Ignition Leads

[alistair260661]

ignition leads resistance?



I bought a new set from a well known supplier and discovered that the resistance in all of the leads is much less than the originals leads I was replacing. The strange thing is that the new leads produced a very very weak spark at the (new) plugs. So bad in fact that the car didn't run worth a damn.

I put the old ones back on and it runs well - can anyone explain why this might be?

Oh - I still have a tiny hesitation/miss from time to time under load...... any ideas? I've sent the "new" leads back for replacement with a silicone set... hopefully this might cure it

[V8 Rumbler]

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Hi Alistair--which leads did you buy and from whom---this info will stop someone else going through the hassle that you have. Many components from some supplier are 'not fit for purpose':X

Have a look at the LD parts web site---Peter will only sell something that he knows works.

Darren




alistair260661 wrote:

ignition leads resistance?



I bought a new set from a well known supplier and discovered that the resistance in all of the leads is much less than the originals leads I was replacing. The strange thing is that the new leads produced a very very weak spark at the (new) plugs. So bad in fact that the car didn't run worth a damn.

I put the old ones back on and it runs well - can anyone explain why this might be?

Oh - I still have a tiny hesitation/miss from time to time under load...... any ideas? I've sent the "new" leads back for replacement with a silicone set... hopefully this might cure it

[Stagdad]

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I've got a set of Moroso leads to fit,quite pricy so it will be interesting to see if they along with a flame thrower coil make any difference.Ill run it as standard first so i can compare.

Cheers Steve

[mjheathcote]

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Can recommend a set of Magnacor leads

[Peter Hills]

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Resistive leads - resistor plugs?:?

[GDPR]

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Resistor leads and resistor plugs together shouldn't make any difference to running unless you have low HT output from the coil or a dodgy rotor arm.

In my experience.......

[singapore stag]

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mjheathcote wrote:

Can recommend a set of Magnacor leads

Hi, Which colour Magnacor leads did you get?. Are the KV85 (red leads) ok to use.

Cheers, Sukh.

[V8 Rumbler]

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singapore stag wrote:

mjheathcote wrote:

Can recommend a set of Magnacor leads

Hi, Which colour Magnacor leads did you get?. Are the KV85 (red leads) ok to use.

Cheers, Sukh.

they would be fine to use but designed for race engines & IMHO unnecessary for a Stag.
I use MAGNACOR 8.0 CABLE (blue ones) on my disco V8 - she is running LPG so the ignition needs to be spot on. The leads have been on there for nearly 3 years and re still performing as they should

Darren

[singapore stag]

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Thanks Darren.

[mjheathcote]

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singapore stag wrote:

mjheathcote wrote:

Can recommend a set of Magnacor leads

Hi, Which colour Magnacor leads did you get?. Are the KV85 (red leads) ok to use.

Cheers, Sukh.

The 8mm blue ones.

I had Magnacor make up my leads too, to my length and end boot style

Main reason was that I wanted all my boots at mydistributor to be 90's, to aid clearance of my kickdown cable and throttle cable, having a Holley, and a neater appearance.

[Stagdad]

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mjheathcote wrote:

singapore stag wrote:

mjheathcote wrote:

Can recommend a set of Magnacor leads

Hi, Which colour Magnacor leads did you get?. Are the KV85 (red leads) ok to use.

Cheers, Sukh.

The 8mm blue ones.


Main reason was that I wanted all my boots at mydistributor to be 90's, to aid clearance of my kickdown cable and throttle cable, having a Holley, and a neater appearance.

Same reason i got the Moroso leads and crimp tool ,they comewith the 135deg plug endmade up and with both types of boot for the other endso you can get them neat with no excess cable.

Cheers Steve

[alistair260661]

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going back to my original post...................... does anyone understand why I've had this issue - low resistance leads providing poor spark.................... and as to the remaining slight hesitation/miss what might be causing it............?

[GDPR]

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The theory goes that the higher the resistance the higher the generated voltage in the coil has to go before the spark can jump the gap - same effect as opening the plug gaps.

In days of old, they used copper leads on magnetos and coils as they could only manage about 12kv - but that didn't really matter as the compression pressures were pretty low but they could ill afford to waste any voltage.

Then as coils improved we had copper leads with suppressor caps that screwed on. That increased the resistance and therefore the firing voltage.

Some high performance cars then starting specifying resistor spark plugs to force the voltage higher and therefore hotter.

That's why resistive leads are so important.

[alistair260661]

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thanks - simple really!

[V8 Rumbler]

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Hi Russ
So if we tested our leads what figures would we be looking for?
Darren


kryten wrote:

The theory goes that the higher the resistance the higher the generated voltage in the coil has to go before the spark can jump the gap - same effect as opening the plug gaps.

In days of old, they used copper leads on magnetos and coils as they could only manage about 12kv - but that didn't really matter as the compression pressures were pretty low but they could ill afford to waste any voltage.

Then as coils improved we had copper leads with suppressor caps that screwed on. That increased the resistance and therefore the firing voltage.

Some high performance cars then starting specifying resistor spark plugs to force the voltage higher and therefore hotter.

That's why resistive leads are so important.