While I'm grateful that small block Mopar engines have affordable aluminum cylinder options, I never really liked the way that the spark plug's entry into the combustion chamber was implemented. I looks like a machining process step was skipped resulting in the recommended RC12YC spark plug being sunk and shrouded.
Yesterday I was replacing the plugs in my Ram and looking at the plug I had an idea.
RC12YC have a .750" thread while the 5.7 Hemi plug (NGK LZFR5CI) has a 1" thread.
What's worse, to have a sunk plug with the shrouding and ~0.300" exposed aluminum threads or have a plug that makes full use of the available cylinder head threads (improved plug cooling?), bump in compression with a comparable ~0.300 of exposed plug threads?
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