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Old 01-07-2020, 01:57 PM   #37
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Originally Posted by Sapote View Post
Removing plug with hot engine could strip the softer hotter threads. Cold head has stronger threads.

Old plugs might have the protruding threads covered with burned oil and hard carbon; hence it broke loose then jammed by the mentioned dirty threads.

Go slow easy back/forth with lube oil, and best of luck.
Any idea above what temperature aluminum alloy begins to weaken? Or, better yet, does Al alloy maintain its strength until a certain temp is reached and then it weakens?

I googled this a bit and found some threads suggesting that above 350F al alloy weakens. A different guy in same thread says stay below 200C, but that's not far from 350F.


If weakening begins at 350F (~ 176C), that is way hotter than the "warm" temp (by hand feel) that I would typically be trying to remove a spark plug at.

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20mm OD x 12mm ID x 4mm W : Viton O-Ring
3/4" OD x 1/2"ID x 1/16" Thick : Thrust Bearing/Washer

Last edited by LeverThis; 01-07-2020 at 02:02 PM.
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