Plug gaps

[jbcollier]

FYI:  Lucas Sport coils (gold) have the correct resistance and work well with a Pertronix  unit.

[EuropaTC]

(part Quote)
though I have been told that they are not compatible with my solid core ignition leads. The RF energy given off by solid core leads will apparently destroy the electronic module in time. I emailed Pertronix to query this and they confirmed, and said that even with resistor caps fitted at the plug end of the leads (which I have) they will not guarantee the reliability of the electronic module. However many people online say they have no issues with this set up, so it sounds like a crap shoot.

At the risk of digressing off topic, I've heard the same about copper cored leads with pretty much all of the common aftermarket electronic ignition systems and it puzzles me a lot, so if anyone is an expert on this,  shout out ! 

I can understand why copper leads with NON-resistive caps might be a problem but struggle to understand why copper leads plus 5k caps are no longer suitable.  I did buy modern leads for my first attempt with the Elan but....   AFAIK the resistance is dependent upon the length of the lead so if you cut them as short as possible you get less than the 5k of a copper lead/cap, or if you have long leads then you're putting more resistance in the circuit according to my meter.

But it's the coil doing the sparks, the CB points or Pertronix are surely just there as a switching device, so isn't more resistance a bad idea ? I ended up with the usual Lucas sports coil, copper leads & NGK caps plus carrying a spare pair of CB points/Condensor in case the internet is right and it suddenly fries itself.... 

[BDA]

This wire situation is a bit worrying! I believe I have stainless steel core HT leads and I don't have resistance plugs or any resistor in the plug connector. I haven't had any problems (yet) but I probably have less than 5000 miles (but could be marginally more) on my Pertronix. Like Brian, I'm at a loss to understand why the HT lead would be an issue for what is really a switching unit but then you don't have to get very deep into electronics before I'm at a loss to understand anything - it seems like if it would be a problem for anything, it would be for the coil. Maybe it's worth a call to Pertronix...

Edit:
I looked around and found out that Pertronix makes plug wires. I think if you call them, they'd point you to them. They make the modern size 8mm size in cool colors but they won't fit in the side wire 23D cap so you'd need to get the "stock-look" black wires. They don't make a set for the TC so I don't think you can be certain that all the wires will be long enough if you get a 4 cylinder set (and certainly don't have a set for a BDA!) so I think a 6 cylinder set like this one (https://smile.amazon.com/Pertronix-706101-Flame-Thrower-Custom-Cylinder/dp/B004OXPTC8/ref=sr_1_1?s=automotive&ie=UTF8&qid=1479855261&sr=1-1&keywords=pertronix+7mm+plug+wires) might be the best bet. Of course, they also sell their own distributors, including a 23D replacement that probably would take the 8mm wires if you need a new distributor or just have to have spark plug wires in cool colors!

Edit again:
Reading Pertronix's admonition against solid core HT leads, it appears to say that any suppression wires are appropriate. My reading is that they expect that using solid core HT leads would interfere with the electronics and functionality rather than damage them:

"You cannot use solid core (typically copper) spark plug wires with this product. Solid core wires do not suppress electro magnetic interference (EMI) which will interfere with electronics in this product. A suppression style or spiral wound spark plug wires must be used."

So it might be that if you are getting away with solid core HT leads with your Pertronix unit, you should be happy that you're apparently getting away with murder so you should just smile and continue driving.... But you apparently don't need their own wires...

[EuropaTC]

(part quote)
"You cannot use solid core (typically copper) spark plug wires with this product. Solid core wires do not suppress electro magnetic interference (EMI) which will interfere with electronics in this product. A suppression style or spiral wound spark plug wires must be used."

That was the bit I puzzled over, although I can understand how an non-suppressed lead can cause EMI because in the olden days I had a Sprite with cute little plug caps that weren't resistive and the radio was a constant crackle as soon as the engine started. ( I think it's illegal to run such a system over here now, but that could just as easily be another internet myth. )

I read it as "you need some resistance" and inferred my own dubious logic that if the radio wasn't crackling, I'd got enough there. (yes, I know, little knowledge, dangerous things....     )   Anyway that was my logic in keeping copper leads with NGK caps - the radio works.

Incidentally you hit on both of the snags I met on my trial with modern leads; the first set, despite being assured would fit a TC were way too short and needed to go back, with measurements of what would fit. They arrived and then were too big for the (new) distributor cap.  Much bodging and shaving of insulation got them in and working but I wasn't comfortable with the bodges or the plug connectors which felt flimsy compared with the NGK caps, so I went back to the old leads.....

[jbcollier]

If you compare the secondary ignition voltage traces from suppressed and unsuppressed ignition wires, you will see a huge difference in the amplitude of the ignition "after-shocks".  Remember that what happens in the secondary circuit affects the primary circuit as well.  So unsuppressed secondary circuits can create significant voltage spikes in the primary circuit.  This is what may fry an electronic module.

Many people think that resistance in the ignition secondary circuit is a bad thing.  Actually, it's not.  What fires the mixture is not the spark but the ionization of the plug gap. Using resistor plugs and wires reduces the "spark" and increases spark plug life as well as controlling RFI.  Whether the resistance in the secondary circuit is created by using resistor wire or resistor connectors does not matter.  I favour resistor connectors such as spark plug caps as they seem to last longer than resistor wire.

[BDA]

Your posts are almost always an education, John! I have another set of connectors that will fit with my BDA that may or may not be resistance connectors. I assume I can check the resistance with a multi-meter. What resistance should I be looking for?

Edit:
I should learn look before I type. It says 3k ohms on the side of the connector. I would guess that's enough. Now I just have to figure out how to connect a wire to it!

[EuropaTC]

Good post John, you're way, way ahead of me on this one but your explanation is simple so I can just about get there.  From what you're implying in the last couple of sentences it sounds like I might not need my spare CB points after all.....   

[jbcollier]

Pertronix units can die if you do not follow the instructions, or are careless.

- Make sure your coil has the recommended primary resistance.  Too low and the excess current flow will fry the module.

- Do not hook up the red and black wires backwards.  Seems pretty basic to me.  Right up there with don't put small children into blenders.  However some people struggle with this one.  Use red and black paint markers on the coil terminals and red and black heat shrink on the wires.

- Disconnect the pertronix unit if you are going to leave the ignition on for a long time.  You should also disconnect the points wire on a standard ignition in the same situation as it can fry the points as well.  I have never had a problem with this but some people say it is an issue.  Given that you can fry points as well this way, I'd call it even.

- Don't cary a spare points plate.  You would have to reset the timing if you swapped points back in.  Just carry a spare pertronix module.  Smaller to carry, quicker and simpler to change and no resetting required.

Back onto resistance in the secondary circuit:

- stock ignition? Don't use BOTH resistor plugs and regular resistor wires.  Might get to be too much for the stock system to handle at high revs.  It's ok as long as the wire resistance is below 5K ohms but above that might mean problems. 

[BDA]

Thanks for the additional info, John!

I thought I had read somewhere that earlier units were at risk if the ignition was left on for too long (don't remember the definition of "too long"), but that later ones were designed so that wasn't a problem. I know I mistakenly left my ignition on for probably five or ten minutes and it didn't seem to hurt my unit.

I just found the documentation for my Pertronix and it says:

Q: What happens when I leave the ignition switch on when the engine is not running?
A: This can cause your coil to overheat which sometimes will cause permanent damage to the coil and the Ignitor (Pertronix unit).

More evidence that I'm often luckier than I deserve and my memory is sometimes a poor source of information!

[Bainford]

Thanks for the info, John. Very helpful stuff in gaining further understanding.

- Don't cary a spare points plate.  You would have to reset the timing if you swapped points back in.  Just carry a spare pertronix module.  Smaller to carry, quicker and simpler to change and no resetting required.

Should I decide to ditch my points, which will eventually happen, this is intended my course of action. I need to identify the necessary replaceable parts, and determine cost and availability. I haven't looked into it yet but I assume the procedure is straightforward.

[BDA]

Pertronix sells service parts so you can keep a spare "module". Replacing it should not affect your timing (but I'd still check it after I installed it). You can use Google to find the best deals. Here is the Pertronix ignition catalog:
http://www.pertronix.com/catalogs/pdf/ptx/2015/Pertronix2015.pdf