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Discussion Starter #1
I think I might have cross-threaded a spark plug since the connector will not slip down around the plug, regardless of the connector, and regardless of whether I put in a new plug. I cannot actually see any out of plumb condition, but John at Motortorsports Garage suggested that was the likely problem. He couldn't fit me in to do the work, but suggested I try to clean/re-cut the threads.

That's great, but I've never re tapped anything unless held in a vise.

How difficult is this to do?

Exactly what size tap is necessary?

Any suggested techniques to ensure a plumb re tap?

Thanks in advance,

-Dan
 

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Go to auto parts store and buy a spark plug tap and some grease such as wheel bearing grease to use to capture metal shavings when using tap use 13/16" sparkplug socket to use tap. KD tool tap #730 example

See this picture of tap: http://www.sjdiscounttools.com/kdt730.html
 

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They make one now that you start from the bottom and go to the top of the thread. I've looked online and can't for the life of me remember which tool guy had it.(Snap On , Matco, etc...).

Try this. They should be able to get you just the one you need. It's idiot proof.(no offense)

https://www.mactools.com/portal/site/mactools/menuitem.6c9db894a3743751f735c110f070c3a0/?vgnextoid=6b0552850014d010VgnVCM100000426fa8c0RCRD&vgnextfmt=default

Paul
Isn't that one for if you have head off engine to go from combustion chamber side?

Or is this what you mean? http://www.costplustools.com/store/show_product/?product_id=41745
How does it work must have to retract it's size to get into plug hole and then expand it to fit threads?
 

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Here is the description of how it works.

Its patented design allows it to slip down inside the spark plug port past the damaged threads. Then it expands, engages the undamaged threads and begins chasing threads from the bottom up. All filings and debris come up out instead of falling inside the chamber. The Back-Tap™ will not let you cross the good threads up.
You don't have to remove the head..

Paul
 

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It looks like that bottom-up (or inside-out) tool is spring loaded. The cutting end can be expanded when the tube is retract up to let the spring expand.

Ok, the cheapskate in me say:
" I can pressurize the cylinder by hooking up the outlet of a vacuum cleaner to the intake tube. Turn the engine so the intake valve of that cylinder is open. Then I can blow all the metal shaving out when I use the cheap tool to recondition the thread :)!"
 

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The cheap tool is great if you want to remove the head when it strips the hole out.

Paul
 

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Discussion Starter #8
OK, thanks for the great links, guys. But I'm still unclear what size to use. Isn't the size one measured in metric rather than standard?

-Dan
 

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Discussion Starter #9
Eh, I guess I need to look at the suggested tools' descriptions first. Duh. Thanks a lot! I'll get to it.

-Dan
 

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Discussion Starter #10
Steve: How serious is the risk of screwing this up? Nobody I've spoken with has even suggested using anthing but the standard thread cutter (the cheap tool). All have adviced to use grease to capture the threads, and this is how I've seen it done on TV as well.

Am I correct to assume that if I "mangle" the threads I'm not much worse off than if I had brought it to the Alfa shop in the first place?

-Dan
 

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Are you able to get a strong light down in the plug well to see if it is really not straight? I would think it would have to be quite badly cross threaded to not allow the plug wire to slip over it and you should be able to see that. When you remove the plug, is there evidence of aluminum threads on the plug or in the well? I'm not convinced it is truly cross threaded if you say it looks plumb, maybe something else is not allowing the plug wire to snap over? Is the little threaded plug end (some have these, some don't) stuck in the wire end or something like that?
Charles
 
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Steve: How serious is the risk of screwing this up? Nobody I've spoken with has even suggested using anthing but the standard thread cutter (the cheap tool). All have adviced to use grease to capture the threads, and this is how I've seen it done on TV as well.

Am I correct to assume that if I "mangle" the threads I'm not much worse off than if I had brought it to the Alfa shop in the first place?

-Dan
Verify you really have a leaning plug and not an extra spark plug screw on tip inside spark plug wire terminal.

Always a chance of starting tap in a cross threaded manner, too but if plug is truly cross threaded and off center in hole then you need to try carefully to get taper started straight or you will just follow previously damaged threads.

If you having a leaning tower of Pisa looking plug that is one thing but is it fully seated in head or just part way in? Measure distance from tip of plug on a straight one and compare distances.

If you do screw up threads then you will need to have a thread insert or helicoil installed. That may make it neccessary to pull head to do it correctly due to metal shavings even with grease.
 
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