Ballast resistors

D

danford1

New member
I need a ballast resistor between 1.6 ohm and 2.0 ohms.
I see moroso makes one that is 1.82 ohms, perfect... It is part number 72390. But I have to mail order it which adds shipping.
I also found some wells resistors I can get locally at auto parts stores. Number cr107 and cr139. I can't find anywhere listed how many ohms these are.
Does anyone here know what resistance the cr107 and cr139
parts are?
I know I can take my ohm meter to the auto parts store but the car I would drive there only gets 10 mpg and I can't afford the gas just to be curios. It is a long way from me.
If I knew for sure what the ohms were, then I would drive there and get it. Make sense?



Danford1
 
The wells site says the cr107 is 1.125-1.375 ohms, but they provide no info on the cr139. Not much help.

You might try emailing the Jeff here on this site and see if he has what you need in stock. Not as quick as driving, but you will get the correct part.

Lyle
 
We've posted about ballast resistors many times here in the ignition tech sub-forum, do a search and you will see a wealth of information.

I keep on hand in my shop a standard motor products ru10 for the application you describe. For a v8 breaker point ignition when used with a coil with a primary resistance of 1.4>1.8ohms, that is a perfect match of coil saturation/breaker point current draw vs. Breaker point service life. A wells cr 107 works just fine also, it's well withing the tolerance band for a v8 breaker point distributor if used with a proper match coil.

A wells cr139 is rated at a nominal 0.8 ohms, way too low to use with a v8 coil application, but perfect for a 4 cylinder ignition as long as a coil with a 3.0 ohm primary resistance is used. I also sometimes use two wells cr 139 resistors wired in series for use with a v8 distributor.

In this pic you see my "electrical system in a box" as described in this thread:

http://www.forums.IHPartsAmerica.com/electrical-tech/1843-electrical-system-box.html

The various ballast resistors that are mounted can be configured to provide various values depending on whether I'm going to install it on a four, six, or eight cylinder engine. Those are all various wells part numbers though brand name doesn't matter at all, only the value of the resistor.
 

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Re: Ballast resistors, which one do I need?

Yes search will bring up a lot of info, to much sometimes...

I have a msd blaster 3 coil. It measures 0.9 ohms primary resistance.
The old Ford yellow top coil measures 1.7 ohms. The old coil works as is with no resistor. I let it idle for over an hour, no problem.
The old coil is .... Old....

I want to use the new msd coil. Am I correct in assuming a 0.8 ohm resistor is the one I need?

If not, how can I best match the resistor needed to what I have?
(GM 4 pin ignition module, Ford duraspark distributor with blaster 3 coil)

thanks.
Danford1
 
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The old coil is...still working just fine. The engine doesn't care. It's old too. Even if the newer coil has more potential energy to deliver, the engine can only make use of so much. But yes, if you're set on putting the one with all the shiny decals in play, you'll need a ballast that will give you the same total resistance factor.
 
As always, the best answer for stuff like this lies in the details.

You haven't given us the big picture. Don't even know what engine or distributor you are working with.

With a mongrel ignition system like you kinda describe, all bets are off.

At this point...I "assume" you have mated a Ford duraspark magnetic tigger into some kind of non-oem distributor and need the delco hei module to serve as the interface "amplifier" to fire some kind of unknown "Ford" coil with a non-stated primary resistance factor???...and then want to run an aftermarket msd blaster 3, ultra-low primary resistance coil with that setup?? I'd highly recommend to forget that coil!

Low resistance coils should only be used with appropriate capacitive discharge add-on boxes such as the "6 series" stuff from msd, mallory, accel, crane, etc. Fuckin' with a "ballast resistor" does not make for a proper match when doing this, no matter what the marketing smokeblow alludes to.

A duraspark mag trigger can signal an msd box directly, no need to fuck with a delco amplifier (module). Ya simply wire in the cd box using the mag trigger input.

A delco amplifier alone can't use a low resistance coil! It'll cook it. There are some aftermarket delco-type amplifier/modules available that can match witha low resistance coil but they are spendy and they are still only an inductive ignition system, the cd system conversion is far superior to any inductive ignition setup.

The blaster 3 coil does have a significant turn ratio upgrade that when combined with the low resistance primary winding can produce a major open circuit voltage increase which the typical engine can never utilize. Those coils are the typical oil-filled "canister" style and are considered old technology compared to the more appropriate "e-core" coils that are epoxy or urethane potted.

More information regarding performance ignitions systems is contained in this thread:

http://www.forums.IHPartsAmerica.com/ignition-tech/644-ignition-system-performance-upgrades.html

Here at ihon, we are continuing development of a magnetic trigger distributor "set" that can work in stand-alone mode, trigger a cd box, and or be used with a multi-pin delco module to allow interface with the typical GM-based efi conversions based upon customer requirements. They will also be easily "convertible" if in the future a customer decides to move into the efi arena without having to obtain a different distributor. These will be for ihc-based production engine applications only.
 
Since there is no refund on electrical parts and the customer just bought the msd coil, I'm going to make the shiny one with a decal work.
Yes the car runs with the old coil which has about 0.8 ohms more primary resistance than the msd.
Before I just buy a 0.8 ohm resistor I want to know how to determine the optimum size. How can I calculate or measure the needed resistance?
This GM 4 pin ignition module is real finicky on ignition coil resistance, to many ohms, it doesn't run, to few it doesn't run. I have something that works but I don't have any way of finding the run not run limits. I want to be dead in the middle but don't know how to get there.

To answer what engine this is it is a freshly rebuilt Ford 302. It has a re-manufactured duraspark distributor and the 4 pin delco brand ignition module number d1906 with the mentioned msd blaster 3 coil. The Ford distributor and GM module are known as "the poor mans" electronic ignition because everything together is less than a msd box...

Another note is this isn't my car. I'm working within a tight budget of the owner. He just bought the coil and $160 for a msd box is out of the question.

The reason for the old Ford coil is because it is something I tried and worked. I also tried a new Ford tfi coil, didn't work, my guess it it needed a ballast resistor. I tried a jegs regular cheap chrome coil, same thing. It is clear this set up needs a ballast resistor I just don't have a clue how to determine the correct one. Hence me coming here to the experts.
Thanks
danford1
 
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Obviously you have just been throwing parts at this mongrel without doing the research regarding parts matching. Anyone can do the research online regarding any coil (oem or aftermarket) or any other ignition system component specification, just like I can.

I don't need to be lectured about "poor man's" electronic ignition, I've been doing this shit for over 50 years and know what works and what doesn't regarding this mongrel ignition schnizz. The owner should have done some proper research before springing for totally unsuitable parts (the coil), this ignition stuff is far from being rocket science.

What the hell is a "Ford" coil??? Couldn't be more than 50 or so "Ford coils" spec'd out on various fomoco vehicles since 1908. No doubt a "cheap chrome coil" won't work at all, how the hell do ya know what the primary resistance is for proper matching to the rest of the system?

We don't "guess" at what works here in our company and on this forum,...we do the research, we have the experience in doing this type work regarding ihc-produced products, and knowledge base to know what works and what doesn't. I do these magnetic trigger distributor conversions all the time using either Ford duraspark mag trigger sets, or in many cases, the superior chrysler mag trigger set. Either one is dirt cheap.

If using a delco hei module, the proper matching primary resistance of a oem/aftermarket hei "in cap" coil is 0.3>0.5 ohms. And an hei distributor either oem or any of the myriad aftermarket clones, do not use any form of a ballast resistor. Why would you add a resistor to the mix????
 
Thank you for the fast reply and info.
The reason I used a resistor is to get it to run. With no resistor it would start but not idle. If I put in an ignition resistor (tried a 1.5 ohm one) it will run with the msd coil.
If the oem coil in cap has 0.3-0.5 ohms, then why wouldn't the msd coil with 0.9 ohms work?
If I swap in my 1970's Ford yellow top coil which has 1.7 ohms primary resistance, with no ballast , it runs fine.
I'll have access to a msd 0.8 phm resistor in a couple days. That with the 0.9 msd ohm coil would equal 1.7 ohms which is what the Ford coil is. Perhaps I'm missing something. Please help me out of the run no run situation. I need to get this car done and out of my garage. I want it to be reliable for many years so I don't see it again.
With what I have to work with, what is the best way for me to go? Get a different coil or get a ignition box ?
Would a 3.0 ohm pertronix coil work (either part number 40511 or 40611) ?
Or
would I be better of swapping out the GM hei module and going with a Ford ignition module? I saw one on rock auto, old duraspak II , here is a link http://www.rockauto.com/catalog/moreinfo.php?pk=49685 .
if I went with the Ford module , what coil would I use ? would the blaster 3 work ?

thanks again .
danford1
 
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If I went with the Ford module , what coil would I use? Would the Blaster 3 work?

If I went with the Ford duraspark ignition module , what coil would I use? Would the blaster 3 work?

Danford1

danford1 said:
thank you for the fast reply and info.
The reason I used a resistor is to get it to run. With no resistor it would start but not idle. If I put in an ignition resistor (tried a 1.5 ohm one) it will run with the msd coil.
If the oem coil in cap has 0.3-0.5 ohms, then why wouldn't the msd coil with 0.9 ohms work?
If I swap in my 1970's Ford yellow top coil which has 1.7 ohms primary resistance, with no ballast , it runs fine.
I'll have access to a msd 0.8 phm resistor in a couple days. That with the 0.9 msd ohm coil would equal 1.7 ohms which is what the Ford coil is. Perhaps I'm missing something. Please help me out of the run no run situation. I need to get this car done and out of my garage. I want it to be reliable for many years so I don't see it again.
With what I have to work with, what is the best way for me to go? Get a different coil or get a ignition box ?
Would a 3.0 ohm pertronix coil work (either part number 40511 or 40611) ?
Or
would I be better of swapping out the GM hei module and going with a Ford ignition module? I saw one on rock auto, old duraspak II , here is a link more information for standard motor products lx203x .
if I went with the Ford module , what coil would I use ? would the blaster 3 work ?

thanks again .
danford1
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