• If you like antique engines, vintage tractors or old iron, please register and join us. When registering, please provide your CITY and STATE in your location!

stuck spark plug in aluminum head

dkamp

eMail NOT Working
If it's turning 1/16, that means you've got just some stuck to it... but it may be just enough at the cylinder end to bind, don't force it. Keep running the engine... start it, run it at governed speed for long enough for it to get hot, then shut it down... drip water on the plug steel to shrink it... repeat.

Pull the head, put it in the bead-blast cabinet, and hose down the end of the plug. If there's ONE thread that protrudes into the combustion chamber, and just a LITTLE carbon soot on it, you'll have a stuck plug. Bead blasting may clean enough off to let it go.

the other way, is bust out the center. I've put aluminum flatheads with seized plugs in the Bridgeport, centered the spindle to the plug, and drilled it out a little at a time, till there was just a thin band of plug steel body left... then I stuck a triangular air file in the hole and addressed the remains in three places, then a small pin-drift and a hammer, and knocked the offending pieces out, to find only one damaged turn in the thread.
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
well its out, heated the crap out of it with the oxy/acy torches and broke out the 1/2" breaker bar back and forth just a little more each time untill it was out. I bought a chaser and i think i will be fine after cleaning the threads up. and a big 10-4 on the antiseize, i use that stuff on just about everything!
 

mcostello

Registered
Had a Never Seize school at work, Honest. The Sales Man said, when You take apart something that You KNOW You put Never Seize on when assembled, and it is not there, that is proof it was stopping galvanic corrosion. I have only seen it once, and I was a firm believer before this happened.
 

KidDynamo

Subscriber
Last Subscription Date
11/10/2018
I didn't read this whole thread but two things:

1) Don't use anti-seize on spark plugs in an aluminum head. Thank you Onan service bulletin.

I never had any problems with aluminum head spark plugs until I discovered anti-seize at the early stages of my marine engineering career, and then I had repeated problems with costly and time consuming problems. Just the anti-seize alone was enough to cost me numerous threads that had been perfect.

2) When a plug in an aluminum head turns just a slight bit and then jams, there is a strong possibility that what is hanging it up is carbon crud stuck onto some threads that are sticking into the combustion chamber. The plug may turn slightly and then the crud packs down and stops further turning. Not a big problem on iron heads.

Further turning by force, with heat, or whatever, can strip the female threads in the aluminum head.

Removing the cylinder head, cleaning the threads and then unscrewing the plug may be the solution. Then, while the head is removed, figure out how to shim the plug to not have threads exposed in the combustion chamber.

Replacing the head gasket, even if you have to search for it or make it, can be an easier problem to solve than restoring the threads in the head.

It took me far longer than it should have to figure out that aluminum heads and anti-seize are not compatible.

Perhaps others can chime in as to the efficacy of this info. I see as I edit my post that you've had a measure of apparent success in removing the spark plug. Great !!

A local guru on aluminum heads says to just give them a shot of WD-40, install the plugs, and off you go.

Good luck!:wave:
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
I had this engine completely apart 10-12 years ago, it was a boat anchor when i got it! there are no threads protruding past the head into the combustion chamber and i couldnt get this plug out back then. the other 3 were a bear but i did get them out. they have had antiseize on them for at least a decade and posed no problem upon removal. the engine had been run for a few hours before being put into storage. that being said i will take my chances and neverseize them! threads cleaned up and the plug torqued to spec.
 

Power

Registered
Tip: Reduce Torque When Using Antiseize #566812 07/16/05 06:42 AM
OP

Antiseize compound is a lubricant. Accordingly, you need to reduce the torque on spark plugs and fasteners about 30%. This will help prevent stripping threads, particularly in aluminum block engines. Use antiseize sparingly. A "half a pea size" drop on spark plug threads is all that's needed. Allow thread rotation to spread the compound. High temperature nickel compound is the product of choice. It's harder and keeps dissimilar metals apart.

ASME torque convention is dry (without lubrication), unless specified otherwise.
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
Tip: High temperature nickel compound is the product of choice. It's harder and keeps dissimilar metals apart.
This is likley key part here and is the only thing i use anymore.
 
Top