spark plugs

Wider gaps tends to retard spark some if that matters any here.
The air craft people test their dual ignitions systems which run dual plugs, rpms lower when just one system/plug firing. Spark igniting does matter if your engine can use it, either because of rather poor tune or rather great one.

Hi Jim,

There's a discussion on the Champion website about the two filtering methods. Suppressors use an inductor to filter the high frequencies, as opposed to a resistor to limit current. It is a technique that is particularly effective when the source is capacitive, since it forms a resonant circuit. With an inductive source, like a coil, it's just the wrong technology. For high-output inductive sources, resistive filters are much more effective.

DogT,
PS gap is .028
Marshal

rick in seattle said:

Hi Jim,

There's a discussion on the Champion website about the two filtering methods. Suppressors use an inductor to filter the high frequencies, as opposed to a resistor to limit current. It is a technique that is particularly effective when the source is capacitive, since it forms a resonant circuit. With an inductive source, like a coil, it's just the wrong technology. For high-output inductive sources, resistive filters are much more effective.

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I don't guess I have ever used an actual suppressor plug. The info I found was from an old Sun diagnostic manual [1982]. They showed the different scope patterns seen with inductive plugs. [mainly lower firing line]
They also said suppressor plugs were not used much anymore. Are they still in use? Jim

Jim,

My input here is from the physikey side, and not the automotive side. I don't want to misrepresent my competence. Still, as a boater as well, it looks as if suppression plugs are a legacy item for a few old CD marine systems, and have little relevance to automotives. The question arose from this thread on the forum. Suppression plugs are not resistive plugs. Surely no one uses these things in Nortons, do they?

Rick, I don't suspect most people know they exist or the difference. Thanks to your reply I now do. And what is an engine but physics applied. Jim

Marshall,
Thanks, I'll try a set of the AP64's when I get it on the road this coming spring. I'm still running with all original condensers, coils, wire and points. No kickback. I'm sure something will give up the ghost at some point though at 41 years old. Wish I was still 41.

Dave
69S

DogT said:

Marshall,
Thanks, I'll try a set of the AP64's when I get it on the road this coming spring. I'm still running with all original condensers, coils, wire and points. No kickback. I'm sure something will give up the ghost at some point though at 41 years old. Wish I was still 41.

Dave
69S

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I have used NGK standard, NGK Iridium, Nippon Denso and Champions never really noticed any difference....

plj850 said:

DogT said:

Marshall,
Thanks, I'll try a set of the AP64's when I get it on the road this coming spring. I'm still running with all original condensers, coils, wire and points. No kickback. I'm sure something will give up the ghost at some point though at 41 years old. Wish I was still 41.

Dave
69S

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I have used NGK standard, NGK Iridium, Nippon Denso and Champions never really noticed any difference....

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So have I, on the dyno with full monitoring. The only differences I have seen are slight differences in heat range temperature that may make some foul a little easier if the tuning is poor. Horsepower and combustion efficiencies all stay about the same. Jim

Given that fuel atomization is never perfect, especially when you consider different engine speeds, temperatures, loads, and altitudes, as a matter of theory, I've always held that a wide gap and a fat spark were better.

If you dump the resistor and widen the gap, you can have a fat and long duration spark. So, why count on a small quick kernel to ignite swirling gasses of differing air/fuel ratios?

As easy as it is to get to the plugs, give me a file and a standard plug. Maybe a projected nose model. Narrow the ground electrode slightly, shorten it too, leave a sharp edge on its under side, and sharpen the center electrode too. Gap it wide, to the point of misfire at WOT in 4th on that long hill. Old school silver plated copper wires are nice too.

MarshalNorton said:

Have worked well in my combat NGKBP7ES and most recently Auto Lite AP 64's
Marshal

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Marshall i have no comment on you input this time - but for some reason the pic of your bike is much more appealing to me for some reason....

hummmmm....

Xebackslider, real factory Commandos like it like you do it and is how I got used to doing plugs from go carts to outboards and old V8's. There is a funny side effect beside static on near by radio's, you LED turn signals can turn into syncopated timing lights, blinking out the rpms in dashes. Next thing to discuss is effects of plug gap direction indexing. A non issue thank you on surface gap wonders I've tried and keeping eye out for again. Ms Peel's digital optical CD ignition will get 3 adjustable strikes per power stroke in case that matters.

mikegray660 said:

MarshalNorton said:

Have worked well in my combat NGKBP7ES and most recently Auto Lite AP 64's
Marshal

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Marshall i have no comment on you input this time - but for some reason the pic of your bike is much more appealing to me for some reason....

hummmmm....

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Something about it -that yellow just doesn't stand out like it used to. Jim

The ap64 plug is 2 to 3 heat ranges hotter than the recommended plug for a Norton. Be careful. Jim

comnoz said:

The ap64 plug is 2 to 3 heat ranges hotter than the recommended plug for a Norton. Be careful. Jim

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Also reportedly a "suppression" type plug.

comnoz said:

The ap64 plug is 2 to 3 heat ranges hotter than the recommended plug for a Norton. Be careful. Jim

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Rick and Jim, thanks for the 411 on Resistor vs Suppressor plugs. How about heat range? I've heard everything from burning holes in pistons to pre-ignition.

Heat range can be a real big issue, much to my surprise at first thinking it only related to how well a plug resisted fouling w/o melting. Turns out plug is a major heat path to cool that head area and can lead to holed pistons if not enough.
How does one heed the good advice here - to be careful of increased heat/hard plug? A maxed out engine should be very close too or even a bit into detonation zone.

bpatton said:

comnoz said:

The ap64 plug is 2 to 3 heat ranges hotter than the recommended plug for a Norton. Be careful. Jim

Click to expand...

Rick and Jim, thanks for the 411 on Resistor vs Suppressor plugs. How about heat range? I've heard everything from burning holes in pistons to pre-ignition.

Click to expand...

What make a plug consider to be a hot plug is the fact that the electrode has a long path to the cool metal around it. Water cooled engines generally run a "hot" plug because the head is cool and draws the heat from the plug. Air cooled motors generally need a cooler plug because the head is hotter. If you run a plug that is too "hot" then there is the possibility of the electrode reaching a high enough temperature under hard use that it begins to glow. At that point it will ignite the fuel air charge before the spark happens causing dramatic and serious engine damage such as holed or siezed pistons.

Norton motors generally use a NGK heat range 7 for normal use or 8 for hard use. Autolights #64 plug equates to a heat range 5 in NGK.
There are other factors that go into determining whether the plug will reach dangerous temperatures such as plug projection but I would think a plug of that heat range would be in the danger zone under heavy load. I have not tried app64 plugs.

You can make a plug run cool by running a rich mixture but that will take away a lot of power and fuel economy.

Any Norton motor I have tuned for maximum performance needed a NGK #9 or #10 plug to keep the electrode cool enough. Jim

Reading on this is good. See here plug #19 http://www.dansmc.com/Spark_Plugs/Spark ... talog.html
Than see second pic here: http://www.dragstuff.com/techarticles/h ... plugs.html
That is what I was aiming at. I have gone 220 miles at 80MPH twice with the bike no stops 5 gallon tank no problems but that doesn’t mean you can. Do what you like check often.

I've studied these two articles before. There's more to it yet. Too high a heat range can damage w/o being a source of pre-ignition/detonation. Also the surfaces reviewed in articles are for good down/dirty reading but best place to see average combustion mix is at base of porcelain by light and fibreoptics or slicing. Likely over kill in our stuff but maybe not. Also realize new fuel is cleaner leaner burning than when those charts were current. We have to recalibrate our views and not expect as good of guidance even then.