19-02-2021, 11:13 AM
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.
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.