Thanks. There's a metric boatload of clearance between the dished piston (at TDC) and the plug hole - literally inches, lol. so interference wouldn't be an issue. I presume the plug ideally will sit so the last (or first if you will) thread is flush with the combustion chamber face - neither recessed nor protruding - only the electrode protruding into the chamber.

This I can measure. Correct heat range? Trial and error?

The R44T would be recessed nearly half an inch looking at the hole from the combustion chamber side. Again - clearly not even close to correct.

..

Aside .. I wonder if this was the original reason this core went to scrap. Wrong plugs (somebody going by the book) either it wouldn't run, or got messed up.






Last edited by Jim Tyson; 08/15/2016 2:40 PM.