ulh spark plugs....heat range

[mark59]

even'n folks, i have a mildly stroked ULH at about 7 to 1 compression with S&S alum heads, 14mm plug size. i'm looking for input per what brand and number plug to run. thanks folks....Mark

[Frankenstein]

I built a 84" stroker a few years ago and used NKG B6L's, same as you'd use in a Panhead. They seemed a good choice.
Dick

[mark59]

thanks dick, I had been running an NKG #7 and plug is a bit too warm, insulator is too clean while i am running a tad rich,(45 slow jet in a harley CV carb) a #6 may be about right. i just put 200 miles on today on an old pair of Harley #7 plugs. i will pull the plugs tomorrow and see how they look, was trying to see how cold i could go and work my way warmer. surprisingly it ran very well with all conditions including slow back roads and 70mph highway.

[Frankenstein]

You should do a google search on reading plugs, Gordon Jennings has done articles on the subject as well as others.
Here's a couple of results:
http://www.strappe.com/plugs.html

http://www.4secondsflat.com/Spark_plug_reading.html

The crux of the matter is to read the central insulator for mixture, and the grounding electrode for timing.
I've been riding and burning up BTSV's for 40 years, Love 'em, can't beat the torque
Good Luck