Failed Spark Plug Thread Repair

[97gsxIA]

Ok so as the title states, I had a spark plug strip out (took plugs out and tightened them way too many times apparently).

I used a spark plug repair kit, retapped the hole and placed the insert in with red loctite. I used the taller insert available which i believe is the correct one. The very top (seat) of the insert broke a little as a tightened it in ( Much swearing ensued and this is what I think is my problem.) Low and behold, 60psi compression in that cylinder and motor runs like shit at 10in/Hg Vac... I doubt I nicked a valve in this process, but what are the chances?

The tap was straight and besides being tough on the hands, wasn't that difficult to perform.

So, I need to pull the head and take this insert out and retry with a different one. Problem being red loctite on the threads.

You think some JB weld on the threads of a plug, insert it... let it cure.. and pull it out would work? I am not a fan of trying to tap an even larger hole.

Let me know what you think.

 

[NordicSaab]

There are many ways you could do this but these would be my 2 thoughts...

1) weld over threads in cylinder head and re drill/tap the spark plug holes

2) Time Sert thread repair kit. If you are not familiar they are like a helicoil on steroids. Main problem is a kit will be well over $100 for what you're doing. Main benefit is the "repair" will be stronger than oem

 

[97gsxIA]

There are many ways you could do this but these would be my 2 thoughts...

1) weld over threads in cylinder head and re drill/tap the spark plug holes

2) Time Sert thread repair kit. If you are not familiar they are like a helicoil on steroids. Main problem is a kit will be well over $100 for what you're doing. Main benefit is the "repair" will be stronger than oem

#1 I have never heard of anything like this before. You want to weld the inch tall aluminum thread well completely shut then drill my own spark plug hole and tap it? Problem here is theres a steel insert in the hole already.
I'd like some other input on that option first.

#2 is what was performed on it initially, and the idea of tapping an even larger hole for an even larger insert on a hole that has an insert stuck in it seems troublesome.


Anyone else have suggestions?

 

[NordicSaab]

You don't really have many good options...

If your looking for a sure fire fix: Replace the head.

BTW: JB weld is not the answer

 

[97gsxIA]

You don't really have many good options...

If your looking for a sure fire fix: Replace the head.

BTW: JB weld is not the answer

Yes, replacing the head is viable.. but why not exhaust all options before replacing the whole head? That's just a waste of money.

I'm not JB welding anything into place, and I'm quite aware of JB weld not being the answer for just about everything. It would be JB welding a plug into the insert to overcome the red-loctite's breaking point between the insert and newly tapped hole so that the insert AND plug spins out. This isn't my first rodeo.

 

[NordicSaab]

Well I think the first suggestion of welding and drilling is really the right way to do this. Use a torch to heat up the insert and remove it. Weld in additional aluminum material. And re drill and tap the head.

that would be my suggestion. Good luck with whatever you do

 

[serviceguy]

If you're planning to take the head off anyway you can just try to use a thread repair tool threaded from the combustion chamber side of the head to try and remove the insert. Red Loctite should be heated in order to be removed as mentioned in a previous post.

 

[97gsxIA]

I'v also been told a spiral point screw extractor and some heat would get it out, I'm worried about fudging the threads tapping the extractor in, though, but that could be the least of my problems. Looks like I'll start there, then move to taking the head off to implement more "aggressive" repair options.

I'll keep this thread up to date, let me know if anyone else has an idea to pitch in the pot.

I know the spark plug seals at the seat and not the threads, anyone have advice on assuring a good seal after a new insert is installed?


Thanks for the attention fellas.

 

[serviceguy]

Whatever you use make sure the electrical conductivity is good enough for the spark to happen.

 

[boosted-tsi]

Take it to a machine shop before its beyond repair.

 

[luv2rallye]

^+1

 

[JacksonAuto]

There are a few correct ways to repair spark plug threads. A heli-coil, JB weld and other on-car repairs are great for shade tree mechanics but aren't considered to be reliable repairs.

All acceptable repair methods require the removal of the cylinder head.

Depending on the extent of the damage, a Time Sert may work. This is a heavy duty, steel thread insert. When we install these we put the head on a vertical mill so we can precisely locate the repair. It can be done by hand but it's easy to install the insert crooked.

If material has been removed by previous repair attempts it may be necessary to weld the hole shut and re-machine the threads. This is an extreme case but it can be done.

 

[97gsxIA]

I've spoken to my machinist. The goal of the thread was for advice on best methods to extracting the insert so that there is a GREATER chance at repairing the threads. Not asking who I should take my head to because I am incompetent.

What exactly do you think a machine shop would do other than extract the insert and re-tap (or fill and tap) it if damaged?

If I gave up on everything I did and handed off to my machinist, he'd be a rich man, and I'd be a broke POS with little to no know-how. I have 2 heads sitting on the shelf, if I wasn't set on doing this in my own shop, I'd just take it off and build off another core.

So please, I would appreciate some more constructive opinions other than belittling my situation by telling me to take it to a shop before I %$!& it up.


Thanks Jackson. The insert is a Time-sert (as using helicoils would be a mistake as coil-type inserts do not work on spark plug threads), and again, the JB weld idea was not to repair anything, but to extract the insert via overcoming the red-loctite's strength threshold. A vertical mill and machine shop will be on the docket as soon as I exhaust all of my means. Do you have an opinion on extracting the insert whether the head is off.. or on the car. Either way, it's going to be fixed by myself either in my shop, or at my machinist's.

 

[boosted-tsi]

you should be able to pry the very top end of the first coil of thread insert out of the hole and grab it. with pliers or somethimg and twist counter clockwise and pull. should come right out

 

[boosted-tsi]

I wasn't trying to be belittling just thought if you needed to post a thread to ask you may want help from youre machine shop. hate to see it get to bad and not be fixable

 

[ervin00]

How about a easy-out (bolt extractor) with a extension, maybe heat the insert so it comes out easier lots of people has decent luck with using them me included.
Although the risk of something falling down in your cylinder and ruining the engine has to be considered, so I think most people would just remove the head in fear of just that.

 

[ervin00]

Sorry did not see you already mentioned the easy-out

 

[NordicSaab]

There are a few correct ways to repair spark plug threads. A heli-coil, JB weld and other on-car repairs are great for shade tree mechanics but aren't considered to be reliable repairs.

All acceptable repair methods require the removal of the cylinder head.

Depending on the extent of the damage, a Time Sert may work. This is a heavy duty, steel thread insert. When we install these we put the head on a vertical mill so we can precisely locate the repair. It can be done by hand but it's easy to install the insert crooked.

If material has been removed by previous repair attempts it may be necessary to weld the hole shut and re-machine the threads. This is an extreme case but it can be done.

These are the same options I gave and are the right way to do this. My main question is if you are not going to do this the correct way why do it at all?

As far are removing the insert, red loctight must be heated in order to remove the insert. Maybe start with propane and move on to acetylene if you can't get the insert hot enough? Main problem is aluminum is a great conductor and will quickly dissipate heat.

Keep us updated. I'm curious to see what you end up doing.

 

[edged1g]

Can you post some pictures of the current state of the head/insert? Maybe seeing what happened to it will give more ideas.