[xj-s] Spark plug question

XJ-S
1

I’ve been running NGK BPR6EY resistor plugs, chosen 2 years ago with
advice from this list.
More recently, someone suggested that my car (pre-HE) may do better with
the
“original Champions.” My 1975 edition ROM says Champion N10Y. Champion
no longer makes this plug, recommending N11YC instead. However, they
recommend
the RN9YC (resistor plug) for the 1976 XJ-S.

I believe that in addition to being resistor, the RN9YC is also a
“cooler” plug… isn’t that what the 9 means?
As I recall, the “hot” vs. “cold” plug has to do with how hot the tip
will get, and hotter plugs are
better for older engines. Or do I have this all wrong?

So, somebody help me out here. In my view the issue is not Champion vs.
NGK, but whether to go
for a hotter or colder plug to reduce fouling.

Ed Sowell
76 XJ-S (pre-HE)

2

Thanks, Greg. I found the NGK technical info Web site
(http://www.ngksparkplugs.com/techinfo/spark_plugs/)
and learned that SMALLER number is HOTTER, so the BPR6EY plugs I now have are
pretty hot.

But who knows, when I get the idle air hoses replaced (right one is soft as
jelly) it may
no longer have a fouling problem!

BTW, when we last talked you said some people have gone back to the Champions
to clear up ignition problems.
Which Champion was that, RN9YC or N11YC, or some hotter plug?

Cheers,

Ed

Coventry West wrote:> “Edward F. Sowell” wrote:

(snip)

So, somebody help me out here. In my view the issue is not Champion vs.
NGK, but whether to go
for a hotter or colder plug to reduce fouling.

Ed,

IIRC, a hotter plug is the way to go to reduce fouling, if present.

Best regards,

Gregory Wells
Coventry West, Inc., Atlanta, GA
New, Rebuilt, & Used Jaguar Parts
http://www.coventrywest.com
800-331-2193 x103