FWIW, I put a Pertronics in my '74 (Delco dist) about 10 years ago. I left
the existing coil, and hooked up the Pertronics directly to the coil. It
has seemed to function fine since then. YMMV, etc.
BillG
-----Original Message-----
From: spitfires-bounces@autox.team.net
[mailto:spitfires-bounces@autox.team.net] On Behalf Of Greg Rowe
Sent: Wednesday, January 15, 2014 6:53 PM
To: Spitfires
Subject: Re: [Spits] pertronix
I
replaced my dead Crane unit with a Pertronix about a year ago. I didnt
remember there being any difficulty with determining which Pertronix to get,
however there was a lot of confusion about the right ignition coil. You may
already know this but if not, it may help.
Pertronix
talks about 1.5ohm and 3 ohm coils which correspond to 6 volt and 12 volt
coils (the 12 volt necessarily has more windings which results in the higher
resistance). Depending on what year/model you have, your spitfire may have
come originally with either a 6 volt or a 12 volt coil. In addition, it may
have been changed by a previous owner so double check.
Both
coils put out the same voltage out of the ignition wire to the distributor,
the difference is the voltage that they need to operate, the amount that
should be seen on the + terminal. You may wonder why Triumph would use a 6
volt coil in a 12 volt system and that is because when you are starting, the
heavy draw of the starter (and lack of alternator
charging)
reduces the available voltage below 12 volts. You get a hotter spark to
assist with the difficult task of firing the engine by temporarily
overloading a 6 volt coil than underloading a 12 volt one.
So
normally a 12 volt coil gets 12 volts (nominally) ALL the time on its +
terminal. The 6 volt gets the full 12 volts when cranking and then only 6
volts (through either a ballast resistor or ballast wire) when running.
What
does all this have to do with the Pertronix unit? When you install the
Pertronix, it will tell you to hook up the red wire at the + terminal of the
coil and the black wire at the - terminal. It will also tell you that you
need a 3.0 ohm coil, e.g. 12 volts.
No one that Ive spoken with is really
sure, but it appears that
Pertronix is saying that their unit needs a constant
12 volts to operate. The coil is a convenient place to take it from even
though youre really just using a common junction, theres nothing magical
about the 12 volts at the coil as compared with anywhere else (although you
do want it to be switched in synch with the ignition). And I cant think of
anything special about the terminal, the Pertronix is just grounding the
coil so it produces a spark and I dont see how the unit could care whether
the coil is 3 ohms or 1.5. So what I did was leave the 6 volt coil in place
and take a 12 volt source for the red wire from the Pertronix from the
remnants of the factory electronic ignition. So far thats worked. Ive
also heard that some folks have just run the Pertronix on 6 volts and it
seems to work but whether it shortens its life, who can say?
So
bottom line:
If
you have a 12 volt coil and no ballast wire, you are good to go.
If
you have a 6 volt coil and a ballast wire, you can
-
Bypass the ballast and replace the coil with a 12 volt (lose advantage of
hotter spark when starting)
-
Keep the 6 volt and find another 12 volt ignition source for the Pertronix
(not recommended by them but seems to work)
-
Keep the 6 volt, hook up to 6 volts and see if it actually makes a
difference (uncharted waters).
I
hope this helps. Good luck with it! Greg Rowe > From: dave@ranteer.com
> To: spitfires@autox.team.net
> Date: Tue, 14 Jan 2014 16:56:34 -0600
> Subject: [Spits] pertronix
>
> hi. have a 75 spit; was converted to allison ignition which is pretty
dead.
> I want to order a pertronix, but it appears there are numerous choices.
>
> how do I choose????
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