High-Voltage Coil Creates Hole in Pistons?

I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
intake, carb, and cam. I read a post somewhere that adding a
high-voltage coil can cause the spark to jump and thus burning a hole
in stock pistons. The idea is that the engines were not designed to
handle more than 30,000 volts. I just want to know if anyone has an
opinion about this? Do you agree with this assessment?

64bird wrote:
>
> I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
> intake, carb, and cam. I read a post somewhere that adding a
> high-voltage coil can cause the spark to jump and thus burning a hole
> in stock pistons. The idea is that the engines were not designed to
> handle more than 30,000 volts. I just want to know if anyone has an
> opinion about this? Do you agree with this assessment?

I can't see why an arc would prefer to jump a relatively
large distance to a piston top that's not as well grounded
as it would to the small distance to the perfectly grounded
spark plug tip.

JazzMan
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On Sat, 26 Mar 2005, 64bird wrote:

> I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
> intake, carb, and cam. I read a post somewhere that adding a
> high-voltage coil can cause the spark to jump and thus burning a hole in
> stock pistons. The idea is that the engines were not designed to handle
> more than 30,000 volts. I just want to know if anyone has an opinion
> about this? Do you agree with this assessment?

Of course not. It is based on gross ignorance of how secondary ignition
voltage is determined. Putting in a "high voltage" coil and changing
nothing else won't change the secondary voltage one bit. Opening the spark
plug gaps will increase the voltage. The spark will NEVER jump to the
piston top unless the spark plug's side electrode is missing (as in
"gone", broken off).

The power (volts x amps) required to jump any given plug gap under any
given conditions is constant. You cannot "force" more volts or more amps
through the gap, for as soon as the power reaches that required to jump
that particular gap, it will jump.

A "high performance" ignition system *can* supply greater voltage and/or
current, but that doesn't mean that it will. The difference isn't what
goes across the gap of the spark plug under ordinary circumstances, it's
what happens under extraordinary circumstances.

Increasing the spark plug gap, increasing the compression, running a dirty
spark plug (either through neglect or because some other thing you've
changed allows the plugs to get dirty, e.g. a "big" camshaft left to
idle).all these things increase the amount of power required to jump the
gap. A stock ignition system may not be able to provide that much power,
with the result being a misfire. A high-performance ignition system has
greater power potential and so will go ahead and fire the plug.

This is very, very commonly misunderstood, thanks in large part to the
marketing tactics used in selling "high performance" (actually high
performance POTENTIAL) ignition components.

DS

64bird wrote:
> I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
> intake, carb, and cam. I read a post somewhere that adding a
> high-voltage coil can cause the spark to jump and thus burning a hole
> in stock pistons. The idea is that the engines were not designed to
> handle more than 30,000 volts. I just want to know if anyone has an
> opinion about this? Do you agree with this assessment?
>

Absolutely not. Spark gap is generally .035-.045".
The distance from the end of the plug to the piston
top would be at least 4-5 times that in a stock engine.
Can you imagine an engine running with a spark gap of
..5"? It would take a heck of a lot more voltage than
30K, and a missing electrode, to create a spark like that.
I'm not an electrical engineer, so I can't explain
the exact theory behind it. But I am a car guy, so I
can explain the application.
Your secondary ignition system will create as much
spark as the engine requires, regardless of what it's
capable of. If you have good fuel, low compression,
low rpm's, and a small plug gap (like .035), you don't
need a whole lot of energy to make a good spark. Say
10K volts. So that's all it makes. You may have a 50K
coil and 10mm wires, but you'll still only make 10K
volts, because that's all it needs.
Now, start adding things that make a spark more
difficult to generate - like nitrous, high compression,
high rpm's, etc. Now that high powered ignition system
comes in to play. The engine needs 50K volts to
generate a spark, so it better be capable of that.

--
..boB
1997 HD FXDWG - Turbocharged!
2001 Dodge Dakota QC 5.9/4x4/3.92
1966 Mustang Coupe - Daily Driver
1966 FFR Cobra - Ongoing project

On 26 Mar 2005 19:39:51 -0800, "64bird" > wrote:

>I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
>intake, carb, and cam. I read a post somewhere that adding a
>high-voltage coil can cause the spark to jump and thus burning a hole
>in stock pistons. The idea is that the engines were not designed to
>handle more than 30,000 volts. I just want to know if anyone has an
>opinion about this? Do you agree with this assessment?

If you replaced your stock coil with something along the lines of an
idustrial arc welder you might have a problem but no ignition coil is
going to burn a hole in your piston.

Steve B.

Thanks for all the input. I'll install the coil and electonic ignition
tomorrow.

64bird wrote:
> I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
> intake, carb, and cam. I read a post somewhere that adding a
> high-voltage coil can cause the spark to jump and thus burning a hole
> in stock pistons. The idea is that the engines were not designed to
> handle more than 30,000 volts.

Engines have no problems handling 80KV (the highest voltage I've heard
being used intentionally), but some ignition systems can't stand more
than about 35KV-40KV and will leak electricity through the wire
insulation, boots, distributor coil, and rotor (leaks cause those 2 to
crack and require replacement) and sometimes even cause an ion cloud
inside the cap that can shut off the engine temporarily (a reason for
very large diameter caps).

Plugs can typically fire at 5KV-20KV, and high-voltage coils generally
aren't a good way to improve ignition, but solid-state ignition is,
mostly since it lets the voltage turn on much more quickly and makes
the plugs fire before spark energy is drained off by deposits on the
plugs. CD ignition turns on the fastest, but for normal use it's not
an improvement over other solid-state ignition, and if you try it be
sure it's designed to limit its voltage to under 40KV or so.

"Daniel J. Stern" wrote:
>
> On Sat, 26 Mar 2005, 64bird wrote:
>
> > I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
> > intake, carb, and cam. I read a post somewhere that adding a
> > high-voltage coil can cause the spark to jump and thus burning a hole in
> > stock pistons. The idea is that the engines were not designed to handle
> > more than 30,000 volts. I just want to know if anyone has an opinion
> > about this? Do you agree with this assessment?
>
> Of course not. It is based on gross ignorance of how secondary ignition
> voltage is determined. Putting in a "high voltage" coil and changing
> nothing else won't change the secondary voltage one bit. Opening the spark
> plug gaps will increase the voltage. The spark will NEVER jump to the
> piston top unless the spark plug's side electrode is missing (as in
> "gone", broken off).

100% Correct.

>
> The power (volts x amps) required to jump any given plug gap under any
> given conditions is constant. You cannot "force" more volts or more amps
> through the gap, for as soon as the power reaches that required to jump
> that particular gap, it will jump.

Actually it is voltage only. The breakdown voltage required to ionize
the path and create the spark is constant, the current passing through
that ionized path and therefore the energy generated in the spark is
variable.

Consult the specs on any constant current welding power source (Stick /
TIG). You can hold a constant arc length which will determine the
voltage potential across the arc, while widely varying the current
flowing which will vary the amount of heat being applied to the weld
(TIG foot pedal).

>
> A "high performance" ignition system *can* supply greater voltage and/or
> current, but that doesn't mean that it will. The difference isn't what
> goes across the gap of the spark plug under ordinary circumstances, it's
> what happens under extraordinary circumstances.

One thing that a "high performance" ignition could do is reduce fouling
of plugs by providing a higher current to the spark, increasing the
probability that contaminants will be burned off of the plug electrodes.

>
> Increasing the spark plug gap, increasing the compression, running a dirty
> spark plug (either through neglect or because some other thing you've
> changed allows the plugs to get dirty, e.g. a "big" camshaft left to
> idle).all these things increase the amount of power required to jump the
> gap. A stock ignition system may not be able to provide that much power,
> with the result being a misfire. A high-performance ignition system has
> greater power potential and so will go ahead and fire the plug.

Voltage, not power. Contaminants provide insulation increasing the
breakdown voltage. A higher voltage is required to create the spark. A
higher current spark may be able to burn off some of the contaminants.

>
> This is very, very commonly misunderstood, thanks in large part to the
> marketing tactics used in selling "high performance" (actually high
> performance POTENTIAL) ignition components.
>
> DS

Key point - Never trust marketing drivel. The product may well be good,
but try to find true specifications or "white papers" written by
engineers, not marketers.

Pete C.

"64bird" > wrote in message
oups.com...
>I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
> intake, carb, and cam. I read a post somewhere that adding a
> high-voltage coil can cause the spark to jump and thus burning a hole
> in stock pistons. The idea is that the engines were not designed to
> handle more than 30,000 volts. I just want to know if anyone has an
> opinion about this? Do you agree with this assessment?
>


Holes in pistons would not be caused by a "high energy ignition system" but
usually
by a overly lean air/fuel mix in the cylinders, like an intake leak or over
lean carb mixture.

just a bit of common engine performance 101

64bird wrote:

> I have a 64 Thunderbird with a rebuilt 390 (stock) with aftermarket
> intake, carb, and cam. I read a post somewhere that adding a
> high-voltage coil can cause the spark to jump and thus burning a hole
> in stock pistons. The idea is that the engines were not designed to
> handle more than 30,000 volts. I just want to know if anyone has an
> opinion about this? Do you agree with this assessment?
>

Seems to me there are other things the spark can jump to other than the
piston. The gap should be much less than distance from spark plug
electrode to piston. Why is it not jumping the spark gap? If it jumps
that, it won't go to piston.