Maybe helpful to newbies...Alulminum threaded spark plug holes are delicate and must be treated with respect. :laughing: Some readers may have had to replace a head after a damaged spark plug hole or unfortunate repair. IMO (and the experts) here are some reasons such threaded holes can be damaged. Cross threading: the plug is not aligned properly when starting or is misaligned before the leading threads are engaged. Carbon build up: the tip is subject to carbon build up which forms a ring too big to unthread without interference. Rust , dirt, debris drop in. Water puddles around the plug (corrosion). Failure to blow out aroud the plug before removal (shop air or bicycle pump).
I like to be able to finger tip thread the plug ALL THE WAY IN. This may seem overkill, so at least thread it all the way in with a socket and STRAIGHT extension (no handle). There is a tool recommended for cleaning the threads if you encounter resistance- a thread CHASER ($7 up).They are tapered end with cutouts (gashes) to collect carbon, dirt, and rust. Above these cutouts are threads that match the threaded hole, but are dulled compared to taps and are meant to roll aluminum back into the thread configuration without removing it. (Taps will remove material) Remove the chaser and clean out the cut outs. Use lubricant . The clean hole should look shiny.
Develop a careful technique when threading so that the socket extension stays aligned with the plug. It is easy to create an angle with a socket handle . Especially if you have to force the plug through damaged or dirty thread holes. Power driven tools (air or electric) are no-no's. Apparently removal with these can damage threads (not used so don't know)
Pictures...
I like to be able to finger tip thread the plug ALL THE WAY IN. This may seem overkill, so at least thread it all the way in with a socket and STRAIGHT extension (no handle). There is a tool recommended for cleaning the threads if you encounter resistance- a thread CHASER ($7 up).They are tapered end with cutouts (gashes) to collect carbon, dirt, and rust. Above these cutouts are threads that match the threaded hole, but are dulled compared to taps and are meant to roll aluminum back into the thread configuration without removing it. (Taps will remove material) Remove the chaser and clean out the cut outs. Use lubricant . The clean hole should look shiny.
Develop a careful technique when threading so that the socket extension stays aligned with the plug. It is easy to create an angle with a socket handle . Especially if you have to force the plug through damaged or dirty thread holes. Power driven tools (air or electric) are no-no's. Apparently removal with these can damage threads (not used so don't know)
Pictures...
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