fuel and spark plug info

[JohnBM]

I have an FE with original 138 grey motor. I'm at a loss at the moment as to the correct fuel I should be using. A carby mechanic of 40 years experience tells me to use something like BP Ultimum, Octane rating 98.2. Club members are telling me, no, and to use a lower rating and correct spark plugs to cope with the unleaded fuel. The plugs in the engine at the moment are NKG and the number on the box they came in is 2911.BP4.
Help!
Regards,
John

[John253a]

Bp4 is for 5 thread head
Bp5s is for 7 thread head

U need to remove no1 plug and get a torch and count

Now here's where it get confusing (other then heat rating numbers, lower = hotter, higher = cooler)
I was told
bp4 is m14x1.25x 3/8" in length and heat of 4
Bp5s is m14x1.25x 1/2" in length an a bit cooler at 5

But going off the ngk web site you need a bp5hs
http://www.ngk.com.au/sparkplug.php#

I asked the same question 3 weeks ago

http://fefcholden.org.au/forum/index.php/topic,20652.0.html

As for fuel I use 98 oc as it's the closest octane ratting to leaded fuel then I put in the additive as I don't have my head set up with hardened valves and stallite inserts yet

There are many that use 91 oc and it runs fine

[FCGos]

If the engine is in standard form it will be have a relatively low compression ratio when compared to later model engines and the lower octane fuel should be satisfactory, however with the absence of lead to aid in lubrication you will need to use an additive to help prevent any undue vale seat or guide wear.

Cheers Wayne