Hey guys, i am getting ready to buy a set of plugs to actually run the motor on and wanted to make sure i am getting the right one. They holes are at an angle and they dont look tapered so i would think a gasketed plug is correct. Also whats available for heat ranges? I am running a 9.8:1 compression with a UD 272/282 238/248@.050 and might want to stay on the cooler range of the plug spectrum to help with any possible detonation issues. Thanks guys!

Daniel

My 390 castings use a R44XLS.

The XLS must mean extra long...
There is an R44TS, which is a tapered plug.
The other is an R44S I think, they are gasketed but short threads.

Yeah, these holes are pretty darn deep. I think the ones i had as spares were Autolite 403. I will check on the extra long ones though and see how they come out. The one i had have a pretty long (5/8 or so?) threaded portion on them.

Daniel

Been running R44XLS in my 215's. Should be a good starting point then you may have to go up or down one heat range.