Whilst i was getting my carbs jetted up, Andy Bates advised me to ditch my Silicon HT leads and replace with the traditional 8mm Copper core style.

I've not got around to this yet, but just curious what some of you other folk run with BEC's.

My Indy doesn't feel or sound as smooth as it should and im hoping this is down to the (old looking) Silicon leads i have.

However, the plugs looked good when i whipped them out..


[Edited on 25/3/17 by Banana]

i believe the silicone ones are of a much higher resistance, thus eliminating electromagnetic fields which could interfere with sensor signals..

when you speak of carbs i'm assuming there's not much electronics on the car so i dont think you would have any problems with that.

maybe keeping the silicone ones and upgrading your coil would be a better idea? (if the coil isn't upgraded yet...)

correct me if i'm wrong

Carbon and silicone plug leads are suppressed leads they produce less electromagnetic interference.
The designed in ressistance in the leads has zero effect on the required ignition voltage and almost zero effect on spark energy.
The reason for this is the the few k Ohms resistance of the plug lead is nothing compared to resistance of spark plug gap.
This image shows what the spark plug voltage looks like when the plug is fired.
Peak voltage at the start of the spark is anywhere between 15 and 45 kV




The resistance of carbon fibre cables can be measured end to end with an ordinary DVOM and should be 10kOhm to 20kOhm per meter
The ressistance of silicone cables is typically 2.2kOhms to 8kOhms per meter.
A typical car manufacturer's OEM plug lead will have an end to resistance of 6 to 18kOhms depending on length anything greater than that points to break in the conductor.

The other test you can do is test the insulation only basic tools. I usually use an ordinary tungsten bulb test light connected to the cylinder block as an ground but a piece of wire connected to ground works just as well. This test works best in subdued light with the engine at idle speed just run the tip of the test lamp (or wire) along the plug lead looking for a spark leaping to ground. Then you can repeat the test after giving the leads a spray with water.


[Edited on 26/3/17 by britishtrident]

[Edited on 26/3/17 by britishtrident]

[Edited on 26/3/17 by britishtrident]

Thanks for the detailed reply!

So if i read that right, it makes naff all difference.

Regardless, both type are still a serviceable part which degrades over time.