1.5 or 3.0 ohm ignition coil with Pertronix conversion

[hawkeyestoob]

I have done a quick search of this forum and did not see an answer to this.
I am looking to add a PerTronix Ignitor 1381A on my 67 Belvedere with a 318 and change out the coil. What is the best coil when doing this? Do I go with the 3 ohm coil and bypass the external ballast resistor or do I use the 1.5 ohm version and keep using the ballast? Are there any compelling reasons to do one over the other or is it just a personal preference?
Thanks

 

[toolmanmike]

@HALIFAXHOPS will know

 

[Darter6]

Usually the Pertronix 1381A you still use the ballast.I would use the 1.5 and have on many cars. The Pertronix II and III you by pass.
The 3 ohm is Pertronix recommended for 4 and 6 cylinder engines.Did a few Slant 6 Pertronix conversions with a 3 ohm without a problem
I have run 3 ohm on V8 Mopar ignitions and by passed the ballast with no ill effects. Even drove the cars cross country.
I am not sure if Pertronix and the 3 ohm V8 would be a problem. Can't see why it would not work.

 

[hawkeyestoob]

Usually the Pertronix 1381A you still use the ballast.I would use the 1.5 and have on many cars. The Pertronix II and III you by pass.
The 3 ohm is Pertronix recommended for 4 and 6 cylinder engines.Did a few Slant 6 Pertronix conversions with a 3 ohm without a problem
I have run 3 ohm on V8 Mopar ignitions and by passed the ballast with no ill effects. Even drove the cars cross country.
I am not sure if Pertronix and the 3 ohm V8 would be a problem. Can't see why it would not work.

Thanks for this.
You have confirmed what I was thinking and I would say that I am leaning towards using the 1.5 ohm version and keeping the ballast to keep everything as stock looking as I can. This is a weekend cruise, not anything that I am looking to get maximum performance out of so reliability and ease of starting are the goals.

 

[RJRENTON]

I have done a quick search of this forum and did not see an answer to this.
I am looking to add a PerTronix Ignitor 1381A on my 67 Belvedere with a 318 and change out the coil. What is the best coil when doing this? Do I go with the 3 ohm coil and bypass the external ballast resistor or do I use the 1.5 ohm version and keep using the ballast? Are there any compelling reasons to do one over the other or is it just a personal preference?
Thanks

Why not just call Pertronix and ask them your question and if a ballast resistor is required and it's value and the best coil to use, rather than the opinions of others. That way you'll have accurate information rather than guesstimates or hearsay and have a reliable system......just my opinion......
BOB RENTON

 

[hawkeyestoob]

Why not just call Pertronix and ask them your question and if a ballast resistor is required and it's value and the best coil to use, rather than the opinions of others. That way you'll have accurate information rather than guesstimates or hearsay and have a reliable system......just my opinion......
BOB RENTON

That is a valid point Bob and I still may do that.
But I will point out that I asked that question here after doing a search because I suspect that I am not the first or the last person who will have this question. I see the collective wisdom and real world experience of the members in this type of forum as a great resource. A bonus for me is the fact that they are not tied to a specific vendor or product. In my mind this combination adds a great deal of value to any answer I might get here.
Thanks again - Craig

 

[mpgmike]

I can't give you the answer for your situation, but I can tell you how I would go about finding out. I do electronics, so I have several O'scopes. I would measure the dwell output from the Pertronix unit, then measure the saturation time on the available ignition coils and match them up as close as possible. If the Pertronix dwell is too much more than the longest saturation time coil, I'd definitely use the ballast resistor.

Just as an example, the saturation time for '90s era Mopar coils is about 5.6 milliseconds, GM LS coils like about 3.6 ms, while a cheap aftermarket "performance" coil I have saturates at a mere 2.2 ms. I had the "performance" coil burn out on my '95 Jeep, which is why I did the testing. I have a couple of those cheap "performance" coils, so I could test a known good one.

 

[HALIFAXHOPS]

8 cyl pet I no ballast 1.5 ohm coil 6 cyl 3 ohm, Pet II .6 ohm coil, Pet III .3 ohm coil, hope it helps they also have their instructions online.

 

[hawkeyestoob]

8 cyl pet I no ballast 1.5 ohm coil 6 cyl 3 ohm, Pet II .6 ohm coil, Pet III .3 ohm coil, hope it helps they also have their instructions online.

Thanks for the concise and extremely helpful answer.