Which coil would you use out of these three?

[old31]

With a 6.0 head and with points I am not sure which of these coils is the best. I do not understand the results.
					Secondary	Primary
Brand new Snyder coil					12.7	2.6
Pertronix 1.5 ohm model 40111					9.4	2.4
Delco Remy 1115328					3.3	2.6

[Corley]

What voltage is the car?

[old31]

Corley the car is 6 volt.

[2manycars]

I bet Tom has the answer.

[tbirdtbird]

The primary and secondary readings indicate what ???? Volts, amps, ohms??

The CR and points vs electronic ignition have no bearing on the coil choice whatever..
If you can get 10K volts from the secondary you can run a head up to at least 10:1 compression.

The advent of very high voltage coils came to be because the EPA demanded than engines be leaned out to a near non-combustible fuel ratio; meaning that the mix is so lean it is amazing the motor will run at all. So, for a very lean mix, you now need 30-40KV to jump the gap.....there is nothing there to ionize.

None of this will ever apply to a Model A, thank God. The EPA could screw up a one-car parade

[Corley]

I don't agree with your second sentence. The coil should match up with the electronic ignition module used, pretty closely, or you can burn out the module. For example, I would never use a 6volt coil with no ballast resister, with an electronic module on 12Volts, as the excessive current will surely overheat and burn out the module. You are correct that CR really doesn't matter on this, all our CRs are so low that spark can jump our plug gaps easily.

[tbirdtbird]

" I would never use a 6volt coil with no ballast resister, with an electronic module on 12Volts, "

I never said to do that

clearly if you have a 6V coil and you have a 12V system, then you need a ballast resistor. This truth was never in question
See 11.1

[CarlG]

PERTRONIX Flame Thrower

[BNCHIEF]

x2 for me plus follow Tave's advice as well.

[Tom Wesenberg]

Yes, I do have the answer, but Dave already posted it. I use original coils only, and have been totally satisfied with them.

[plyfor]

Ditto to what tbird states. What's the ohms readings across the wire terminals to meter if you have coils in your possession? See some of the other coil threads. Lots of opinions and discussion on the web and sites about the new coils' quality available, all now made overseas.. The 40111 (1.5 ohm rated) is epoxy filled which some say doesn't allow the heat to dissipate well but can be oriented with terminals down or up. Oil filled coils seem to prefer the terminals up to allow for better cooling (is the Snyders' coil oil filled ?). Is the Delco coil NOS and tar filled based on that product number ? If so, this may be a good option.

[Dennis]

I'd use the Pertronix like Carl probably because I already have and use it and it works fine for me.

[2manycars]

I use the coil that came on the car when I bought it in 1975.

[old31]

For the guys that say Pertronix. Are you saying it due to the ohms readings on the charts, or Pertronix as a name.

Snyders coil I got was not oil filled.

[tbirdtbird]

If you have a 6V system you want a coil with 1.5 ohms across the primary side
If 12V you want to see 3.0 ohms . All coils that we would ever come across are wound at 1.5 ohms. If you have a 12V system and ask for a 12V coil, it comes with an internal resistor to bring it to 3.0 ohms

Or if 12V you can add an external ballast resistor to a 6V coil to bring the ohms up to 3.0.
I do it the latter way, since that internal resistor builds up lots of heat and shortens the life of the coil.
To each his own.

I often do not respond to coil questions because there is so much misinformation out there about how it all works, on just about every forum I have ever been on. Which is unfortunate since in reality it is all very easy

Another myth is that you need a different coil depending how how many cylinders you have

[BNCHIEF]

Dave simple advice not something to overthink.

[BNCHIEF]

I like the petronix coil because of the voltage, i believe you are running the zipper distributor just match the coil up with the electronic ignition you have in the distributor I am guessing you have an ignitor I look at that give petronix a call and go with their recomendations. I believe the petronix is oil filled and the terminals need to face up, epoxy filled coils can face the terminals down.

[Corley]

Well this is a no brainer, since you have Petronics ignition, just use the Petronics coil. They should match up well. (Though, probably any of those will work.)

[plyfor]

pg 60 of Pertronix catalogue with parts numbers.

[Dennis]

I use a Pertronix because my system is currently 12 volt. I have the same epoxy filled coil on another car of mine. I do have an original coil to when my car was built with the angled posts that was on the car and I can only assume it was still a working coil but I never bothered to see if it was good or not.

[old31]

Tbird, you said "If you have a 6V system you want a coil with 1.5 ohms across the primary side". So, the question is, is a coil with a 2.5 ohms or 3.5 ohms a better coil or worse because it has a higher primary number?

That is where i was going with my initial question, poor wording on my part. I was looking only for an answer based solely on the numbers, not brands or oil filled or gel.

[tbirdtbird]

a coil with a reading of 2.5-3.5 ohms would be intended for a 12V system.
There would be too much resistance on a 6V system to give a really good spark

The higher the ohms the greater the resistance

[plyfor]

I've been following this thread because of issues we've had with 2 new Standard and Lucas oil filled internally resisted coils for some reason getting very hot (for 12 volt systems) and engines suddenly stopping, then restarting when the coils appear to cool off. Also, when testing off the car, we've used a cheapo v/ ohm meter and counter checked with our Fluke professional grade. The cheapo was off by .5 to .7 ohms. We tested an older Porsche 12 volt internal resisted recycling yard Bosch (tar filled) coil for 3 ohms across the 2 wire terminals, which was dead on,--- the other 12 volt new oil filled ones mentioned displayed varying readings (overseas made) . We installed the Bosch coil on our A and it is only warm to the touch, possibly similar to the epoxy filled coils, which we haven't tried and tested. Would be interested if others have had issues with the newer oil filled coils.

[old31]

a coil with a reading of 2.5-3.5 ohms would be intended for a 12V system.
There would be too much resistance on a 6V system to give a really good spark

The higher the ohms the greater the resistance

Tbird, thanks. That is the type of answer I was looking for. So, am I guessing that the high secondary readings are also not good for a 6 volt?

[tbirdtbird]

Generally we do not worry about the secondary readings (the high voltage side). There can be variation there. The thing to be certain about is what the primary readings are in relation to whether you are 6V or 12V.
Then wire it up, and if it throws a good spark, you are good to go.
Good spark means: blue and can jump a 1/4" gap
A yellow or orange spark is weak and either the coil is failing or the capacitor is failing

I don't think I have ever even measured the secondary ohms on any coil

[old31]

Tbird thanks again, that is exactly what I was looking for.

[Bikerider58]

This thread got me thinking so I checked my coil and noticed top cracking. No worries as I saw a coil in the box of parts.

Checked it and found an open primary. Why do some people save bad, not repairable parts?

[JDupuis]

These same people that save some parts, are also of the mindset that, if I wash the car, it will run better. (Or at least they hope!). Jeff

[Bikerider58]

It may not run better, but it will go faster. The dirt creates extra drag. So, a clean and waxed car is faster.
For bikes, chrome does the same.