Accu spark

[Zetomagneto]

Small self tapper through the washer and into the lead. I personally don’t like carbon leads

[Peter Johnson]

They came with a little push in stake in my case. The stake was u shaped with barbed edges and pushed between the core and the outer insulation.

[Steve kay]

Ah, you’ll not be fastening those cable ends in Whitby in November, then. I was informed that It was my turn to come up with such a silly comment. Shall we “ count” the number of people who want to say that? It is not really a relevant fang sorry, thing, to mention. I’d better throw a cloak over the whole matter, and scurry through the heavy but warm rain to the workshop.

[Paul N-M]

Hi Jacob,
Unless you MUST fit carbon ones why not cut your losses and make up some copper core ones? In my experience they are by far the best when using conventional ignition and easy to make up. If you have an electronic unit then look to protect it. Magnacor comes to mind but there are other suppliers. They will make up leads for you which avoid the type of issues you are experiencing at a very reasonable cost.

[John Cornforth]

Hi

In case anyone's interested, there are basically four generations of HT leads (dates very approximate):

up to 1935:             Copper Core

1935 to 1960:         Copper core with resistor suppressors (typically 5000 ohms) at the plug caps.  Suppression a legal requirement (not retrospective) from 1953.

1960 to 1980:         Carbon core resistive, typically 5000 ohms per lead

1980 onwards:        Inductive, the core is a fine coil of stainless wire wound over flexible ferrite.  Typically 500 ohms per lead

Of these, I have found that the copper core and inductive types last indefinitely, whereas the carbon core types break down and end up with lots of internal air gaps.  They are also a pig to connect to reliably with home tools, normally they come with factory fitted crimps.

Suppression of radio frequency energy was initially to reduce interference to nearby radios and TV sets.  Once electronics made inroads into car engine management etc, it was also necessary to prevent mis-operation from picking up ignition pulses.  I imagine that Accuspark had this in mind when recommending carbon leads.

On my own Seven, I use copper core leads with separate 4700 ohm resistors between the lead ends and the plug spade connectors.  These are covered and reinforced by black heatshrink sleeving, so don't look out of place for 1936.  Before fitting them I had trouble with erratic readings on the electronic rev counter.

I'd suggest either copper leads with suppressors at the plug ends, or inductive leads.

The loss of spark energy from fitting a properly designed suppressor is negligible.

[andrew34ruby]

Interesting John, but I think BMC and others continued with copper leads into the sixties. I was lead to believe the suppression resistance was in the sprung centre contact of the distributor cap. The carbon brush.

[Ivor Hawkins]

Just my personal opinion and call me old fashioned, but every car I’ve found to have carbon leads, I’ve changed to copper for reliability after having my old Sunbeam started missing for no apparent reason...the carbon leads were at fault.

[Jacob Fowkes]

Coppers are on , engines running ! I have no idea why they supply the carbon ones! Great kit but rubbish instructions and the leads well ... they’ll look nice on the wall! . Cheers chaps for all the help

[Ivor Hawkins]

Hurrah!
As the old song goes: you can’t trust the specials like an old time copper!

[Stuart Giles]

Coppers are on , engines running ! I have no idea why they supply the carbon ones! Great kit but rubbish instructions and the leads well ... they’ll look nice on the wall! . Cheers chaps for all the help

There is some more debate on the subject of carbon leads in this thread that highlights why manufacturers of aftermarket ignition systems specify them.... https://www.austinsevenfriends.co.uk/for...p?tid=2558