AC Delco Spark Plug suffixes

[Wayne M.]

Can someone refresh my memory on meaning of the various N, R, T, S, L, X's following the Size (eg. 4 = 14mm) and heat range (eg. 2=cold, 6=hot).

TIA

[Dave S.]

Re: AC Delco Spark Plug suffixes

Wayne,

N = Big Block

R = Resistor

T = Tapered seat as in the later peanut plugs(around 70 and up)

S = Extended Tip

Not sure what L and X mean.

[Duke W.]

Re: AC Delco Spark Plug suffixes

From my '94 Vintage AC-Delco Spark Plug catalog.

N = 3/4" reach, 3/8" thread length

R = Resistor (sport vehicle plugs)

T = taper seat shell design

S = extended tip or 7/8" moderate long reach or 23/32" long reach

X = wide gap (HEI)

XL = 3/4" reach, fully threaded

[Jeffrey S.]

Re: AC Delco Spark Plug suffixes

Wayne:
N= extra long reach (3/4 inch reach with 3/8 thread length); R=Resistor; T= tapered seat (no metal gasket is used); S= extended tip; L=long reach- 7/16 in.; X=special gap (usually wide gap).
Hope this helps.
Jeff