Re: AC Delco spark plugs
 

R43N is the same heat range as the R43's. The N is for a BB because it takes the longer or extended threads. I believe 3/4". I like the R44S or the R45S for my 69 Z. They run nice and are an original AC Delco plug. S means extended tip. I bet the 44's or 45's would work good in the BB too. https://www.yenko.net/ubbthreads/imag...ins/3gears.gif

Re: AC Delco spark plugs
 

[ QUOTE ]
Marlin....PM sent

[/ QUOTE ]

SOLD!

Re: AC Delco spark plugs
 

My AC book says:

N = 3/4" (19 mm) reach, 3/8" (9.5 mm) thread length