Silicone Ignition Leads

[ALAN COCHRANE]

Hi Everyone

Has anyone experience of using silicone ignition leads. I have a set of period correct Champion spark plug caps which I'd like to fit along with a full set of lead separators. I bought a part drum of Durite 7mm suppressed silicone cable a while ago from our favourite auction site.
The existing copper leads aren't long enough to fit all the spacers so I'd like to change them.
The existing caps are suppressed while the period Champions are not, hence the idea of using silicone leads. More to the point how do you terminate them in the cap and in the screw in distributor cap connectors?
All advice gratefully received as usual.

Alan

[cactusman]

Afraid my advice would be "don't". The old champion plug tops are intended to screw into the end of the ht lead as you say. The copper core of an original lead is fine to have a screw thread fitted. Silicone leads have carbon cores. I fitted a set to my mg years back. They were fine for a few months but eventually the car developed a mis fire that was eventually traced to damage to the carbon core caused by the screw thread. You will find too that the acorn threaded caps and brass washers at the cap end will also be problematic. The dizzy cap and plug tops need copper cable....stick with it. It is readily available and not costly.

[Heuer]

SNGB sell a complete copper core HT lead set, conduit, plastic sleeve and Champion Bow Tie plug caps for £55. Silicone leads are pretty pointless on the E-Type unless you have sophisticated electronics that need high levels of suppression. The D-Type lead separator looks cool but is, again , of little use on a road car.

Silicone leads require moulded on plug caps and dizzy connectors, you can't use the screw in type. Stick to copper core leads unless you have a sophisticated ECU and even then I doubt you will see a difference.

[malcolm]

Just for interest, and my car may be a one-off in this respect, I fitted a new powerspark unit to my Dizzy, along with new dizzy cap, leads, coil, everything. Ran beautifully until I hit 4200 rpm when I got a terrible misfire. Tried new coils, no difference. Spoke to the suppliers of powerspark unit who said it would be interference from my (new) copper HT leads. they supplied a full set of silicone leads including king lead with moulded plug caps and ends to suit my dizzy and coil for £39. Having tried (and swopped) everything else, this solved my problem instantly.

[Heuer]

As I said, if you have electronics in the mix there can be problems although they are usually solved by the use of resistor 'R' spark plugs as I found out with the EDIS/Megajolt install. It already used silicone leads but the only way to cure a misfire was R plugs. I would always suggest changing the plugs before messing with the HT leads.

[Hugo]

I remember way back in the last century when these things first came out. Being used to seeing proper copper plug leads, the appearance of leads with string instead of metal running through them caused some consternation at the garage where I worked. These were on a Ford Anglia or Cortina or something (definitely a Ford - we were a BMC garage). We had no end of trouble with these 'string' leads leaking in the damp weather.

[paydase]

Troubling indeed....
Then better stick to the good ole pure copper leads and screwed plug tops and cap ends, more resilient to abuse and humidity and easily fixable up to some point when issues arise!

[Heuer]

Champion bow tie plug caps are suppressed with a 5k resistor so there should be no need for suppressed cables or suppressed plugs. Unfortunately various bits of electronics react differently either by design or build quality. A case of trying everything, one step at a time.

[malcolm]

Interestingly, I never had the problem of misfiring with the old copper leads I had using the powerspark module. But the new copper leads I fitted from SNG were a fair bit thinner than the originals, so perhaps the new ones provided less screening?

[ALAN COCHRANE]

Copper leads it is then. Anyone want a part drum of silicone cable, going cheap?
I'd still like to use the Champion "oval" plug leads which are correct for my 1961 E-Type. Any ideas where or even if I can source a set of 5k resistors for them, or should I just go down the unsuppressed route?
I only have the Petronix electronic ignition fitted, everything else is standard. Even the modern Sony head unit for the radio is stashed away in the boot so hopefully would not be effected by any interference.

David

I've been on the Jag Lover's Forum and came across the discussion you were involved in concerning this very subject:-

https://forums.jag-lovers.com/t/spark-p ... /351983/37

Am I right in assuming you have unsuppressed oval caps mated with suppressed carbon leads on your FHC?

Alan

[Heuer]

Alan

I am using copper leads, Champion oval caps and the impossible to find 5k plug in resistors as per original Factory when a radio is fitted. Dizzy is stock, no electronics.

If you want to use the oval caps and copper cable I suggest you fit resistor spark plugs to avoid interference. These have a 5k resistor built into them and have a 'R' in the part number e.g. BPRS7. Standard plugs do not have the R designation. Available from any motor factor or even Amazon for about £3 each.

So the options were (in date order):
1. Copper HT leads, no suppression
2. Copper leads with plug in 5k resistors
3. Copper leads with BPRS resistor plugs containing the 5k resistor
4. Suppressed silicone leads ( never fitted to the E Type as they are a later development)

All do the same thing, just try and avoid doing two or more at once as you will begin to reduce the spark

[johnetype]

David,

Whilst true in date order, as your 3.8 Factory Fit thread points out Option 1 is not legal and a compromise of Option 1 with Champion WCX600 caps whilst not so strictly original would be better. The use of plugs/leads with resistors in them deliver a better spark to the engine as well as reducing interference.

Option 4 implemented using Jaguar OE silicone leads as used on the Series 3 XJ6 I believe is the best option for reliability and performance just not originality.

[Heuer]

You just need 5k suppression somewhere in the spark system whether it be leads, caps or plugs. So using the unsuppressed oval caps with copper HT leads and R plugs is the best combination for both originality and practicality. I don't think the silicone leads offer any gains in reliability or performance, they just limit you to using the supplied moulded plug caps rather than the Champion Bakelite ones. In fact they do not prevent disruptuption of EDIS/Megajolt and you have to use resistor plugs. So misfires when using electronic ignition may not be cured by just fitting silicone leads.

[Series1 Stu]

We used to use these, back in the day.

http://www.gsparkplug.com/1x-inline-sup ... 8-EALw_wcB

One in the king lead first and if that doesn't work then add them to the plug leads.

We also used to festoon the engine bay with supression capacitors on wiper motors and heater fan motors etc.

Regards