ORIGINAL: blw
Something that W8YE suggested for my 46NT- try either the OS A3, or Tower plug if you are using an OS 8. That was a world of improvement in my engine. I'll never go back to the OS 8.
Barry,
The right plug range for this engine is medium heat. The OS A3 is too hot and you need to adjust the engine significantly richer to avert detonation (what a lean-run really is).
This would make the OS #8, Enya #4, Rossi R4, Novarossi/MVVS C6-S, K&B-1L, the newer Tower and other plugs suitable.
The OS #8 has been changed lately and not for the better... Sigrun mentioned this in two recent threads.
He says they are only like the older OS #8 in their appearance, but are lousy from every other aspect...