Ignition: Ballast resistor

[Felix]

I'm aware this topic has been discussed before but not like this.

I'm at a standstill with my ignition because I can't find the specs I need and so can't make sense of which one to use.

Regardless of what car or application. I'm hunting for parts no longer available so matching specs is the best I can do. What is holding me up is an understanding of the ohms ratings of the ballast/ignition resistors. Some are rated at 0.4, 0.6, 0.8 ohm and others at 1.6, 1.8 ohms etc... Others say they are variable 0.75-1.5 ohms. Not many, and I mean none I can find, give a cold and hot value and watts ratting like the Mallory 700 I'm trying to replace. As all of my ignition is Mallory I have been advised not to mix and match. Best to stay within the parameters set by the manufacturer and hopefully no electrical glitches will result.

Coils are of the two main types internally wound to give 1.5 ohms or 0.6 ohms or there abouts. My coil Mallory 29150, high output low resistance coil in the 0.6 ohm range. is approved by Mallory to use with all of there ignition systems, from points, points replacements to transistorized and CD ignitions. It is not internally wound to give the 1.5 resistance to negate the use of a ballast resistor so it is recommended to use the Mallory 700, with 0.75-1.5 ohm variable resistance.

I believe I need a 3.0 ohm resistance system to run the engine properly on points or optical trigger.

Holley/MSD want to sell the MSD 8214 resistor as a replacement but where are the specs? 0.8 ohm is all that is mentioned. Apart from it being recommended to use with there Blaster 0.6 ohm coils. Others just give one value. Is that hot or cold?

I have read that I could use any but that doesn't seems right. If I could use any then why so many different numbers?

The system:

Running in a 59 Lark with no resistance wire.

Delco window style distributor with Mallory e-spark points replacement.
Mallory 29150 electronic coil.
Mallory 28371 circuit guard module.

Just need the ballast resistor. A Mallory 700 or equivalent.

Any help or education would be appreciated. Please, I need some numbers or a detailed explanation as to why I shouldn't care?

Thanks.



P.S. If you want to know how I ran it before I had a Mallory 6AL hooked up and therefore did not require a ballast resistor. Now I do.

[gordr]

Well, according to Ohm's Law, if you ran an 0.6 Ohm coil with no ballast resistor on a 12 volt system, the coil would pull 20 amps with the points closed. That would be hard on the points, and also the coil. I think your suggestion of 3 Ohms is about right; that would give about 3 amps primary current, and the 3 Ohm resistor would have to be able to dissipate 27 watts.

[Dwain G.]

https://www.summitracing.com/parts/MAA-700

[Felix]

https://www.summitracing.com/parts/MAA-700

Dwain, call me a little skeptical, as I have known of that item for a while and the quality displayed in the images does not justify the price, and at about $44-45 once it gets to me, unless I buy quite a lot form them to get free shipping, it is last on the list. A list of 1.

What I was really asking was not where to get one, although if a Mallory was obtainable I take it, but how to know the specs on all the others that only give one number and don't mention whether that is hot or cold and all those other specs. Most of all once all, or as many as needed, specs are known a proper comparison can be made. If then it makes no difference then it's done. If it does make a difference, which resistor to use, with the system I have, then at least I have some idea which one to use.

Gord, as you can see once one plugs the numbers in the answer is clear. but, getting the numbers to plug in and knowing if they are using the same standards is the hard part. I've been looking for a few weeks online and in some books I have and so far, unless it's the same part as Dwain G mentioned. That's the reason for the questions. If one company is so specific about using a part and that part has specs that can't be found on other parts it makes it hard for me to see how to know without actually testing the ohms hot and cold.

It's not like I don't have any numbers to work with I just don't know how the manufacturer came to that number. What international standard did they work to? If it is Ohm's law only and the manufacture does their part then a resistance value is given to the product. Some resistors have a value stamped into the metal bracket, 0.4 for example. What I don't know is why are there so many different numbers if it doesn't make a difference? Does having the wrong value resistor lead to short lived pointless conversions? Does the current resistance value of the in-loom Studebaker ignition resistor, of the last years, need to be check and a new wire run? Have we been destroying distributor modules from wrong ballast resistors?

As it maybe in this case I don't know enough to know I don't know anything. Going by that I don't know anything at all. Sounds about right.

[jackb]

I recently bought a 60's Chrysler ballast resistor and measured 1.5 ohms resistance. So far the engine runs fine.

[Flashback]

Standard Motors Products RU-13T

[gordr]

Felix, I was basing my remarks on it being used with points, no module. Once you get into solid-state modules, triggered by points or otherwise, then it's the module manufacturer's call what ballast resistor to use, if any. GM's HEI don't use one.

[Felix]

Felix, I was basing my remarks on it being used with points, no module. Once you get into solid-state modules, triggered by points or otherwise, then it's the module manufacturer's call what ballast resistor to use, if any. GM's HEI don't use one.

Yes, that's where I find myself. Shelves with Mallory ignition stuff but no #700 resistors, as recommended by Mallory for all Unilite, e-spark triggers, as I had not planned to run the system without a CDI box.

[Felix]

I recently bought a 60's Chrysler ballast resistor and measured 1.5 ohms resistance. So far the engine runs fine.

Was that your readings or stamped on the unit? If you measured it with a ohmmeter did you zero it or subtract the meter's probes resistance? I'm wanting to know if you were told that, read that, or tested that? Also, if it matches the documented number?

[Felix]

Standard Motors Products RU-13T

I'm aware they exist. What are the documented numbers? Have you tested it and confirmed the values? It may work well for it's originally designed purpose, probably a points triggered distributor, but will it be the best option for for the optical trigger?

I'm not saying this wont work. I don't know. What I do know is that owners of these Mallory based systems have found over the years that Mallory made the units to work in conjunction with other Mallory components and live longer lives if done so. My system calls for a resistor with particular values and I am trying to stay as close to that as I can, given the #700 is no longer available.

Many components can work, and do work, if not exactly matched to the original design. In this case the life expectancy can suffer if not matched well enough. Some ignition systems one may never notice. Electronics have a tendency to heat up and blow out if grounding, resistance, spikes, etc... are left uncontrolled. I would like to be more in control.

I would like to use that unit as they are plentiful, cheap and would probably work well if my car was in stock form. Hopefully it has the specs needed.

[Dwain G.]

Have you checked this........scroll down til you find #700.

https://documents.holley.com/mallory-msd_crossref.pdf

[gordr]

8214 (MSD) 0.7 to 1.5 ohm. Probably those are the "cold" and "hot" resistance values. That is the function of "ballast" resistors: to limit current by heating up and increasing their resistance. Which is why they are typically made of porcelain.

[Felix]

Have you checked this........scroll down til you find #700.

https://documents.holley.com/mallory-msd_crossref.pdf

Yes, many times and also the chart that shows what coil works with what ignition box.

When you see the MSD resistor, and I have one right in front of me, it has 0.8 ohms on it so it maybe MSDs only part that is close to a direct replacement, but is it the same throughout the range of the Mallory? MSD doesn't post the specs so I have to question it's values.

[Felix]

8214 (MSD) 0.7 to 1.5 ohm. Probably those are the "cold" and "hot" resistance values. That is the function of "ballast" resistors: to limit current by heating up and increasing their resistance. Which is why they are typically made of porcelain.

The 8214 (MSD) 0.7 to 1.5 ohm.? Where did you find those specs?

[Felix]

Anyone have old catalogs with info like this