sparkplugs

[John253a]

just a quick 1

i no there are 2 heads on fe/fc
1 with 5 threads (m14x1.25)=6.25mm thread
1 with 7 threads (m14x1.25)=8.75mm thread

5 thread head use ngk bp4 as standard (use bp5 or bp6 for hot motors)
7 thread head use ngk bp5s (bp6s or bp7s for hot motor)

ive been looking through a few ngk book on number/letter representation
and both the bp4 and bp5s are the same length plug(3/8" 9.5mm), only difference is the electrode thickness on (s) is 2.5mm

ive seen a few running bp5hs (1/2" 12.7mm thread with 2.5mm electrode) on 7 thread heads

Whats people thoughts?
or are the old numbers of bp5s out of date (meant to be 12.7mm thread)

[John253a]

If people arnt sure on p.no
Do they now why there running,
5 thread head 14x1.25 x9.5mm thread
7 thread head 14x1.25x ___mm thread

Another thing are people playing around with the gap on different heat ranges

If been recomemend bp6s plugs with a 0.7-0.8mm gap
When running near stock with twin carbs and extractors

If hot cam bp7s with 0.6-0.7mm

If stock with electronic ignition bp5s 0.8-0.9mm gap
Stock with points bp5s 0.8mm

I was told there us a range for gap as everymotor is different

Just wondering what works for others?