Tool Recommendation for Cross Threaded Spark Plugs

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billytuffnuts

billytuffnuts

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So somehow I managed to cross thread a spark plug on my #7 cylinder (I'm blaming the header clearance and not the user :p) and because it was one of the first threads that was damaged, I was unable to get a normal spark plug thread chaser to even bite.

I came across this tool: Powerbuilt 14mm Back Tap Thread Repair Tool - 640811 which I had no idea existed but boy did it save me a ton of work in trying to install a helicoil or timesert. It has an expansion tap that allows you to slide it through the spark plug hole and once you expand it, you simply chase the threads in reverse. It also helps prevent metal shavings from falling into the combustion chamber this way. For $25 it was definitely worth a try.

Anyways I just wanted to recommend this tool in case anyone else runs into a similar problem. It may not work in every situation but in mine it did. The amazon reviews are mostly good, I think the bad ones are probably due to user error more than anything.
 
billytuffnuts said:
So somehow I managed to cross thread a spark plug on my #7 cylinder (I'm blaming the header clearance and not the user :p) and because it was one of the first threads that was damaged, I was unable to get a normal spark plug thread chaser to even bite.

I came across this tool: Powerbuilt 14mm Back Tap Thread Repair Tool - 640811 which I had no idea existed but boy did it save me a ton of work in trying to install a helicoil or timesert. It has an expansion tap that allows you to slide it through the spark plug hole and once you expand it, you simply chase the threads in reverse. It also helps prevent metal shavings from falling into the combustion chamber this way. For $25 it was definitely worth a try.

Anyways I just wanted to recommend this tool in case anyone else runs into a similar problem. It may not work in every situation but in mine it did. The amazon reviews are mostly good, I think the bad ones are probably due to user error more than anything.
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Those Back taps work well. I sold them for years with many positive results. They start at the bottom where the threads are good and chase the threads as you unscrew it. Work it back and forth when you get to the bad spot.
 
I was going to say you shoulda pulled the head and tapped it from the chamber side. But then saw how that tool actually worked and it does the same damn thing. Genius. I’ve never seen those before.
 
TT5.9mag said:
I was going to say you shoulda pulled the head and tapped it from the chamber side. But then saw how that tool actually worked and it does the same damn thing. Genius. I’ve never seen those before.
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Yeah that was the last thing that I wanted to do. Only thing I had to do here was remove the header bolts and push it out of the way to give me some extra clearance to make sure the tool was aligned correctly
 
I've used a split die with great results. The last one was my steering shaft for the steering wheel nut. The split die goes around the good threads, it's locked together in the handle then you just spin it off across the bad area. Worked great! I didnt know they made the reverse for a threaded hole! very cool.
 
j_anderson said:
I've used a split die with great results. The last one was my steering shaft for the steering wheel nut. The split die goes around the good threads, it's locked together in the handle then you just spin it off across the bad area. Worked great! I didnt know they made the reverse for a threaded hole! very cool.
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I didn't know they made a split die. I guess we both learned something today!
 
billytuffnuts said:
So somehow I managed to cross thread a spark plug on my #7 cylinder (I'm blaming the header clearance and not the user :p) and because it was one of the first threads that was damaged, I was unable to get a normal spark plug thread chaser to even bite.

I came across this tool: Powerbuilt 14mm Back Tap Thread Repair Tool - 640811 which I had no idea existed but boy did it save me a ton of work in trying to install a helicoil or timesert. It has an expansion tap that allows you to slide it through the spark plug hole and once you expand it, you simply chase the threads in reverse. It also helps prevent metal shavings from falling into the combustion chamber this way. For $25 it was definitely worth a try.

Anyways I just wanted to recommend this tool in case anyone else runs into a similar problem. It may not work in every situation but in mine it did. The amazon reviews are mostly good, I think the bad ones are probably due to user error more than anything.
Click to expand...
Yes thread formers rock, they are actually used in high production machining as they have 10 times the life of a cutting tap. I’m not sure they would work in cast iron though, steel and aluminum they are great. Works best with thread forming lube oil formulated for thread forming specifically.
 
I like it. I would still put some grease on it to catch anything that still might fall back in.
 
ch1ll said:
Yes thread formers rock, they are actually used in high production machining as they have 10 times the life of a cutting tap. I’m not sure they would work in cast iron though, steel and aluminum they are great. Works best with thread forming lube oil formulated for thread forming specifically.
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I have the stock cast iron magnum heads but the damage was not too severe
 
Thanks for posting this. Looks like a good tool and fairly priced. I am not trying to hijack this thread, but I am going to post some pictures of a split die re-threader for lug studs I’ve had for many years that works well. Since J Anderson mentioned split dies in a previous post I figured it would be okay to throw this into the conversation. Tools like this can be a life-saver when you need them. Thanks again.

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