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| 1986 2.8 V6 - spark plug # 4 just spins (Page 1/3) |
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ArthurPeale
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JUL 11, 03:54 PM
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I've been chasing various gremlins, one of them being a bouncing tach.
having had no idea how old the plugs are, I set about to checking them.
The front ones are in great shape.
#s 2 and 6 are in the same shape as the ones in the front, albiet #6 I could have removed with my hand.
I can't remove #4. I suspect the PO cross-threaded it in the head. It turns, but will not go in OR out.
Let me guess...time to remove the head? That's a project that was coming, just after the fun driving Summer.
This is definitely NOT a case of not being able to slip the socket over the spark plug hex.[This message has been edited by ArthurPeale (edited 07-11-2021).]
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SemperFi18
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JUL 11, 04:54 PM
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Rebuilt GM heads for the 2.8 are relatively cheap. Since Fiero's run so hot I can guarantee you have some hairline cracks in there. I would just save yourself the heartache and drop the cradle, replace the heads, injectors, plugs, wires, cap, rotor and all the gaskets in between..
I started doing a stroker kit 3.1 on mine, while I had it out I pretty much replaced EVERYTHING.. it's too easy and cheap while the cradle is out. I'll have pictures coming of mine soon, just wrapping up the last tedious stuff.
Good luck with the spinning plug.. Your heart had to have skipped a beat when you felt that haha
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Patrick
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JUL 11, 05:45 PM
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| quote | Originally posted by ArthurPeale:
#s 2 and 6 are in the same shape as the ones in the front
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Just for clarification... cylinders 2, 4 and 6 are in the front. Cylinders 1, 3 and 5 are in the rear (closest to the trunk).
| quote | Originally posted by ArthurPeale:
Let me guess...time to remove the head?
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When I worked in a shop a hundred years ago on air-cooled engines, we were able to keep the affected cylinder pressurized with air while we drilled out the stripped spark plug threads and installed a Heli-Coil. I wouldn't be surprised if there's a similar procedure for automotive applications.[This message has been edited by Patrick (edited 07-11-2021).]
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ArthurPeale
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JUL 11, 07:39 PM
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| quote | Originally posted by Patrick:
Just for clarification... cylinders 2, 4 and 6 are in the front. Cylinders 1, 3 and 5 are in the rear (closest to the trunk).
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Curses; yes, of course. Brain did the thing where when you're facing it, that's then the front.
| quote | Originally posted by Patrick:
When I worked in a shop a hundred years ago on air-cooled engines, we were able to keep the affected cylinder pressurized with air while we drilled out the stripped spark plug threads and installed a Heli-Coil. I wouldn't be surprised if there's a similar procedure for automotive applications.
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That would be ideal; I don't really have a place to drop the engine, here, at my apartment. I've been lucky to do the work that I've been doing here, because I can keep it self contained. I couldn't do that with the engine out.
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ArthurPeale
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JUL 11, 08:26 PM
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did some more reading; I'm wondering if maybe I got lucky and the threads are intact, but the body of the plug is the part that's spinning; the hex, separate from the rest of the plug
That would be ideal.[This message has been edited by ArthurPeale (edited 07-11-2021).]
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Mike in Sydney
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JUL 12, 12:47 AM
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Most spark plug sockets have a rubber sleeve in them to grasp the porcelain insulator on the plug. Occasionally, when changing the plug on one of my bikes it will feel like the socket is spinning freely. (This sounds like what you are describing.) For me it's because the screw-on terminal on the plug extends into the area where the socket extension head is, This holds the socket just high enough for the shoulders on the plug not to engage the shoulders in the socket. Pulling the extension out of the drive hole a bit to where it isn't fully seated in the socket works sometime as does pulling off the screw-on terminal.
If you can seat the socket firmly on the shoulders of the sparkplug you should be able to tell if the hole is stripped by trying to turn the plug and socket with your hand. If it turns easily in either direction chances are the hole is stripped and you'll need a heli-coil or equivalent.[This message has been edited by Mike in Sydney (edited 07-12-2021).]
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Patrick
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JUL 12, 02:53 AM
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| quote | Originally posted by ArthurPeale:
This is definitely NOT a case of not being able to slip the socket over the spark plug hex.
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| quote | Originally posted by ArthurPeale:
I'm wondering if maybe I got lucky and the threads are intact, but the body of the plug is the part that's spinning; the hex, separate from the rest of the plug
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I don't know about anyone else. but you've certainly got me confused. 
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theogre
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JUL 12, 11:45 AM
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| quote | Originally posted by Patrick:
I don't know about anyone else. but you've certainly got me confused. |
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Yup Because spinning plugs shells are very rare to impossible. Shells are most of the metal part w/ threads. Go and look at plug design at many plug maker sites. Example: https://www.autolite.com/do...r-core-attibutes.pdf
IOW shell broke mean the ceramic etc pulls out.
In Cast Iron heads, Most times...
the plugs break and leave the threads and ground arm.
Plug threads strip and plug the thread in the head.
most times the cast head is good but may need thread chaser after plug is gone. Problem here is many standard threads tools won't fit plug holes on many GM heads.
Spinning and won't move is much harder to guess exact problem til plug is removed.
Compress Air on intake side may help keeping crap out when you wreck the plug etc.
But be careful because plug crap staying in the engine can quickly destroy it. A bore scope is good here to check for left over garbage.
"They" do make plug thread repairs for heads but much harder to install in cast iron heads.
Most strip plug threads are in Aluminum heads.
These are made for this job and not just simple "helicoils."
More You need right length and type for tapered plug. ------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave
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ArthurPeale
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JUL 12, 03:31 PM
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| quote | Originally posted by Patrick:
I don't know about anyone else. but you've certainly got me confused.
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I'll try to do better at explaining - certainly easier with visuals.
Most times with the front plugs, people complain about not being able to remove them because debris and rust make it very difficult to slip a socket over the hex.
In this particular instance, I can confirm that the socket has slipped over the hex.
what I thought - what I hoped - was that the hex part of the assembly was spinning separate from the threaded part of the assembly, but the gist I'm getting is that it's all one piece, is that accurate? I know on some spark plugs they can be separate.
If you put a finger on the top of the plug, it will wiggle, just a little.
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ArthurPeale
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JUL 12, 03:33 PM
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| quote | Originally posted by theogre:
"They" do make plug thread repairs for heads but much harder to install in cast iron heads.
Most strip plug threads are in Aluminum heads.
These are made for this job and not just simple "helicoils."
More You need right length and type for tapered plug.
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I thought Fiero heads were aluminum?
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