what are good spark plugs to run on a 340 and gapping ?
............So the op is just supposed to pull a plug number outta thin air I presume?........kim......
Which is exactly why I gave the answer I did. Usually, 99 times outta 100 whatever the factory plug is will either be dead on or get you real close. After that, brand is personal preference.
I simply assume since the OP has sense enough to post on a forum, he can look up a plug application. That way, he can make his own decision based on his own preference to brand, rather than listen to a bunch of total BS on a forum where most don't know what the hell they're talkin about.
After all, a spark plug is pretty much a spark plug. People think there's a magic plug out there that will unlock 50 HP. I got news. It ain't happenin. Most anything besides a standard single electrode plug is a gimmick to get your money. Above and beyond that, "I" would not recommend a fancy platinum or the like for any older engine like these. Just not necessary......unless you just feel like wastin money.
Anyone saying one plug "sucks" over another obviously has limited experience, or is simply spouting out of their back side. There's probably only about 3 or 4 plug factories in the world that actually make the plug, so that means chances are the plug you thing is good might be the same plug you think sucks.