Had plenty of patience trying this because I believe the alternative is removing head and retapping and installing a heli coil.

There is another tool I think I can try to repair threads but I think I have to remove head so as not get filings in cylinder.

Very frustrating when people do this.


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## JLawrence08648 (Jan 15, 2017)

Close both valves, piston at TDC.

You can put a small piece of a thin rag soaked overnight in motor oil in the hole, rethread, pull the rag out. ???

Or rethread and use a vaccuum?

Or leave the exhaust valve open and blow out the filings???


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## Bondo 287 (Jan 31, 2019)

I'd do like @*JLawrence08648* says. Set to the compression stroke. 

If you can bore your thread with whatever works. 

This thing will clean up in there. They're strong magnets.


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## classiccat (Mar 1, 2014)

a ratchet/socket combo...

...for pulling the head 

:nerd:


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## JLawrence08648 (Jan 15, 2017)

Another thought, you could magnetize the tap? Put a rare earth magnet, they are really really super strong, on the top of the tap as you are tapping. The filings will be attracted to the tap.


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## crazzywolfie (Jun 2, 2014)

Bondo 287 said:


> I'd do like @*JLawrence08648* says. Set to the compression stroke.
> 
> Bore your thread with whatever works.
> 
> Then shove this thing down there.


if that is a magnet it really won't do you much good on aluminum:wink2:. 

if you are taking the head off couldn't you just retap the hole from the inside out? maybe even add some jbweld or 2 part epoxy to fix the damaged threads.


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## orangputeh (Nov 24, 2016)

crazzywolfie said:


> if that is a magnet it really won't do you much good on aluminum:wink2:.
> 
> if you are taking the head off couldn't you just retap the hole from the inside out? maybe even add some jbweld or 2 part epoxy to fix the damaged threads.


you're right , the head is aluminum . that is why i put grease on the back thread chaser threads to grab the filings. it just would not expand enough to repair all the threads. it repaired the top 1/3rd but not further in. the threads actually looked good but the plug would not go any further in after about a third to half in without binding. I know not to force.


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## crazzywolfie (Jun 2, 2014)

that is why i was thinking if you have to remove the head to fix things you can run the tap all the way through from the inside all the way out. that way all the threads would line up and work but definitely a lot more work if you have to remove the head.


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## Bondo 287 (Jan 31, 2019)

crazzywolfie said:


> if that is a magnet it really won't do you much good on aluminum:wink2:.
> 
> ... .














LOL Oh man, I got schooled. :thumbsup:


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## Lottstodo (Feb 16, 2018)

What I do when I can, is take an old plug and with my grinder with a cut off disc is cut 4 lines at each 1/4 through the threads to create a self tap with the plug. Make sure you dont leave burs in the plug threads with you grinder , if so just clean them up quick before using. I find it removes less material than a tap, and has saved many plug threads. 

I also use a old hand held air sandblaster gun assembly with a length of 1/4" rubber hose attached to vacuum or siphon debris from cylinder.

I also tell everyone that I use a 4-5" length of 1/2" rubber hose to install a spark plug. You can spin it right in to where the washer is touching, then use your socket to tighten. and its really easy to tell if it wants to cross before any damage is done, unlike the torque that you really cant feel if you use your socket and ratchet to start a plug


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## orangputeh (Nov 24, 2016)

Lottstodo said:


> What I do when I can, is take an old plug and with my grinder with a cut off disc is cut 4 lines at each 1/4 through the threads to create a self tap with the plug. Make sure you dont leave burs in the plug threads with you grinder , if so just clean them up quick before using. I find it removes less material than a tap, and has saved many plug threads.
> 
> I also use a old hand held air sandblaster gun assembly with a length of 1/4" rubber hose attached to vacuum or siphon debris from cylinder.
> 
> I also tell everyone that I use a 4-5" length of 1/2" rubber hose to install a spark plug. You can spin it right in to where the washer is touching, then use your socket to tighten. and its really easy to tell if it wants to cross before any damage is done, unlike the torque that you really cant feel if you use your socket and ratchet to start a plug


how is that different than maybe the Lisle 20200 Thread chaser on Amazon?

can you post a picture of your plug thread cleaner?


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## Lottstodo (Feb 16, 2018)

Cant post picture , but the difference is that I already have the old plugs and the grinder so I can make it with any plug and thread that I want to and not have to keep buying thread chasers.


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## SnoThro (Feb 20, 2016)

You grease the tap to catch most of the thread chips and then use compressed air to blow the rest out. Its done every day on engines far more expensive than snow blowers.


If you don't have a kit and don't want to invest a lot of money get the Heli-coil save a thread kit. 5334-14. Works really well.


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## drmerdp (Feb 9, 2014)

Lottstodo said:


> Cant post picture , but the difference is that I already have the old plugs and the grinder so I can make it with any plug and thread that I want to and not have to keep buying thread chasers.


Clever idea making a chaser out of spark plug. Not quite as ideal as a real chaser but super thrifty. 

Seems like we have an epidemic of people starting their plugs with a socket. I always start plugs by hand, cheap insurance. 

I too fixed a Honda with a cross threaded plug, but a greased up reverse chaser did the trick.


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## Sid (Jan 31, 2014)

All of the above. I always started plugs by hand. Power tools are dangerous in some hands, but it does create business.
Sid


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## RedOctobyr (Mar 2, 2014)

Geez, I'm far too chicken to start a spark plug with a ratchet, much less power tools  Good suggestion with the rubber tube, as long as the tube is straight. If it has any curl to it, it might make things tougher, since it would be trying to tilt the plug to the side. You'd still feel the resistance, but you might have better luck actually getting it in straight by just using your fingers. 

I've heard that suggestion for other fasteners too: For an impromptu thread chaser, cut grooves lengthwise along a bolt. The grooves give the metal chips a place to go (like on a tap), vs getting jammed up in the threads. I haven't tried this myself, but I keep it in mind in case I'm suddenly in a bind.


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## gregg (Nov 23, 2012)

I start plugs by hand buck use the 1/4" hose to start the plugs in my Ford Ranger.


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## AKAMick (Jan 24, 2019)

I would not worry to much about tiny particles of aluminum getting into the combustion chamber as aluminum shavings can be ignited and burnt, people don't think aluminum burns. It burns ferociously as the Royal Navy found out during the Falklands war when the aluminum armored destroyer HMS Sheffield was hit by an Argentinian anti-ship missile, it burnt to the water line and later sunk with a great loss of life. After the war all the aluminum armored Destroyers in the Royal Navy where all refitted with Steel armor. Combustion chamber temperatures will incinerate tiny pieces of aluminum and expel it out of the exhaust. Try not to get it in but don,t lose sleep over tiny pieces not being retrieved from the spark plug hole when rethreading or helicoiling the head.


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## JLawrence08648 (Jan 15, 2017)

A few aluminum filings which aluminum is very soft are going to score a cast iron cylinder wall? Or even an aluminum wall, as the piston comes up, it's going to get blown out the exhaust and I agree with AJAmick going to get incinerated.


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## tabora (Mar 1, 2017)

I've heli-coiled (or other types of threaded inserts) in aluminum heads (mostly old outboards) a number of times. I have never had to remove the head. Just rotate the crank until your valves/ports are closed, and then have at it. Once the new thread is in place, stick a compressed air blower tip into the plug hole and blast out the bits. The ones I have were about $6.50 at Home Depot.


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## captainrob1 (Dec 16, 2018)

The tool is called a “Backtap”. There are different sizes. So check that first so you get the right size. I have two and used one on my Honda Pressure Washer. It worked. If I encountered resistance as I backed the tap out I went down and restarted it. The grease grabs the filings. I found out about them on YouTube. The counter guy at NAPA was unaware of it and I showed him the part number. I removed the air cleaner to allow more working room with the wrench.


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## captainrob1 (Dec 16, 2018)

Here are photos of the Backtaps


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## captainrob1 (Dec 16, 2018)

Sorry, not sure if the first set came thru - horrible pop ups causing numerous re signing in.


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## sturgissteele (Feb 7, 2019)

captainrob1 said:


> Sorry, not sure if the first set came thru - horrible pop ups causing numerous re signing in.


Whoa! Expensive little buggers! $172 @ Napa. Good to have on hand when dealing with this sort of problem, though.









Sent from my moto x4 using Tapatalk


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## dbert (Aug 25, 2013)

Too much of a hack to really recommend, but I've seen it done....
With piston at bottom just prior to compression stroke...Fill the entire cylinder with shaving cream. After tapping new threads slowly rotate crank. The filings are pushed out to plug opening entrained in the foam of the shaving cream


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## RedOctobyr (Mar 2, 2014)

I just saved you $130, they're $36 here. Fortunately for you, I only charge a 10% finders fee!  



https://www.amazon.com/KD-3691-Back-Tap-Spark-Rethread/dp/B00T3M69P6/ref=sr_1_3?ie=UTF8&qid=1549829742&sr=8-3&keywords=spark+plug+back-tap


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## RedOctobyr (Mar 2, 2014)

dbert said:


> Too much of a hack to really recommend, but I've seen it done....
> With piston at bottom just prior to compression stroke...Fill the entire cylinder with shaving cream. After tapping new threads slowly rotate crank. The filings are pushed out to plug opening entrained in the foam of the shaving cream


That's a slick idea, thanks! I'll have to remember that if I ever run into this. 

Plus it would leave the cylinder walls nice and hydrated, with a close, smooth fit to the piston rings.


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## DARAL (Dec 28, 2020)

orangputeh said:


> I can't believe I ran across this again. 4th time in the last couple months. person tried to install spark plug and forced it in about half way and damaged the threads. First several times I cam across this was able to repair threads using that back chase tool someone mentioned her. Put chaser in with grease on it threads , expand threads , and then back tool out slowly . That cleans up and basically repairs threads so you can install spark plug.
> 
> This time no go. tried for an hour. Plug goes in easily about half way and then no go. The threads are too damaged. Had plenty of patience trying this because I believe the alternative is removing head and retapping and installing a heli coil.
> 
> ...


Maybe factory workers need to take more care in threading the head Mine was way to tight taking it out. I’m more than p______ off at this! I have never cross threaded a spark plug in working on engines for 55 years until now Angle of plug to side of engine is also a stupid design


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## LouC (Dec 5, 2016)

Reading some of these threads I wonder if its also an issue with the quality of the aluminum or the machining of the threads. I've had a number of Briggs 4 stroke engines, 3 Echos, 1 Husquvarna, the one Toro/Suzuki, one small Suzuki outboard, all with aluminum heads, none of them has given me fits trying to change a spark plug. Also, it is possible for on some engines for a few threads of the plug to protrude into the combustion chamber, these can then get coated in carbon which can damage threads when you remove the plug. 
The back taps look interesting. Kind of like a backwards thread chaser.


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## farmer52 (Dec 27, 2020)

If the head is aluminum, the engine should be cold before removing the spark plug.


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## 140278 (Aug 27, 2020)

DARAL said:


> Maybe factory workers need to take more care in threading the head Mine was way to tight taking it out. I’m more than p______ off at this! I have never cross threaded a spark plug in working on engines for 55 years until now Angle of plug to side of engine is also a stupid design


i have to disagree with stupid
one single cylinder and twin ope cross flow port engines there is only so much room to place the valves in the chamber which is in most cases a hemi or semi hemi. the plug needs to be as close to center as possible which means at a angle to help achieve the correct fire within for the required pollution specs needed by the epa and Ca carb 
use of proper tools to remove the plugs is a most, either a long ohc 4 valve socket or a flex socket with a 6 inch extension along with a long spark plug ratchet never fails .we are no longer seeing torque we are seeing partial turns like torque to yield so those tiny tools found in the box stores never work right, 
we are also seeing cheap made in china spark plugs that have cheap steel causing problems with seized plugs 

on a lct engine the manual reads 
quote, 
4. Install the spark plug carefully to avoid cross threading. Screw in spark plug by hand until it stops turning.
5. Tighten the spark plug with a 13/16-inch (21mm) spark plug wrench. Tighten 1/4 turn after the spark plug seats. end quote 
on a loncin used by toro
quote
6) Install the spark plug and use a spark plug wrench
to tighten it into the cylinder head.
7) When installing the spark plug, in order to prevent
cross-threading, first use hand to screw it in the
direction as shown by the arrow to install it into the tapped hole in the cylinder head, then
tighten with a plug wrench to compress the sealing washer.
8) If installing a new spark plug, tighten 1/2 turn after the
spark plug seats.
9) If reinstalling the used spark plug, tighten 1/8-1/4
turn after the spark plug seats. end quote


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## 140278 (Aug 27, 2020)

farmer52 said:


> If the head is aluminum, the engine should be cold before removing the spark plug.


and the plug going back in should be lightly coated with never seize ,


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