Seized sparkplugs. What to do?

[Fast 58 BSA]

My alloy head has some very old and very stuck sparkplugs in it. How to get them out? Should I heat the entire head in the oven or just area around sparkplug? Can I use a freezespray on the plug itself after heating the head or do I risk cracking the head? Or take it to an automotive shop and let them deal with it?

[saltbox Alf]

Hi mate, see you have the valves still in , my cure for stuck items is a soak in diesel for about a week , great for long standing seized engines, fill up the combustion chambers and let it stand. as for heat, you should heat the whole item ,as local heat can cause warpage or stress cracks. Patience is the byword, they will come out, eventually!!

[bsa-bill]

Hi there
Alloy head - stuck plugs, lots of people have had this and stripped plug hole threads issues, so take heart that if the worst happens you can get the holes fixed with Helicoil or other insert and end up with a perfect head again.
Alfs suggestion sounds spot on for first action, just keep soaking them and give the stuff time to creep in

[Fast 58 BSA]

Alright, will attempt diesel soaking and let it sit in it for a good week then see if I can get the buggers out. Thanks for the tip

[RichardL]

Why diesel instead of a formulated penetrating oil?

[bsa-bill]

 Diesel has good creep and unlike some penetrating sprays it does not dry off , it leaves a good lubricating layer, just the job for soaking stuff, this is not to say it is better I still like Plus-gas for immediate jobs.
I almost said Diesel is also cheaper but the way things are going.......................

[Fast 58 BSA]

Im going to give penetrating oil a go first. Let it sit for a day or two then see....

[muskrat]

 G'day Fast58BSA,
                         if soaking fails I would suggest punching out the porcelain and electrode then run a 12mm drill (Tapping drill for that thread is 12.8mm) down the hole to weaken it's grip. Most stuck plugs are caused by carbon build up at the end of the thread, so you could drill or dremel the end till you just start to see the thread in the head. Good luck.
Cheers.

[a10 gf]

Lots of suggestions here! I've had some very happy results with freezespray against stubborn 'things': heat up the parts as much as it can take, also spray some wd40 or whatever, then use a good dose from the electronic cooling aerosol can directly and locally on the seized part, in this case the sparkplug. The sudden metal contraction trough an -30c ice shock can do do the trick.

Good luck and tell us how you finally did it.

[Fast 58 BSA]

Alright, here is an update. Applied penetrating oil for three consequtive days to soak it good. Still stuck. No movement whatsoever. Anger is building so I take  quick breather and decide to try muskrats suggestion. Knocked out the electrode and porcelain. Carefully drilled to weaken the remains. And....the top part of the plug broke off when I applied some muscle. So, I guess Helicoil is my only option...the buggers look to be 40 years old and appear to have "married" to the head. Anyway...problem is solved, but I was hoping to save the threads. C'est la vie.

[muskrat]

 Hope not lost yet. Tapping drill is 12.8mm or 1/2". If you run that down the hole you should be left with a coil that can be prised out with a sharp scribe then griped with long nose pliers and unwound out of the head. Just like removing an old helicoil.
Cheers

[bonny]

i don't think you can beat a bit of heat , its worked for me nearly without fail over the years , if you heated the alloy around the plug or remains of the plug , it would expand more than the steel of the plug body and let go of its grip on it. is there anything left of the plug you could weld a bar onto and twist ?

[a10 gf]

i don't think you can beat a bit of heat

agree, and with the additional use of refrigeration spray one gets even more chance of success. But all can still go well, use patience as the main tool.  Muskrat, thanks for that great picture

[Fast 58 BSA]

Muskrat, thanks for the encouraging picture  .
I am going to give the tapping drill a go first. Bonny & a10gf, thanx for suggestions. Haven't had any success wity applying heat yet, but if my tap drill attempt fails....

I'll give it a go this weekend and post an update