The Cessna 120-140 Association Forum

Is the long reach Tempest UREM37BY spark plug safe to use on a C90 engine with Millenium cylinders? The Tempest application chart says yes, but I have heard rumors about the long reach plugs being too close to the piston.

I can’t speak for there use in a C90 but they work quite well in my O200.

7985 wrote: ↑Fri Sep 04, 2020 10:46 amI have heard rumors about the long reach plugs being too close to the piston.

I am not aware of any issues. I don't think there's any significant difference. The increased compression comes from greater displacement, not a smaller combustion chamber.

piston at TDC use a 1/2" wood dowel rod measure to cylinder base at plug and remember theirs a copper washer to add.