Butt dyno…
I use these on my XJ6 and Mk2. I just ordered three sets from my favourite online wholesaler. New ones are made in Thailand, old ones in Japan. The way the world is. Paul.
Many thanks so far,
so much input, and information. I got what I wanted to know for my 61 most original car which will probably not be driven very often. It is all about originality. Not everyones steak but this is the target for this specific car.
I will install the N5 MADE IN ENGLAND.
Having searched the drawer and old tool kits I found most N5 MADE IN ENGLAND but also spotted two variations.
One is black and another one has even MADE IN U.S.A
Did someone say the black one was an early model for the XK and the USA production is what? Just to complete the topic.
Many thanks.
I turned up two more Bulletins which explain where the N-12 comes into the equation. All 3.8’s had N-5 plugs until December 1962 (engine R9528) and they were replaced with N-12Y plugs for the remainder of 3.8 production. The plugs for the 4.2 cars were N-5 and changed to N-11Y in March 1967 (7E10447). The changes were due to reports of plug fouling at low speeds.
Same experience here. In my BMW M52 engine I had 3(!) champion plugs fail within 20000 miles, always had cracked isolators arround the center electrode. Never had any such problems with other brands.
The AJ16 didn’t idle very well when I got it (from Itlay). It had brand new Marelli plugs installed. I replaced these with brand new BOSCH - no change. Then thought I’d give the Champions a try as they were origianlly fitted by Jaguar, but idle got even worse. Then I found well used NGKs in the bottom of the box, installed those and to my amazement I had perfect Idle. I still don’t understand what has happened here, I never had an engine that sensitive to the plugs. I have the feeling something else is wrong (possibly the coils?) and the spark plugs only tip it over the edge.
Cheers,
Harald
for Maikel: if you search the XK120-140 forum in the archives by sparkplugs for xk120 you will find a lot of info on the originality and history of the early Champion spark plugs fitted at the factory, even including box descriptions. The XK120, 8-1 comp ratio was fitted with the Champion NA8, black body and Made in England (there were silver body and made in USA but those are not factory fitted), the XK140 with the N8B from May 1954. The N5 was the new number system from July 1957. The N5C (copper) followed that. Nick