Thanks Bill couldnt remember which ones, now on the 289 its not saying its any good for a 20 engine which the blues worked good for me along with my 45 and 60 engine
The 289 plugs are supposed to be the same heat range as the blues so it should work on the 20 motors. O'Donnel told me they just changed to a better hermetic seal on the plug. They said some of the blues had a leakage problem but I never had a problem with them.