Reading Spark Plugs

**Jyrki** · 02-28-2010, 02:00 AM

Reading spark plugs is a lost art, at least for me.

I have attached a photo of my Roadmaster plug here. Even I can tell it's not running rich, but is it runing lean? All plugs looked the same

**charley** · 02-28-2010, 07:41 AM

that plug looks ok to me, did you put some anti-seize compound on the threads? I had a nailhead 401 buick with a nitrous system on it and although most brands of plugs looked ok when pulled the only ones that would last more than 1500 miles were the AC plugs.

**saltracer** · 02-28-2010, 09:55 AM

Looks great for a street engine.

**Jyrki** · 02-28-2010, 10:43 AM

Thanks for the replies! No, I didn't use any kind of anti-seize. Charley, what happened to your non-AC plugs? 1500 miles doesn't seem like much...

**Jyrki** · 02-28-2010, 10:51 AM

Speaking of spark plugs, what are you guys using in your straight-eights? Make and model? Nobody carries the original AC p/n anymore, at least not in Finland. I'm using Champion RJ18YC, but I can't recall why? Maybe some cross-reference table specified that one the closest thing to the original.

**charley** · 02-28-2010, 03:56 PM

Jyrki in my nailhead all plugs except AC would start missing. The first few times it happened I thought it might be water in the gas, plug wires, dist. cap, fuel pump I changed them all. I looked at the plugs several times and they still looked ok to me. New plugs would make the motor run great for around 1500 miles but only Ac would last longer. These were the AC plugs that had the center electrode that looked like it had been splined.

**Great Balls of Fire** · 03-04-2010, 03:02 PM

Originally Posted by Jyrki

Speaking of spark plugs, what are you guys using in your straight-eights? Make and model? Nobody carries the original AC p/n anymore, at least not in Finland. I'm using Champion RJ18YC, but I can't recall why? Maybe some cross-reference table specified that one the closest thing to the original.

Those are the right plugs Jyrki.