Ignition Leads

[on2wheels]

Hi,
Originality or practicality, that is the question?
Do you experienced e-type owners have your leads gathered together in a cardboard tube or have you separated them?
There is also a clever plastic tube at the front of the engine. See photograph.

If you stick with the cardboard tube how does one clean the leads or carry out any maintenance?
The tube appears to be riveted along its edge. Is there any way of opening it?
Car runs ok, but not able to get it to 150mph yet. :o

[Heuer]

Depends on what you want from the car. If you are not bothered with originality then the Moroso leads and D-Type style paxolin separator work superbly and look 'period'. Rob Beere supplies: http://www.rob-beere-racing.co.uk/ignition.html#leadsep

[MarkE]

I had the original setup, with fine cardboard tube and bow-tie Champion spark plug caps, and it looked just right. I put a photo up here and David said....you'll want to change those, they give problems.

Pah, I thought. How can anything that looks so good give problems?



The car was taken up to CMC to be trimmed and fettled, and on lifting the bonnet, Andrew Turvey said....you'll want to change those.. they give problems.

They were of course right....the car lasted 20 miles before it started to misfire. So now it has the seperator thingee and modern caps properly engineered and not knocked out in Vietnam for the cheapest possible price.



I know I keep on saying it, but why can't anybody make repro stuff properly??!!

When the cars were made they used the cardboard tube with the leads bundled inside and the Champion plug caps and they worked for years and years without problems.

[ChrisC]

How are the leads fed through the paxolin strip? Does it separate?

[PeterCrespin]

Leads are fed through the Bakelite strip then caps fitted.

In fairness, part of the reason these components give trouble today but didn't back in the day is the ignition systems today are rarely OEM spec.

People running points and an old tech coil should be fine. People running electronic ignition and powerful coils are creating fatter sparks that will burn rotors faster and crossfire the leads more than in days of yore.

[ChrisC]

but you cant take the caps off silicon leads surely....

[Heuer]

The Moroso leads have moulded on caps so you need to buy the complete lead/separator set from Rob Beere.

[GSR 54D]

Hi Mark;
Are you using an electronic distributor with those news silicon leads?

Last Thursday my car broke down on the road for the first time since I had it, hard acceleration through 3500rpm and suddenly massive back fire and loss of power initially thought that was the end of the engine. However limped off road, got help, loosened distributor (which appeared solid as a rock) turned it a few degrees, wiggled all leads removed and reinserted vacuum pipe and off I went again 5 miles home without a splutter.

Now initial thought was the distributor turned slightly under hard acceleration, however not convinced due to distributor being firmly in place, now wondering whether to change ht leads.

I currently have a 123 distributor with "home made" silicon leads in the original card board trunking. Am thinking of going the high price Rob Berre route with non-standard separator appearance (hard to swallow!) and proper lead connections.

2 questions here please:
Firstly; when undoing the 2 engine head nuts to remove the card board trunking is there any chance of doing damage? ie. stud shearing etc.
Secondly; if one has these nice moroso 8mm silicon leads would they be fine if I revert to the original point system Lucas distributor?

John H.

[ChrisC]

I am not sure but I think making your own leads is the cause of the problem. I may be completely wrong but I thought they came in a number of premade lengths with the end caps sealed on.

I am currently looking around for the D-type separator strip that is split. I have seen them so I know they exist but i dont know who sells them (yet)

[GSR 54D]

Hi Chris

No doubt my home made ones are not perfect however regarding lengths I wanted flexibility and so bought one length of about 5 metres, loose connections and used a proper ignition lead crimping tool for the job (had no problem for 18 months).

Here is a link to a black separator however it doesn't come a apart: http://www.coolcatcorp.com/Merchant5/me ... ry_Code=IC

Interestingly Coolcat does extended leads for my cardboard trunking but obviously this still means the leads are bunched up and not separated.

John H.

[MarkE]

John, I'm very old fashioned and use the original distributor, I prefer the old coil / points / condenser approach, if the components are to original spec, as they are very reliable, but simple to fix if they do go wrong.

I've had problems with more modern ignition systems on old cars, probably down to lack of use and / or developing poor earths, but when they go I'm at a loss to know what to do, other than rip it all out and start again!

Strange though that I've never had a problem with the old Opus system on the V12, and it's original to the car. Everybody says to change that for a modern replacement, and one day, with the bonnet up on the side of the road, I expect i will wish I'd listened!

[PeterCrespin]

I am not sure but I think making your own leads is the cause of the problem.

Without seeing the leads, who knows what the problem was, but the car needs to be timed correctly if the distributor has been turned arbitrarily at the side of the road. Since the thing was solid I'm not clear why anyone would think random turning would do anything other than risk adding a new issue?

Making your own leads is not rocket science. A decent spark will jump a quarter of an inch / 6mm no probs, so since even the most cack-handed assembly job is going to do far better than that, you'd be hard put to screw it up. Yes, there's always the exception to every rule...!

I made mine up in original black plastic-covered solid wire material and ran them all the way under the inlet manifold and into the valley from the back, like the XK120. I therefore have no leads coming up over the cam covers or timing chest and have the very 'clean' look Lyons and Heynes wanted in the first place. Dead easy with screw-on bow-tie caps.

[Heuer]

Making your own leads is not rocket science.

No it is not, it is 'rocket engineering' not the oft quoted 'science' unless of course you are in a room of said engineers and really want to annoy them, in which case fair enough.

[PeterCrespin]

No it is not, it is 'rocket engineering' not the oft quoted 'science' unless of course you are in a room of said engineers and really want to annoy them, in which case fair enough.

Dunno. I always heard the saying was 'rocket science'. Googling 'it's not rocket engineering' gets you 9 of 10 hits being 'rocket science' (and the outlier isn't on topic anyhow...) :-)

http://www.lmgtfy.com/?q=It%27s+not+rocket+engineering

Now then, Grasshopper, let us discuss the comparative dielectric constants of rubber, plastic, silicone and mixed-media cable sheaths and the influence of low resistance/high inductance designs on the cross-firing potential of high tension pulsatile energies passing along specialised ignition conductors...

That ought to send everyone to sleep :-)

[Heuer]

Thank you most kindly Master Po! However I can't see how you can 'science' a rocket but I reckon you can engineer one. I wonder whether William "Bill" Heynes, ably assisted by Walter "Wally" Hassan regarded themselves as designers, scientists or engineers when they 'did' the XK engine?

Anyway it is always good fun to correct people who say "It's not rocket science" with this jibe; kinda takes the wind out of their sails

[PeterCrespin]

Anyway it is always good fun to correct people who say "It's not rocket science" with this jibe; kinda takes the wind out of their sails

Actually, we're both wrong. Here is the truth about Rocket Science.

http://tinyurl.com/6hsx57r

Pete

[GSR 54D]

Thanks for replies!

Spent a morning re-checking timing with strobe and all appears ok. Also changed spark plug lead caps from "champion bow-ties" to insulated rubber straight caps using proper crimping tool now nice and snug. No problems since however yet to push hard again.

Was wondering; if accelerating hard when engine at its normal (hot) running temperature and a lead/cap failed would I get a lot of back-firing rather than miss-firing?

John H.

[pmansson]

is the early 120 layout, whereby the lead wires entered the cyl head valley from the rear. That way the front of the XK engine is kept clear.
Calls for a distributor cap with sideways mounted leads (? la Ferrari of the 50s and 60s) rather than upwards. The latter could be used but is less tidy.

[PeterCrespin]

Yes, I looked into that but sadly the side-exit types are clip-on caps whereas my XJ6 electronic dizzy uses a screw-on cap.

I made sure to hold the leads up by supporting them on their run under the manifold so they didn't dangle or sag. The first turn backwards from the upright dizzy cap terminals to under the thermostat housing and manifold is somewhat tight, but not extreme in any sense. You just have to factor it in when cutting your leads to length.

The other advantage is that athough I put white number collars on each end of each lead, the leads lying in the valley can really only go back on one way due to their very obvious length differences. So you can rip them all off with gay abandon when doing plug chops etc. and they only go back one way. Same goes for the cardboard tube of course.

Mainly though, I just like the tidy 'pure metal' look of not having any wires draped over the front or side of the cylinder head. The only way I'll do so again is because on the D-type under construction it's period-correct to have the separator over the cam box.