Coil HT Lead Removal MKV Distributor Cap

(Timothy M Fox) #1

Hello all,

Okay I’ll admit to being stumped as to how to remove the HT coil lead from the side entry distributor cap on my MKV? Removing the HT plug leads was obviously the screws in the cap, which I’ve done, but the cap to ignition coil??

Once I know that will be it!



(Graham Jordan) #2

I’m not at home to check my spare cap but there is a screw there somewhere
See if the screw is under the carbon contact in the centre inside of the cap. I just can’t remember offhand

(Peter Scott) #3

Yes, you need to pull the carbon contact out to access the cable screw.
It helps to rotate the carbon so that the spring contracts in diameter. Sorry, I can’t remember which way its wound.


(Timothy M Fox) #4

Thanks Peter.

I guess I’ll try counter-clockwise unless someone else knows for certain.

All the best,


(Timothy M Fox) #5


Counter-clockwise and very gently pull then out it came revealing the screw.

Many thanks,


(Timothy M Fox) #6

Now to polish the cap.

Brasso is fantastic for polishing bakelite.


(Roger McWilliams) #7

Once carbon contact and spring are removed from distributor cap interior center, remove that hidden screw all the way out, not just freeing the wire. These screws can corrode over time and should be cleaned, or at least inspected, to provide good electrical connection. When corroded, the screw can provide decent spark path when cold which then becomes ineffective when the distributor is hot. Intermittent stumbling and failure to restart while hot can occur with corroded screws in the distributor cap.

Also recommended is to inspect the rest of the distributor cap. The cap in the picture looks like a good cap worth continuing to use if in good condition overall, there are poor reproductions subject to tracking failures when hot.

(Timothy M Fox) #8

Hi Rob,

I’m very fortunate that it’s a great original cap in near perfect condition. No corrosion either. I’ll lightly grease the screws with Copaslip.

Thanks again,


(Ed Nantes) #9

I would suggest a. Set of Hyperlon leads from Performance Ignition in. Nor cal Rd Nunawading they would need to fit them to your cap.

(Timothy M Fox) #10

Why did Jaguar have number one cylinder at the rear of the block unlike most cars which have number one at the front?:thinking:



(Timothy M Fox) #11

Hi Ed,

I replaced the leads myself with 7mm black cotton braided copper core from the UK (The Green Spark Plug Co.) with the original brass spark plug ends and brass knurled nuts on the new plugs! Looks great and runs beautifully. Feeling a bit content with myself (ever so humbly) at present, having done it successfully.


(Peter Scott) #12

I have no idea, but how you identify them really doesn’t matter so long as you obey the firing order and you wire the them up so that the leads exit the cap at a sensible angle. You only need to decide in which direction you want them point then after setting any cylinder to tdc with both valves closed connect that cylinder’s plug to the cap contact that the rotor arm is pointing to and after that follow the firing order. You can call the third cylinder from the front number one if you like. It makes no difference.


(Rob Reilly) #13

Because Standard did? As you may already know, the side valve and push rod engines were bought from Standard before the war, and the tooling to make the six cylinder engines was purchased from Standard in 1945.

Why did Standard do it that way? My theory is that when the crankshaft is put in a lathe to cut the journals, they start from the rear flywheel face and work forwards, so they numbered the journals starting from the rear. Either that or the bearing caps in the block were bored from the rear forwards and numbered accordingly.

One might say they were non-standard? :laughing:

(Paul Wigton) #14

I believe it harkens back to aero engines, where the prop end was the flywheel end.

(Timothy M Fox) #15

Hi Paul,

That makes sense to me, thank you.

“Tally Ho!”



(Timothy M Fox) #16

Hello Peter,

Thank you for your thoughts. I understand the principle of any cylinder potentially being number one I was just interested as to why Jaguar decided number one was the rear cylinder and not the front?

I laughed at Rob’s suggestion that Jaguar used the “non-standard, Standard engine!”. I think that JCC’s suggestion that Jaguar followed the pattern of the British Aero Industry of the flywheel being at the 'prop-end’ making number one cylinder at the rear of the RR Merlin the most probably improbable!!



(Peter Scott) #17

Hi Tim,

I guess that “back when” there just wasn’t a standardised convention for the numbering. I think it really is fairly meaningless except where you are reassembling crank bearings or pistons etc.


(peter balls) #18

I have a previous post on this subject.
Jaguar workshop manuals state that “all dimensions” left / right etc,
“are to be viewed from the drivers seat”, No 1( rear cylinder) being first in line to that position. The XK engine cam timing is set to fire on number 6 therefore the ign timing should be viewed as 624153
not the oft stated 153624 resulting with ign 180 degrees out.
Peter B.

(Rob Reilly) #19

I have not found any evidence that Standard Motor Co. was ever involved with making airplane engines, although they did build Royal Aircraft Factory and Sopwith planes under license during WW1 using other people’s engines, Hispano-Suiza and RAF mostly. They were building six cylinder car engines as early as 1905.

If the draftsmen at Standard were anything like those at my lab, the guy who first drew the crankshaft in 1905 would have put the flywheel flange on the left side of his paper and dimensioned all the crank pins from there, numbering them 1-6 left to right. The machinists, assemblers and service people would naturally follow that lead.

Jaguar did not continue the back-to-front numbering with the V12; cylinders 1A and 1B are in the front.

(Timothy M Fox) #20

Follow up question.

In the photo from the Service Manual it shows the HT leads passing through a metal bracket with a rubber grommet inside it. I bought two of each from Barretts just in case there were two, one on each side of the Block tp keep them away from the heat of the block. Are there two and do they just bolt onto the Bell Housing / Engine Block bolts? The set of leads fitted to the car when I bought it were just lying on the Bell Housing cover!