77 XJ6C ran smoothly for weeks after changing plugs & wires. #4 was badly oil fouled. Just changed oil, Castrol GTX 20W50 and NAPA 1231 (Wix) Filter. Added oil too fast at one point and filled the valve cover. Of course this is on the Exhaust side, so no valve seals. Missed badly upon start. Pulled #4 and it was fouled but not the only cause of the miss. This time #6 and who knows maybe more. Thoughts from the gang ?

 

That seems odd, as the valves will be flooded with oil when it's running, so how fast you add oil when filling the engine should make no difference. Sounds like you have bad rings or valve stems to be oil fouling the plugs? How much does it use between changes?

 

I agree.

Those cam covers are flooded with oil with the engine running.

Forget the filler cap, GUILTY, and the mess in minutes is HUGE.

Badly worn valve guides???, maybe, BUT, they usually lay a smoke screen with that problem.

 

I agree with much of what you all have to say but a few concerns. My engine is showing over 100 K Miles, so yes, wear in every area. But it only had some blue at start up. Once warm it went away. As I said it was running very smooth up UNTIL the oil change mistake. I also doubt that the amount of oil normally flowing through the galley is nowhere near that of a completely full valve cover. Another curiousity. Looking at this video from a trusted source it sounds as though there are normally seals on the Exhaust Side NOT Intake side. I'm confused. .

 

Too long ago, dont remember, but all 12 got seals on assembly.

100k miles, just run in.

Daughters S2 XJ6 is nudging 500k kms, and still sweet as. She runs it HARD.
The V12 (1976), just topped 655k kms, and untouched from Coventry.

Some blue at start is "usually" rings, with stem seals a close 2nd. Low mileage for a 45 year old anything, a good long hardish run would probably do wonders for the whole thing. They are a race engine after all.

We still do a quick 400km round trip, just for lunch.

 

Thanks ! Clean plugs, a good run & lesson learned, may well be the best way to go.

 

You are up there and I know little of your land, but a road trip to Vegas, always a winner. We fly in, the Jag dont swim so well.

I understand some owners fear of using a Classic, but dont agree.

The more you use them properly, the longer they last.

Different beast I know, but when the urge takes me, the Whale, AKA the MK X, comes out to play, and that thing is at some insane mileage, the odometer stopped 30 years ago, who cares. Sooted sparkers goes with the 3 carby arrangement, but a good hard blast through the streets, sweet as.

 

Deleted.

 

Threw in some new plain NGK's and she runs smooth. I know some are saying at one point all valve stems got seals but have my doubts on my 8L. I filled the exhaust side cover to the top and all 6 plugs were fouled to one degree or another. She runs great now ! I also picked up a $20 pneumatic plug cleaner from Harbor Freight. Will clean my Denso Iridium plugs and keep them on hand. Wonder if Iridiums, with that tiny wire electrode foul easier ?

 

The plot thickens, then clears, I need a DRINK.

Fancy, huge $$ spark plugs in these engines are a huge NO NO.

Standard, as in, NOT even Resistor spec, are all that is needed, and the Ignition system is designed for them only.

Both my AJ16, much later engine, ran like crap with "fancy" spec sparkers. Back to standard (albeit resistor) spec, and sweet as.

The MAIN reason is that the older engines ALL used oil BY DESIGN, some more than others. I know of many who have chased the elusive NO oil usage on that XK engine, and none I know of have really succeeded. The later stuff does NOT use oil (very, very little), so the crazy emissions specs are met, we hope.

Stick to standards every 40K kms or so, and enjoy. Still drive to Vegas though, why not??????

 

I found the same years ago in an E Type. Fancy Bosch platinum plugs fouled, the plain jane copper plugs worked the best.