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Discussion Starter #1
I just installed a Pertronics ignition system. Should I increase the spark plug gap or leave it as is? I have 67 396/350hp stock engine. Thanks

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67 SS 396
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Go with what they recomend, however, if you are changing from points to Pertronics (you probably are) then I would increase the gap from what it was with points. I feel the wider gap as long as no missfire is incurred, provides a better chance for the mixture to be ignited, since it increases the size of the spark. This will cause your coil to work a bit harder, but I feel it is worth it.
 

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Discussion Starter #3
How far would you gap them? .045?
I appreciate your help.
 

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Stay with the stock .035, more gap with the Ignitor can cause overheating of the coil and module. These pieces are not High-Energy, high output, just point eliminator systems. Too much plug gap causes the system to work way too hard.

Sorry if others dis-agree, I remove lots of blown up Ignitors every month from stuff like this. Keep the gaps at stock levels, .035 max, and leave the ballast resistor or resostor wire in place, it'll have a chance to live, then.
 

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So far, I've not seen this problem occur on the PerTronix units I've installed. Although most of the cars have been low usage cars. I've talked to Neil Wilder, the PerTronix engineer, many times over the years and he has indicated that a .040-.045 gap is OK.

By the way, the correct spelling is ---PerTronix, with a capitol T and an x.

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Tom Parsons



[This message has been edited by DZAUTO (edited 11-29-99).]
 

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Well, he might be the engineer, but I see these things when they are in the field, in (HaHa) use, and what causes their failure in every-day life. What I have found is .035 lets them live. More gap they don't like.
T,X, G, Q, RUN-DMC, who cares.

Even a stock HEI is much better than one of these drop in disasters.

Just my educated and many years experienced opinion.
 

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IgnitionMan,

What does plug gap have to do with frying a PerTronix Ignitor?

All the Ignitor does is to tell the coil when to fire high voltage to the plugs. The Ignitor would do the same job whether the plugs had zero gap, .035, .045, or no plugs at all. Pickupis powered by low voltage from coil (+), about 9V. It then sends that back to the coil (-) to tell it to fire the plugs. Plug gap means nothing here.

The coil is the link that is effected by increased plug gap. Bigger gap, the more voltage it takes to jump the gap. More voltage = fatter spark. More voltage also means a burnt up coil, if it can't withstand the added load. An aftermarket, higher output coil can withstand the extra load.

Someone please correct me if I'm wrong.
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??michael j Team Chevelle Gold #77
70 Chevelle SS396 4sp, Fathom Blue/White Stripes - Canadian built

[This message has been edited by michael j (edited 11-29-99).]
 

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Plug gap is directly related to resistance and heat production. When any ignition system is allowed to overwork itself by being made to bridge a too-wide plug gap or fire two plugs at one time by magnetic flux crossover from one plug wire to another, the coil and module get into problems with heat, and failure will follow, just a matter of time.

When the ignition gurus tell everybody to run plug wires not next to, but across each other and keep sequential firing cylinder's wires separated, they are making sure the coil and module are not forced to overwork and overheat from firing too much of a spark gap load.

Since a coil will try to make a module produce more output to fire the overload of both plugs at one time, twice, the heat created will cause module failure.

Everyone knows to not remove a plug wire while an engine is running, it overloads the coil and module, by not letting the coil voltage dissipate through the plug gap. This makes the coil try to produce a spark that would bridge the larger gap, then can't find one to bridge, and then fires within itself, causing an insulation layer short.

Internal coil layer shorts don't always cause the coil to stop working altogether, and when they still funtion, they require more current to make the same output they made when they weren't damaged. For the damaged coil to make the greater output the damaged coil thinks it needs, it calls upon the module to help make more spark to bridge the larger gap that isn't there, and more heat, failure.

Doesn't make a difference who makes the coil, module, or anything else, if the gap is too big, or a wire is disconnected while the engine is running, or crossfiring is encountered, the resistance used in either the coil and/or the module is raised, heat goes up, and parts fail.

I have found that the lesser output units have a smaller threshhold of resistance to the changes that cause failure than the better systems have.

One of the things that cause system failure is exceeding the tolerance of a certain product's level of operation. With the Ignitor, I have found it wants a ballast resistor to work right and live, and a stock coil and plug gap to live a long life.

Everyone should do exactly what they want with their ignition systems, coils, wires and plug gaps. I'll just keep changing the ones that have been forced to exceed the level they want to operate in, and have failed. Just don't be surprized when it happens, there is a definate reason for it.

That's my job, to fix them when they are forced to break.

[This message has been edited by IgnitionMan (edited 11-29-99).]
 

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I'm happy with PerTronix in my 70SS-454; but I only installed it to do one thing: eliminate points/condenser replacement and dwell setting while retaining original distributor. It does this well.

For hotter or longer spark, you have to obviously use a better coil with more inductance, higher turns, heavier gauge
wiring, better insulation, and heat dissipation; but since the coil is basically a transformer, taking 12 volts from the primary up to 40,000 volts in the secondary
involves a proportionate amount of current
flow in both windings. Everything coming out of the secondary winding came from the primary, after overcoming parasitic and resistance losses. This translates back to how much current flows from +12 thru a ballast if any, thru the coil primary, thru the points or points eliminator (PerTronix) to ground during each spark sequence. Individual current spikes can be relatively high; but since they are short, the average current flow is small (2 to 10 amps). This is
what they are talking about regarding unreliablity. The PerTronix has a final output transistor inside its case that's doing the actual work. It has to handle the
spikes of current, emf backdrive from the
secondary collapses, and the overall heating
effect of the average of all the work. To survive it has to dissipate this work as heat into the baseplate of the distributor, which
is absorbing heat from the engine. So just dont expect too much from a PerTronix. If you need a much bigger spark, with reliablity, you probably need to plan a complete bigger ignition system: ignition box, distrib, coil and wires as a system from one of the big 3: MSD, Mallory, or Accel.

Just adding PerTronix isn't going to increase spark plug voltage, current, or duration enough to warrant increasing plug gap much.

Hope this helps...........
 

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Terry,

Thank you.

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??michael j Team Chevelle Gold #77
70 Chevelle SS396 4sp, Fathom Blue/White Stripes - Canadian built
 

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Discussion Starter #13
Thanks for all the great advice. This is a great site and group of people.
 

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Indulge me just one more time on this, please.

From National Dragster, Volume 40, Issue 12, November 12, 1999, page 18, Notes section, and I quote,

"John Smith, tuner of Randy Parks' Fluke/Rydin Decal dragster, traced their inability to qualify the week before in Dallas to bad plug wires that missed under load and burned up the spark boxes. With no other changes for the following week in Houston, Parks qualified No. 9 with a career best e.t. of 4.61".

Upon speaking with both Vandergriff and Smith at Pomona, this ignition technition was assured the wires that went bad at Dallas was from plug wire resistances rising to above the operating threshholds the spark boxes could handle, and failure of those parts slowed the car down. Replacement of the plug wires, and the plug wire damaged spark boxes, made the performance return. Confirmation of the resistance rise in 14 of the 16 plug wires was given to me by the plug wire manufacturer at the Pomona event after I initially spoke with Bob and John.

This is to confirm that ANY problem that raises resistance/heat within the spark system, even on the lowest form of automotive ignition system, can and will cause component failure. Including failures to and caused by wire sets, modules, coils, caps, rotors, voltage spikes and all other ignition related problems.

One last thing, in terrys' post, he says that performance coils make 40,ooo volts, this is a true statement for CDI ignition systems, but not for ones like the PerTTTTronix. The dwell into the coil must be changed to allow for the coil to make more voltage than the plug needs to fire, and the PerTronix doesn't do this. It does give uniform dwell, but no other advantage is offered (except elimination of point replacement/resetting-nice-but I want more from a replacement electronic ignition). Since PerTronix units like STOCK coils, and since the dwell isn't bolstered with it, the performance coils are a waste with them, and they simply won't make anywhere near the 40,000 volts advertizing untruth the general public wants to insist on believing. They make little more than stock point system plug firing voltages. A-ha, you say the step-up is in the secondary side only, not completely true. If this were a given in ignition coils, we'd all still be using 6 volt electrical systems in all our cars with special coils, as they tried in the early fourties through the mid-fifties. We don't. It takes a different dwell saturation to make the secondary side performance coil stepup turns ratio collect and store enough power to make the large voltages, and drop-in setups don't. Look at a scope with total voltage output next time you work on one of these systems, then tell me what you see. I already know what you will find. Output voltages in the point ignition range, 6,000 to 9,000 volts at the plug only, not 40,000 volts. Definately a help, but not enough for me.

That's the way it works. Thanks for your time.



[This message has been edited by IgnitionMan (edited 11-30-99).]
 

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After all the above, we're gettin down to the answer.
Terrys is correct that any coil (or transformer) will have proportional current (amperage)on both the low voltage and high voltage sides, thus when you increase current on one side, you cause an increase on the other.However , widening a spark gap raises the required VOLTAGE while it may or may not affect the CURRENT (amperage).As Ignition Man points out, dwell, saturation, internal shorts, and more are also serious contenders in this equation. Basically, ignition spark is a very complex system where each part affects the others. Very complex calculations and test equipment are required to successfully analyze this system. As stated above and in their advertisements this is a POINT ELIMINATOR device.
SET THE PLUG GAP WHERE PerTronix SAYS. As always, follow the manufacturers recommendation if you want the device to do what it is supposed to,- OR - Feel free to experiment, but don't blame the manufacturer if it doesn't meet your expectations.

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Gotta have a Chevy !In Durham N.C.
Why is there never enough time or money to do it right the first time, but ALWAYS enough to do it over?
Make it look the way you like it, forget what the other guys say!
 
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