Hi everyone,
I own a 1985 TWR modified XJ-SC. I've had the car for a year and she's had a full service, replaced alternator, replaced harmonic balancer, replaced incorrect radiator caps and some other work.
She started running on 11 cylinders, so I am going to change plugs, distributor cap, HT leads, etc, before then doing the fuel rail and replacing the rubber fuel pipes.
My question for the group is that the TWR JaguarSport sticker in the engine bay suggests replacing with NGK B6EFS or BR7EFS.
The first plug I was able to remove from the car was a NGK BP6EFS. (I will get to the others next weekend ;-) )
I note that @Grant Francis recommends BPR6EF.
What plugs are others using these days and what are best for a weekender that does club runs, etc, but not many miles per year?
Thank you.


TWR JaguarSport recommended Spark Plugs

 

BP6EF IF you can find them. The "P" puts the spark out IN the bang juice, and makes for easier starting and better cruising etc etc.

The "R" is for Resistor, our Lucas system is not a fan of the "R", but I believe NGK only make :R: spec now, so New Old Stock is all you got left.

The system will work with the "R", its just not my preferred if I can avoid it.

 

I have always used NGK BR7EFS and all good.

 

If you are only running on 11 cylinders my first thought would be a malfunctioning/stuck injector.

Highly recommend 8mm plug wires as well. 7mm isn't quite enough insulation.

 

I'm using NGK BR7EF in my XJS V12

That at the time were really hard to get hold of, although I eventually managed to find some on ebay and it only took me 3 days to Change them!

NGK BR7 EF Spark Plugs for my XJS V12

Changing the Spark Plugs was a 'Nightmare!'

Changing the Spark Plugs on my V12 was the Job from Hell dropping the Cage was far easier

 

Hi everyone,
Thanks for all of the help. I found some NGK BP6EFS plugs locally at a very reasonable price. These are the same as the plugs I'm removing. Those have been in the car since 2018 and only 4,000 miles ago.
I also appreciate the recommendations on HT leads replacement. I will replace those and get a spare distributor cap and rotor as well. Oh, and oil under the rotor if it has seized.
A task for the next weekend or two. ;-)
Cheers, Adam

 

Oil under the rotor if it hasn’t seized. If it has seized you’ll need to free it up first.

 

And if the rotor is stiff and will not come off, ROCK it , with a hand each end rather than just pulling it off, or the mechanism below can be broken.

 

Hi brains-trust,
About to start the replacement of the plugs as all of the parts have now turned up (plugs, HT leads, distributor cap, rotor) and I have three further questions, please:
1) Why would TWR Sport specify 0.022 inch spark plug gap, where everywhere I read the recommendation is 0.025 inch gap? Is there any real impact there?
2) If I use a small amount of anti-seize on each replacement spark plug, (for easier removal next time) does that change the suggested torque for each plug?
3) And what is the recommended torque for each spark plug, please?
Appreciate any feedback.
Thanks,
Adam

 

1) Did TWR do any changes to the compression ratio when they tuned it? They probably had a reason for that recommendation, so that's what I'd go with on this car. .025" is the factory setting.
2) Anti-seize wants a lower torque spec technically, but probably not enough to matter. Especially when...
3) Snug.

I couldn't find torque specs for the sparkplugs in the ROM.

 

Hi Gareth,
Thanks for the prompt reply. She is still a 5.3L, and no changes to compression as far as I am aware, but larger throttle bodies and a freer-flowing exhaust (I believe), should should breath a little better, although the TWR branded intake trumpets look very similar to the stock ones (I need to measure their opening compared to a standard V12 one day).
And thanks for trying to find the torque value. I'm sure I read it in one of the forums, but I couldn't find it. A bit like looking for the 10mm spanner! ;-)
regards,
Adam

 

Mine had the big discs, even the PreHE.

XJ40 (3.6) throttle bodies were give away back in those days. A mate wiith a lathe, and a brain, job done.

Cold air intakes, Grant's design.
NO emission junk
NO over run valves.
NO AAV
NO Balance pipe.
NO RH FPR

Timed by Drive timing, a 1960's knowledge us old people understand.

Aussie market, so 12.5:1 comp.
I used the "P" sparkers set at 0.025" I seriously doubt -003 will make any difference, except at Bathurst, MAYBE. Look at any engine, when the ring is being rung out of it, the gaps are smaller, been that way as long as I remember.

I NEVER tracked any of them, as they were all Daily Drivers, but when I pull out to overtake a Road Train, I want it to Boogie, NOT think about it.

My dizzy PDF and some others attached for shade tree reading.

 

1- Does not matter, MORE than 25 thou is bad.
2- Anti seize VERY important
3- Place a bit of hose on the end of the plug and use the hose to turn the plug. Start them VERY carefully so as not to cross thread the almuminium. When finger tight, put on the socket and turn 5 minutes on the clockface (ie assume socket is at 12, turn to 5 past). NO tighter.

Blow out plug wells with compressed air BEFORE removing the plugs. Remove dizzy cap before doing 4 and 5 as it also makes it easier. As does a high quality 3/8ths drive universal joint socket driver.
Undoing plugs that have not been changed for years can be hard too. ALign the socket and extension straight and if the ratchet will not lmove the plug, place a bit of pipe over the ratchet handle and turn with all your might! There will be a CRACK sound and the plug will come free!

 

Thanks everyone, for your suggestions, attachment documents, and advise.
I'm doing a bit of extra maintenance as I bit the bullet and ordered the Mr Injector set to redo the injector rail hoses as well as the plugs, disti cap, rotor, HT leads, etc, that I previously procured.
Sort of a late (new to me) maintenance program that @Grant Francis suggests on purchase. (She had her first professional service when I purchased her almost 12 months ago), but I now want to get my hands a bit dirty and learn more about these great engines and my car. Also following @Adam Clementson Living with a Classic YouTube videos as well. They're terrific. He makes the work look so easy and explains tasks so well.
Got the fuel rail off today. That's a bit of work! I was taking pics of everything, making notes on how things go back together, etc.
It also obviously improves the access to all of the spark plugs, so I will continue that work tomorrow.
I really appreciate the advise offered on this forum. Thank you all.
Regards,
Adam

 

Hey team,
Update for today on clearing the "V" to get the spark plugs out. I noticed that access to 5A and 5B was blocked by the throttle pedestal. OK, so further reading and YouTubes and there are different comments on how easy or difficult this is to remove. As per the pic below, my main coil is bolted to the front of the throttle pedestal. This hampered access to the front two base bolts holding the pedestal to the engine. First off with the coil and then slightly more room to get to the base bolts of the throttle pedestal.
Ended up needing to use a Stubby spanner (7/16) and regular 7/16 spanner, and for one bolt I was able to get a standard 7/16 socket onto it with universal joint. For 4 bolts it was a bit of a job.
Work will continue tomorrow!

 

Hi everyone, I got a couple of hours to work on the car this afternoon.
At this stage, I have cleaned up the rear 1/2 of the "V" with a mild degreaser, cleaned up the throttle pedestal and main coil while I had it out of the car.
I was now able to change the rear six spark plugs with brand new NGK BP6EFS (which are the same as the ones being removed). Being a TWR modified car, it has an engine plaque that states the plug gap should be 0.022" so I have gone with that. I have also fitted new HT leads to the plugs, ready to connect to the new distributor cap, once that goes back on. Huge WIN also, the distributor rotor still has the "springy" movement and I was able to remove the old rotor relatively easily with a wiggle and gentle lifting pressure. I will apply a couple of drops of oil down the distributor shaft to lubricate it.
A couple of pics of the work so far. You can see the difference in cleanliness between the rear and front of the "V". Also, I label EVERYTHING that is removed and take pics of everything I do. That's ay so may blue tape labels.
Feedback welcome. Putting the throttle pedestal back on with the main coil was just as difficult as the removal process. Just a very tight space to work in.

Label EVERYTHING!

Throttle pedestal and main coil cleaned up.

New spark plugs ready to go in.