Happy Thanksgiving and what a blessing, that in the USA at least we have the freedom to debate and choose whatever technology we want to employ on our antique iron. Headlamps, ignition, sound systems, wheels, whatever.The original post asked HOW to either convert the mechanical tach to electronic or how to convert a mechanical tach drive distributor to electronic, not WHY it shouldn't be done. The question hasn't been answered, and might be interesting, irrespective of theoretical or practical pros/cons. Yes, you could use a mechanical tach drive body and transfer electronic guts perhaps, or use Pertronix.So what is the actual failure rate of Pertronix? I tried to find out years ago, came up empty. I have only seen anecdotal evidence, which is no substitute for fact based analysis. Yes, the heat sink on Pertronix is a compromise and seems completely inadequate, yet they would have ceased business long ago if the failure rate in the field was that extraordinary. I discussed this with Pertronix techs years ago, via a call that our friend John Lazenby helped coordinate. It appears that the majority of failures are caused by incorrect installation , which is "user error." Pertronix wants full steady 12V+ battery voltage, you do not wire direct to coil, the installation instructions are very clear on that. It will tolerate it, but for how long? It punts, you walk. I have it on my '57 392, no issues for 13 years, runs great, don't have to lay over the top of the engine to mess with dual points. Call me lazy. I like it. If it punts, I'll call Hagerty. I will never drive the car in downtown Boston; so I'm not too worried about traffic. Heck, I wouldn't drive anything in Boston, it's nuts there.I'm not going to get into electronic vs. points, advance curves, dwell, any of that - we debated and discussed before. Some of us just prefer electronic ignition over points, and we have the choice to do that. In 45 years I have never had the original circuit spec Mopar Direction Connection box fail on any Mopar. That's anecdotal, of course, but I like them.. Aftermaket boxes , yes, I've had failures. Not sure about the quality or circuit of the current orange box, but you can get a clone of the original box design (from circa 1981) from a guy named Rick Ehrenberg on ebay, made in USA too. I have a spare box just in case, along with a spare ballast resistor in the glove box. I also have a cell phone to call Hagerty. Anything can punt on a 60-70 year old car. Ask Noel about that, he knows.Every modern vehicle is an electronic wonder filled with a gazillion electronic modules, sensors and wiring. Do we worry about it punting every time we drive? Maybe we should. Crank sensor punts, you walk. Cam sensor punts, you either limp or walk. ECU punts, you walk. EMP/TED pulse strikes we all walk, absent Faraday cages. Even small engines - lawn mowers, snowblowers etc. all have electronic ignition. How often does it fail?Nothing wrong with breaker points. We all have choices.Carl B.------ Original Message ------Cc "'John Grady'" <j...@xxxxxxxxxxxxxxxxx>; "'chrysler 300 club'" <chrysler-300-cl...@xxxxxxxxxxxxxxxx>Date 11/29/2025 9:25:51 AMSubject RE: {Chrysler 300} 1961 300 and about point ignitionsYou are both smart fellas. As an EE John discusses concepts that while may have limited practical application and use in occasionally and gently driven 70 year old hobby cars are nevertheless canonized in mans understanding of electrical behavior. This is to say another way its a distinction without a difference.
I never quite understood the romance of driving antique machinery in which its most problematic technologies have been replaced with modern substitutes. Blue Tooth radio, solid state ignition, LED lamps, electric fuel pumps, fuel injection, and Pertronix distributors that allow electronic tach conversions ... Yuck! Gimmie an old car, old through and through except for liquids and gaskets.
Henry makes an observation I've often pondered - why is Chrysler (and other) electronic ignition switching transistor mounted on a generously sized heat sink while Pertronix is little more than a plastic capsule doing the exact same work?
The Corvette folks know well how utterly unreliable Pertronix is and 300 owners should too. If you insist on it, carry a spare plastic capsule or better yet a proper set of points, a condenser and the mounting screws, a match book and a screw driver with you at all times.
Lastly, my career required I hire engineers to keep me out of trouble. These were electrical, mechanical, structural and civil engineers. In my experience engineers typically respect each others disciplines and typically remain in their lane. Adjust your mirror.
Respectfully, fondly, and all that...
Danny Plotkin
-----Original Message-----
From: "henry.schleimer via Chrysler 300 Club International" <chrysler-300-cl...@xxxxxxxxxxxxxxxx>
Sent: Saturday, November 29, 2025 9:58am
To: "'John Grady'" <j...@xxxxxxxxxxxxxxxxx>, "'chrysler 300 club'" <chrysler-300-cl...@xxxxxxxxxxxxxxxx>
Subject: RE: {Chrysler 300} 1961 300 and about point ignitionsOk, Ok , you win the Einstein Prize for Electrical Engineering Theory. I’m just a mere Mechanical Engineer concerned about practical application of theory. For example, spark plug fire is good, spark plug not fire is bad.
I’ll just go back to minding my own business motoring down the road for another 25 years in the mighty Val along with the millions of other cars that have 1V deficient electronic ignition systems, not worrying about our 169/144 sub-optimal sparks. Maybe one day a car manufacturer will see the light and bring back points to save us all! (If you don’t understand this, no explanation will suffice.)
Henry
From: chrysler-300-cl...@xxxxxxxxxxxxxxxx <chrysler-300-cl...@xxxxxxxxxxxxxxxx> On Behalf Of John Grady
Sent: Saturday, 29 November 2025 10:41 PM
To: chrysler 300 club <chrysler-300-cl...@xxxxxxxxxxxxxxxx>
Subject: Fwd: {Chrysler 300} 1961 300 and about point ignitions
Begin forwarded message:From: John Grady <j...@xxxxxxxxxxxxxxxxx>
Date: November 29, 2025 at 7:38:49 AM EST
To: henry.s...@xxxxxxxxxxxxxxx
Subject: Re: {Chrysler 300} 1961 300 and about point ignitionsHi henry ,
its not an argument , its a kind attempt to get you to understand something you clearly do not, Ok?
your statements in original post about 7-8 v are simply totally wrong , deal with it . You do not understand time constant of the coil , far more important than a simplistic and wrong ohms analysis equating more spark with low ohms/ more current . Going for more magnetism / energy is ampere turns , Henry, not just amperes
. Consider that for a lower ohm value in same size coil case there are fewer turns / w thicker wire.to carry the higher current . zero ohms ( think one turn) would give nice high current and no spark “ to keep it simple ”
Use any coil you want for any reason you gin up , i have no problem with that . You traded something off . Your coil also is subject to 169/144 no matter what ohms it has
Einstein said it best : “ for those who do not understand, no explanation suffices ”
best regards ,
johnOn Nov 29, 2025, at 12:51 AM, henry.s...@xxxxxxxxxxxxxxx wrote:
Hi John
I was trying to give members a practical solution to a perceived problem.
As an engineer, I can understand your microsecond-by-microsecond electrical
engineering analysis, but in real life, averages matter and simple solutions
are what’s needed.
Believe it or not, Bosch also hire electrical engineers and they also have
a research facility or two. They also had a GT40 (no R) coil for an
ignition system without a ballast resistor that was designed for continuous
12V instead of the “average” 9V out of a ballast circuit. I wonder why?...
Back to the point, car manufacturers typically supplied the cheapest coil
that was adequate for the job. If an owner increased compression, ran
higher revs etc, the factory coil may have been wanting. Bosch came out
with a better than average replacement “sports” coil that was hugely
successful – at least here in Aust. I can attest to 40 years of
trouble-free motoring with this coil on multiple cars, both points and
electronic. Practice beats theory every time.
Therefore, if you are so concerned that losing one precious volt in an
electronic conversion is going to cause a misfire, just get a better coil
that can cope with it! Unsurprisingly, Pertronix recommend using their
coils.
Remember, if it isn’t broken, don’t fix it! If you don’t get a misfire
after an electronic conversion, what’s the problem!!!
I have only experienced a misfire twice. Once when I bought a cheap no
name control box to replace my Chrysler one (which was working but leaking
goo). Worked fine until 4000 revs and all hell broke loose. Bought a
genuine Chrysler Orange Box instead and the world was at peace again.
Also, my 65 Mustang had its “pink” ignition resistor wire replaced at some
stage with a “pink” copper wire without me knowing. The coil eventually
cooked, sucking in all that 12 V! Luckily, we were only a few blocks from
home when it did and it limped along firing every second cylinder or so. A
Bosch GT40R coil and a ballast resistor fixed that problem.
I suggested the Bosch coil as it looks similar to a factory Chrysler coil
if you spray it with black paint. There are probably other performance
coils around. I know “Uncle Tony” recommends those big yellow square ones.
I think they are ugly.
I agree that MSD runs a successful marketing ploy to flog a system designed
for running nitro in your race engine where the flame can go out and you
need another spark to re-ignite the mixture. You only need one spark for
gas/petrol…
Photos attached show my 25-year-old Bosch coil and the mighty Chrysler
orange box. I’m sticking to points on my 300C and Mustang as I don’t think I
will live long enough to have to change the points on those. If I do, I’m
sure I can spare an hour or so to do it. As for Pertronix, have a look at
the blue heat sink on the Chrysler orange box designed to get rid of the
heat from the transistor. How does Pertronix get rid of this heat inside a
distributor? My theory is it doesn’t and is therefore inherently prone to
heat failure of the electronics. Anyway, that’s my opinion and I really
don’t want to argue further on this.
Henry
<chrysler-300-cl...@xxxxxxxxxxxxxxxx> On Behalf Of John Grady
Sent: Saturday, 29 November 2025 4:18 AM
Cc: club chrysler <chrysler-300-cl...@xxxxxxxxxxxxxxxx>
Subject: Re: {Chrysler 300} 1961 300 and about point ignitions
hi Henry ,
No , you have a very common misconception there .
The reason you measure 8 or 9 V is the meter reads the average value
over time of the volts . ( if a nice analog meter — ,a digital will read
garbage as it samples V in time , about 3 / sec) Varying volts not read
right
Much more complicated than that . When the points are open 12 v appears ,
there as no current in the ballast , no drop ,a full 12 shows up
When the points close it drops in proportion to the resistance present
,reaching about 5 -6 A , or a bit more , indicating about a 1 ohm total ohms
of ballast and coil . If using your .3 ohm coil , only 1.5 v on coil (!)
11.5 on ballast . .More typically coil is around 1 ohm , ballast 0, 6 so
about 5 v . So the average value in time of 5 closed and 12 open is the 8 or
9 .
This is complicated by the ballast is iron wire made to go much
higher in ohms if it gets hot , especially at idle , where you are
measuring this
So why all this ? The coil has a time constant , a physical reality
inherent to all coils around a few milliseconds, It s L ( mH ) divided R .(
ohms) It takes a few time constants for core to “saturate” ,or fill with
stored energy for the spark .So about 4 /1000 sec to fill up for full spark
note with the R “on bottom “ high R means faster saturation of core ( think
if it as filling a bucket — takes time ( current flow) —-that is where the
spark energy is stored. — saturated core happens after about two time
constants , means a full bucket ( full magnetic field actually)
Counterintuitive to many that higher R makes it charge up faster —!
BUT if we make R too big to get this aspect real fast , the total current
once saturated is now made less . Compromise must be made
E ( spark) equals 1/2 L I squared . L is size of coil , note I squared .
Once saturated it is a linear DC circuit all you have is volts divided
by ohms .
For any given setup , ( ohms total) raising the volts 10 % raises the
final current 10 % .
I = V divided by R ..
I is the cause of the magnetic field you get .
So if you lose 1 volt off 13 , you have 12 . Now, due to square , ratio of
spark energy is now 144 to 169 . Physics and EE , done
Pertronix can cost you intensity at higher rpm , but they do have a way
, later on
Why drag racers use 16 v batteries , overcomes that . But ideas to
linearly raise current ( low ohm coil ,has to be used then with no or low
ballast , = not only burn up points ,the 5 A goes up , you just made the
time constant potentially LONGER to get to the higher current.
The real problem in ignitions is there is not enough time to fill the coil
up at over say 4k rpm , spark E starts dropping off . Only a few
milliseconds between sparks at 6000 rpm , might be 1/2 the spark it was at
3000, — equals misfire
The time constant of a coil design does not change much ; larger coil means
longer wire in the coil , L and R both go up . Other way too .both go down
.
It is NOT a transformer ,( although does that too) it is an energy store
device Thicker wire takes more room , for same turns , wire is forced to
be longer ( R up ) etc
Once you have enough to light it there is no return on making more , or ,
say a huge coil at 10 amps same L/R
At idle there are many time constants per spark , current keeps on coming
long after coil is full , coil will get too hot fast ( average current goes
way up ) .. now — a brilliant thing — iron wire gets very hot in ballast (
why ceramic) R goes up with temp protects coil from melting at idle . And
an R shortens time constant too at high rpm, iron is then cool , average
time on is less Awwright
These are engineered systems, messing with them can hurt rather than help
. Correct coil ohms and matching ballast are critical to the trade off .
Mr Kettering knew ALL of this in 1920 . I mean , he just might have
optimized the trades? laugh
And if not , 100 years have led to coil on plug , that fixes the time
constant problem , plenty of time to fill bucket , 8 x as long, don't care
about the 1 volt either - EZ!
Also why many V12 in 30’s have two 6 cyl setups
I actually have a patent on a way of using two coils on a v8 with one stock
distributor , Same functional idea as very old designs with dual rotor ( not
mine) were in the famous DuCoil distributors for flat heads in the 40’s ( 6
volt systems to fight too) Way to go !
7000 rom becomes 3500 to the coil . It was actually the same as two 4
cylinder ignitions, twice the time to fill up . All you need on a V8 .
Another way to fill up better is get more dwell , why mopar dual points ,
higher dwell is directly impacting higher rpm, more time to fill up .
fussy yes , use dwell meter .
Pertronix can get more dwell than points as solid state is fast ( HEI
too) but after all that, the 1 volt thing is still there , but practically
today the increased dwell of electronic does get a lot of the V loss
back. Much Better than single point , big boon to GM guys
But this discussion is about whether mopar stock 300 is ok , and
especially failure modes of “ improvements”
But end of day losing a volt in electronic switch hurts you no matter what
you do , with a normal coil , as saturation current in a given coil WILL be
lower by ratio of the net volts it gets . A squared impact on spark
intensity .
Despite the love of chevy boys MSD is a waste of money .Coil still limits
it Of course chevy boys do not have dual points or a hemi .
An extra spark coming way late ( multiple spark discharge = msd) does
nothing for you, way too late .. sad joke, great marketing story
Maybe they need to adapt 300F distributor to SBC ? 15-20 % more !
Real engineering
means 300B and F went 140 with points, 6500 ok, Petty did ok with Daytona
on points, 1234 finish . Garlits did ok with 50’s points . Nuff said
Magneto is the best , left out of this , but they have points too
They will do the job , will not fail with minor care , if they do , a 10
minute adjustment after 30 k miles? away you go .
# 1 cause of point ignition trouble is junk chinese capacitors sold now
, change that first .Even “burned “ points work ok . Bad cap gives very weak
spark , intermittently too
hope this helps , J
On Nov 27, 2025, at 9:48 AM, henry.s...@xxxxxxxxxxxxxxx
<mailto:henry.s...@xxxxxxxxxxxxxxx> wrote:
Just on the power issue John raised, I would like to correct this
often-repeated quote as the coil does not get 12V/13V with Chrysler ballast
resistor circuits. More like 8V/9V while running. While the numbers are
wrong, John is technically right that there is a proportional power loss.
But he neglects the other side of the equation in that power is also
inversely proportional to resistance. Lowering the coil resistance will
increase the power to the coil, if that’s what you want.
Back in my younger days, the go to hot up mod was to fit a Bosch GT40R
coil. Didn’t matter whether you had a Ford, Holden or Chrysler, that red
coil on the side of your engine showed you meant business! The primary
resistance is 1.2 ohms which is typically lower than factory coils,
therefore more power with a higher voltage output.
I have had one on my Val with factory electronic ignition (pre ELB version)
for 25 years now without any problem. About a year ago I bought one at my
local parts store (in stock/on the shelf) for our 65 Mustang. Having an
aftermarket part available for 40 years tells you all you need to know about
reputation and reliability. Sadly, they now seem to be discontinued…
Probably not enough need for this type of coil any more to justify room on
the shelves.
Cheers
Henry
<mailto:chrysler-300-cl...@xxxxxxxxxxxxxxxx> > On Behalf Of
John Grady
Sent: Thursday, 27 November 2025 4:58 AM
To: Bob Jasinski <rpj...@xxxxxxxxxxx <mailto:rpj...@xxxxxxxxxxx> >
Cc: Allan Zolis <allan...@xxxxxxxxx <mailto:allan...@xxxxxxxxx> >;
Subject: Re: {Chrysler 300} 1961 300 g tachometer question
agree,in fact nothing wrong with points,10k miles no bs ,curve in MSD will
not match stock. Trouble with pertronics if it punts you walk. Maybe a long
wolk. Points and business card you go.Points do not lose the 1 volt of
solid state either. Power in EE goes as square of volts,you lose 144/169 ,
significantly weaker spark
On Wed, Nov 26, 2025 at 12:11 PM 'Bob Jasinski' via Chrysler 300 Club
International <chrysler-300-cl...@xxxxxxxxxxxxxxxx
<mailto:chrysler-300-cl...@xxxxxxxxxxxxxxxx> > wrote:
Allan,
Do yourself a favor and keep the original tach drive distributor. Install
a Pertronix unit, easy to do, you will keep the original look and tach drive
function of the stock distributor. I’ve had one in my G since 2011, I’d
never go back to points.
Bob J
<mailto:chrysler-300-cl...@xxxxxxxxxxxxxxxx> > On Behalf Of
Allan Zolis
Sent: Wednesday, November 26, 2025 4:28 AM
<mailto:chrysler-300-cl...@xxxxxxxxxxxxxxxx> ; Allan Zolis
Subject: {Chrysler 300} 1961 300 g tachometer question
Hi Everyone,
I decided to replace my dual point distributor with a MSD system. My
question is, since this new distributor does not have a drive for the
tachometer cable, (it still lights up) is there a way to either hook up a
drive or either convert this tach to electronic?
Thanks again for any insight you can provide.
Happy Thanksgiving everyone!🍗
--
Allan Zolis
Odessa, Florida
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