Stripped Spark Plug Hole
11-17-2002, 11:36 PM
#1
Racer
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Stripped Spark Plug Hole
Folks,
i need your help. a plug hole on my L-88 style aluminum heads has been stripped. what's the best way to repair and can i do this with the head on or does it have to be removed? thanks,
:seeya
i need your help. a plug hole on my L-88 style aluminum heads has been stripped. what's the best way to repair and can i do this with the head on or does it have to be removed? thanks,
:seeya
11-18-2002, 12:02 AM
#2
Re: Stripped Spark Plug Hole (thorin)
I see no other alternative then to remove the head.
A Heli-Coil may work, but I would not use one. There are head shops that can do these kind of repairs. There is a guy in Rock Valley IA. that I know can fix aluminum and do it so it lasts. I would guess they would have to
Hele-Ox the hole in and then re-drill and tap it. This would require:
1- a welder who knows what he is doing
2- A machine to allign and drill the new hole.
Not knowing your tools available, I will assume the forementioned is out of your limit. A reputable shop should be sought for this, Welding aluminum in this regard is tricky. Penetration is key, but this will get the head pretty hot as well, (warp). So a deck job may be required. This will be an interesting thread. I am sure there is someone who has dealt with this.
Mark
A Heli-Coil may work, but I would not use one. There are head shops that can do these kind of repairs. There is a guy in Rock Valley IA. that I know can fix aluminum and do it so it lasts. I would guess they would have to
Hele-Ox the hole in and then re-drill and tap it. This would require:
1- a welder who knows what he is doing
2- A machine to allign and drill the new hole.
Not knowing your tools available, I will assume the forementioned is out of your limit. A reputable shop should be sought for this, Welding aluminum in this regard is tricky. Penetration is key, but this will get the head pretty hot as well, (warp). So a deck job may be required. This will be an interesting thread. I am sure there is someone who has dealt with this.
Mark
11-18-2002, 12:45 AM
#3
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Re: Stripped Spark Plug Hole (thorin)
thorin,
I have used Heli-Coils on aluminum heads with great results. Since an aluminum head uses a long reach spark plug hole (typically 3/4"), it provides a lot of bite for the Heli-Coil thread. If you can get a straight shot at the plug hole, you sould be able to do it on the engine. Don't be concerned with the aluminum chips that get inside the chamber, since aluminum melts at relativly low temps, are pretty non abrasive, and will either melt or flow out the exhaust and not do any damage. Although the installer should minimize the amount of chips that enter the chamber by using "greased" tools. Also, the insert tang removal is such that you don't want to drop the tang into the chamber (it would do damage).
The Heli-Coil process uses a new steel thread insert that restores the correct threads, but the old threads/hole must be drilled out and retapped before the insert can be installed. These thread inserts are used in many applications where the parent metal is relatively weak and likely to corrode(like boat outdrives). It is a "mature" process and not "Mickey Mouse".
This a fairly common problem on aluminum heads. Recommend you take it to someone who has done this before, and has the correct "kit", rather than purchasing the kit and learning how to do it yourself. The kits are available at most most auto parts jobbers however (if your feeling ambitous).
Note that plugs should only be removed when the engine is stone cold (on engines with aluminum heads). I don't recommend any type of anti-seize or lube be used on the threads (the wrong kind of anti-seize can actually attack the aluminum, and I have seen others seize as well).
As far as welding is concerned, that is more risky and expensive (IMHO).
Good luck,
I have used Heli-Coils on aluminum heads with great results. Since an aluminum head uses a long reach spark plug hole (typically 3/4"), it provides a lot of bite for the Heli-Coil thread. If you can get a straight shot at the plug hole, you sould be able to do it on the engine. Don't be concerned with the aluminum chips that get inside the chamber, since aluminum melts at relativly low temps, are pretty non abrasive, and will either melt or flow out the exhaust and not do any damage. Although the installer should minimize the amount of chips that enter the chamber by using "greased" tools. Also, the insert tang removal is such that you don't want to drop the tang into the chamber (it would do damage).
The Heli-Coil process uses a new steel thread insert that restores the correct threads, but the old threads/hole must be drilled out and retapped before the insert can be installed. These thread inserts are used in many applications where the parent metal is relatively weak and likely to corrode(like boat outdrives). It is a "mature" process and not "Mickey Mouse".
This a fairly common problem on aluminum heads. Recommend you take it to someone who has done this before, and has the correct "kit", rather than purchasing the kit and learning how to do it yourself. The kits are available at most most auto parts jobbers however (if your feeling ambitous).
Note that plugs should only be removed when the engine is stone cold (on engines with aluminum heads). I don't recommend any type of anti-seize or lube be used on the threads (the wrong kind of anti-seize can actually attack the aluminum, and I have seen others seize as well).
As far as welding is concerned, that is more risky and expensive (IMHO).
Good luck,
11-18-2002, 08:40 AM
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Re: Stripped Spark Plug Hole (thorin)
this list is great! i was feeling pretty low after this happened but now i feel like the fix is close at hand. thanks for the support!
:seeya
:seeya
11-18-2002, 10:50 AM
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Re: Stripped Spark Plug Hole (Allcoupedup)
cannot say for sure but i just spent a load of time and money upgrading the engine with race components. the fellow doing most of the work would've been the one to install the plugs. he's a competent fellow so i'm not suspecting anything sinister here.
i'm contacting him today to share what's happened and see about the heli-coil process. i have a feeling with his extensive experience and tool assortment, he's got just what i'll need.
it's possible the plug wasn't all the way in and vibrating itself out, causing damage along the way. i was driving when i heard the loud exhaust leak and feared the worst (blown head/header gasket) and was actually happy when i saw the plug, still attached to the wire hanging down. i assumed it had not been installed properly and put it back in but it kept turning and turning and turning. you get the picture.
i'm keeping my fingers crossed all will be fine. thanks.
i'm contacting him today to share what's happened and see about the heli-coil process. i have a feeling with his extensive experience and tool assortment, he's got just what i'll need.
it's possible the plug wasn't all the way in and vibrating itself out, causing damage along the way. i was driving when i heard the loud exhaust leak and feared the worst (blown head/header gasket) and was actually happy when i saw the plug, still attached to the wire hanging down. i assumed it had not been installed properly and put it back in but it kept turning and turning and turning. you get the picture.
i'm keeping my fingers crossed all will be fine. thanks.
11-18-2002, 08:01 PM
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Re: Stripped Spark Plug Hole (thorin)
the repair has been done and it looks like a success. i went to napa to buy the heli-coil kit and they knew just what i needed. it was $40 plus $5 for the hi-temp rtv sealant. i figured since i was in the area i'd stop by the checkers as well and see what they had to offer. their kit was $14 so i figured i'd buy it and return the napa kit later but after getting home and beginning the repair, it became clear the napa kit was worth the extra money. better tap and more accessories made the napa kit the right choice.
one thing i figured out during the repair is that if they have kits to repair this kind of problem, it must happen alot, so i don't feel so bad.
thanks to all for your input, i can say that your advice gave me the courage to try this and now i'm a heli-coil expert! :^)
:seeya
one thing i figured out during the repair is that if they have kits to repair this kind of problem, it must happen alot, so i don't feel so bad.
thanks to all for your input, i can say that your advice gave me the courage to try this and now i'm a heli-coil expert! :^)
:seeya
11-18-2002, 08:53 PM
#9
Safety Car
Re: Stripped Spark Plug Hole (thorin)
i knew a guy that cranked the engine over till the intake valve was open (on the subject cylinder), then feed a small hose down into the cylinder through the carb, and hooked it up to his compressor during the repair operation, all the chips flowed out, not in, it worked great, you have to adjust your compressors discharge regulator to supply a modest amount of air flow, don't go ape. Just thought I'd pass it on :seeya
