Any thoughts on the best plugs for the V12 S3?

I took mine out to check the compression for each pot and re-gapped them but they were worn and as such may need replacing.

Also what gap would you chaps recommend? The book says 25 thou which I set them to (they were more like 35 to 40 thou when I took them out) but since then the engine has run lumpy, it was fine before

Cheers
Shaun

1973 S3 V12 Roadster (and will get picture up soon!!)

Submitted by NE52-32043 on Tue, 01/07/2003 - 13:31

Pascal,

I think that the manual's stated 12K miles is very low. On our engines, 20K to 30K for standard plugs is probably more realistic. Platinum plugs are supposed to hold up much better and last longer. However, you run your car hard. The wear that high speed/racing induces on all parts of the car cause parts to wear out sooner. It's a good thing you're changing plugs now, especially with so many driving events coming up soon. You should talk to the shop about the NGK Platinum plugs. You may see better performance overall from them.

Steve Weinstein, JTC-NJ
'72 E-type 2+2
'89 XJS Coupe

Submitted by pascal@jcna.com on Tue, 01/07/2003 - 12:36

speaking of plugs, how long are they supposed to last ?

manual says 12k... I recently realized that mine have been on for just under 2 years and... 25k ! Of course, the MSD ignition is probably helping by sending enough juice to fire them anyway but may that explains why idle isn't as smooth as it used to be and why they seem to foul when the engine is real hot and sitting in traffic or restarting...

Car is in the shop this week, pre Road Atlanta ( this saturday) check and new plugs are on the list... I'll see how it runs then and what the old ones looked like... but I'm curious to know how many miles do other series 3 owners get out of theirs...

Pascal Gademer
72 E-type 2+2
00 XKRCoupe
99 XJR

Submitted by NE52-32043 on Tue, 01/07/2003 - 12:13

Shaun,

I have a '72 Series 3 V-12. When I changed my plugs last spring, I used Champions -- direct replacment for the original. I gapped them at .025 and they work just fine. I used NGK's (TR5's with grooved electrode) in my XJS recently, and like them a lot. I think the next time I change the plugs on the E I will use the NGK Platinum plugs if they are available in a size to fit. Some people like the standard Bosch Platinum plugs, though there are mixed reviews on the +4's on our older cars.

As far as the lumpiness goes, did you go back and check that all the wires are connected properly? Old wires can break when you remove them or you may think they attached themselves to the plug properly, but did not. I replaced my wires with 8mm Magnacor's and like the performance. You can check continuity on the wires with a timing light with induction pickup -- just move it from wire to wire and look for any that are either not firing or are firing intermittently. Also, you may want to pull the distributor cap and check both the cap and rotor to be sure they are in good shape as well.

Hope that helps. Let us know what you find.

Regards,
Steve Weinstein, JTC-NJ
'72 E-type 2+2
'89 XJS Coupe