I'm presently running NGK B6S plugs in my 235 powered 3800. My 1-ton is usually run on the highway fully loaded (9,000 gross w/camper). I just pulled the plugs to check it out after w 4,000 mi. trip and they are a nice light tan color.
Besides NGK, over the years I've run AC C42-1, AC C43, and AC 44S. The AC C- whatever, were a commercial plug with much larger electrodes. I have one remaining new one. The last time I bought C-43 it had the same electrode as any other plug so I never bothered to find the C version after that. I have one remaining of that too.
The B6S NGK are the heat range (6) everything seems to use since emission controls came into being in the 70s, Volvos, Saabs, Toyotas, Chevrolet, whatever; BP6ES being the most common. I suppose emission-controlled engines have the same combustion chamber temperatures regardless of combustion chamber design or load? That seems unlikely but they all use the same plug.
Last week I went my to my local NAPA store looking for a hotter plug for my '60 Matchless motorcycle (it has a B8E). I also needed 2 replacement BP7ES plugs for my R-100 BMW motorcycle. I came up empty handed. My NAPA store sells NGK. B8E or B7E didn't cross to anything in their system. BP7ES crosses to a BPR7ES, which is a resistor plug and was unavailable in the regional warehouse. I didn't even ask about BP6ES as I have a bucket full of them. The counterman did mention that when available NGK plugs come in boxes of 8. For something they don't stock I'd have to buy a box.
Is it just MY NAPA store or are non-resistor plugs for older vehicles now hard to get?
