Spark Plug Indexing V-12 HE

Yes you are correct. As I work down the line guess what I’m doing today? I spent 2 hours last night fighting to change four spark by the throttle pedestal. I swear they were welded in there and looking fairly cruddy when they came out.
As I work towards the cruise control bellows I’ll replace the next four and swap out the distributor cap and rotor and also Oil felt pad. I’m just trying to figure out if I’m going to clean the distributor and grease the weights and springs in situ or on the bench. Sounds like a fun job regardless.

Take it out, in the end much easier. Check that your vacuum advance capsule holds vacuum, and if you need to change it, you’ll be glad you pulled the distributor; it is held by a miniature roll pin. If you need one, British Vacuum Advance is the best (no affiliation), they build them to correct spec.

If you need to disassemble centrifugal advance, definitely easier on bench. I had a bit of trouble getting my distributor back in perfect, took about 8 tries. Its too easy getting one tooth off. Just a lesson in back support. And take photo of which way rotor is facing before you pull!!!

+1 on British Vacuum Advance, a rebuilt is much higher quality than aftermarket new. Very easy to swap on bench too. If you still have original, def rebuild.

Together with these improvements, you’ll probably have better pickup/performance. Just make sure your base timing is spot on (18BTDC at 3000rpm with no vacuum advance)

Well finally got the cap off , it was stuck on there good. Rotor lifted right off but where’s my felt to oil?
Sounds like another conversation with my factory trained Jaguar mechanic who was asked to clean and overhaul the distributor when I bough the car. Every spark plug has been a fight to remove . They were on there tight and gummed up looking. I guess I was due after all.

You’re lucky the plugs weren’t rusted/seized enough to ruin the aluminum threads in the block! I would definitely chase those threads and use a lot of carb spray. A bit of anti-seize on plug chase threads after cleaning can’t hurt either. Or oil. Or something.

I seem to have some bad threads on 3A in the head, i think from old plugs left in too long. Not stripped, but when plug was halfway in, it suddenly took 8+ftlbs of torque to turn it, but then it got easy again until seated. Chasing threads helped, but its still not 100% finger tightening all the way like it should.

No kidding, here’s what I’ve managed to pull out so far.

Felt wasn’t there originally, it is recommended to add it to hold some oil.

Yeah, this is Kirby’s recommendation once you switch from the failing grease to synthetic oil.

A little wad of cotton will do, actually.

I’m having a biotch of a time getting 3B back in. I don’t want to force it. What is the best way to clean the threads on the head without sending a whole bunch of crud down the hole. It seems to take a few hands turns but then stops. So I back off . I have some anti seize, synthetic oil, Wd 40 and carb cleaner. (You name it) Can I just hit it with a good spray of carb cleaner?

Like i said, a spark plug chaser, and carb cleaner.
Crud will fall into cylinder. I don’t understand why some are freaked out by that, a bit of dirt and grease will simply incinerate in there.

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Thanks sounds good. It’s weird since it wasn’t one of the difficult ones to remove.

Probably carbon build up left behind.

You can put some grease on thread chaser grooves which will help catch the junk.

Its just cleaning threads, no metal shavings created.

Shotgun cleaning brush. Need to get the right size, I think it’s a 20 gauge. Just screw it in, then unscrew it back out. And yeah, a lot of crud will end up in the hole. Used compressed air to clear as much as possible.

Thanks for the tip. Hopefully between this and Greg’s thread chaser ideas, I’ll be armed for round two or is it three.
You know I started this thread about indexing spark plugs and gave up on that idea after the first day. 3 hours of cleaning up the valley and only changed 3 spark plugs. I felt lucky to get the old ones out and new ones in without too many issues
I swear I fiddled with that one problem plug for 11/2 hours alone. I had no idea that AC compressor weighed as much as it did. That was a bear to move as well. I think it much have been designed by the Sherman Tank company. Two plugs to change today under the compressor and sort out 3B plug. Not sure if I rate it as a difficult job so much as one that will wear you down and try your patience to say the least.
The distributor was another story. Getting it out cleaned and lubed. The rotor arm lifted with no fuss.
I found a new felt pad from my Dremel tool polishing attachments. I soaked it in synthetic oil and it popped into the top of the distributor shaft no problem (perfect fit). I’m just going to clean up my rotor arm and reinstall it. My new one didn’t arrive as of yet. I was lucky to find a brand new distributor cap in my spare parts box that Mark White a former JL’s XJ-S poster had sent me after he sold his car. I noticed the spring loaded carbon widget at the top center comes down a lot more the the old cap. Do these things where out over time? Aside from that the old cap appears in good shape.
Back in for round three today and starting clean up of valley , vacuum hoses , plug wires and fuel injector wiring harnesses.

Absolutely: I’ve seen some do neglected, the carbon brush was gone, and the spring was the main conductor!

Just another reason distributors are a thing of the past.

Yes, it’s a big job on these cars, especially if you still have A/C and cruise control in the way (I removed mine) , and if you haven’t cleaned the Vee in a long time. Having no A/C or cruise control, I can now do all 12 plugs in about 2 hours (that counts R&R throttle pedestal)

But it’s still a job you don’t want to do again shortly, especially if you still have A/C and cruise control to contend with. So it opens up the door to a lot of other things you should do while in there.

  • Since you will have the entire throttle pedestal removed so you can get to the back plugs, you should inspect both oil sensors back there (one for gauge, other for low pressure light). They are known to leak. If they are original, I would just replace them. They aren’t too expensive. I inspected mine, they were original but not leaking. 6 months later, they started leaking. So I had to remove throttle pedestal again. A lot of times, they will barely leak, and it’s hard to see. It will leak down the back of the engine, and make it look like a RMS leak.

  • The other thing I did while I had all 12 plugs out, is a compression test. Even if the car is running great, it’s good to know condition.

  • Unless you’ve replaced your spark plug wires in the last 10 years, I would replace them. Look thru archives about all the possibilities.

  • Now is an easy time to replace the vacuum hose to the distributor vacuum advance. I’ve slowly replaced all my vacuum hoses with silicone.

I was about to ask about plug wires. I didn’t order any new ones . My old ones were changed 14 years ago when I got the car. I’ve only put 14000 km on the car but for the price of them I should order a new set.
Also do you smear dielectric grease on the wire boots.

As a foot note I can’t even think of neat way to route these wires. Probably just try and get them off the valley floor I suppose.

Ha, you’re opening up a can of worms! LOL

Original wires are 7mm. Many forum members including myself upgrade to 8mm. No idea if really needed. IMO, the only reason to go to 8mm is that they last longer. No difference in performance.

Many here swear by the blue Magnacor wires. I tried a set. They are conveniently numbered. They are high quality. But they are EXPENSIVE, and it will take a few weeks to get (i think they’re made to order for our V12). IMO, they are overrated for the price. I actually had one break on me. Could have been my fault, though.

I have since tried ACDelco 8mm. They seem to be great, and are not too expensive. Only issue is trying to figure out which wire goes where. I ended up buying two boxes so i could be more creative, still cheaper than one set of magnecors!

If you are ok with 7mm, i think oem are numbered, making it easy. And should be good quality.

FYI, the blue 8mm Magnecor wires are part 1007. About $230.
The black ACDelco8mm are part 901D. About $45.

And yes, def use a bit of dielectric grease, especially on spark plug boots. Will make clicking on/off much easier.