The Stovebolt Site Forums The Shop Area The Electrical Bay Ignition Coil Resistance Specs?

I'm trying to determine if my ignition coil is giving me issues. Does anyone have the primary and secondary ohm resistance specs for a 1946 216?

This morning I checked the resistance on my ignition coil with my multi-meter, and the readings were:

Primary = .13 ohms
Secondary = 14,120 ohms

Can't find any specs anywhere on the Web.

How good or bad is this ignition coil?

BTW, this is a six volt system.

Some coil specs in this HEI conversion article:

http://devestechnet.com/Home/HEIgnition

Resistance is only one consideration on coil performance, but that one looks like it's way too low. A set of points can only survive a current flow of 5 amps, maximum, and with a system voltage of 7.5 or so with the engine running and the generator charging properly, your 6V coil primary resistance should be around 1.5-2 ohms. As the primary current starts flowing, there's also something called "inductive reactance" to consider, which causes the current to slow down a little. That's impossible to measure with an ohmmeter, or other test equipment that a hobby mechanic or even a professional auto shop would have. It's something an engineer would calculate while designing the coil, and we know engineers are very intelligent people without the common sense to come in out of the rain!

I'd recommend swapping to a coil with a bit more primary resistance- - - -yours looks like it's got some windings shorted together in the primary.
Jerry

Thank you Jerry,

Any place you would recommend to order the right coil for my application? Do I specify the rating I want for primary and secondary resistance and just what should that be for both? You didn't mention where the ideal resistance should be on the secondary.

I'm thinking if I get the right coil that my performance should drastically improve. The coil that is on it now might be the original. No way of telling. It has what appears as a light tan casing.

Are the points burning out frequently? That's the classic sign of a shorted primary winding, along with a coil that's too hot to touch after a few minutes of running time. Imagine a table with four things sitting there- - - -Santa Claus, the Easter bunny, an honest politician, and a coil that will increase performance. You'll have to imagine that scenario, because they're all mythical creatures! There's a brand new Delco Remy 6 volt ignition coil on Ebay right now for $18.00- - - -buy it!

Clean, properly gapped spark plugs fire at approximately 10K volts. Once the spark is bridging the gap, it's IMPOSSIBLE for the voltage to rise any higher, so coils that can reach super-high open circuit voltages are as worthless as a screen door in a submarine, no matter how convincing the argument from someone who is going to solve all my ignition problems by selling me something might be with his sales pitch!

Rant mode off- - - -back to our regularly scheduled BS session!
Jerry

From the manual...primary resistance is from 1.28 to 1.63 ohm's. Secondary is 5600 to 9500 ohms. This covers l-4's to V-8's.
This is a cold straight resistance reading. The real current flowing through the coil is dependent on the stuff Jerry was ranting (his words) about.

beltfed,

Thanks for your input. Just what manual did you find this info? I've got the Chevy Shop Manual 1942-1948 and can't seem to locate that info in it. Looks like I'll be heading into Electrical Land and it would be great to find a good resource to help out solving electrical problems.

Got it from one of my old car manuals that cover many different cars but has sections on such things as electrical. I think the name on the cover is "Motor", but could be wrong.

Just to review, why do you believe your coil "may be giving you problems"? I think Jerry is correct in telling you to buy a new coil and give it a go.

All components in a 70 year old vehicle need to be thoroughly checked out in order to help an antique vehicle to run at its best. My coil is just one of these components that make everything work like it should. I am learning here on the Stovebolt forum, like many others, that will make these old machines run well again. I don't ever have all the answers because I never was schooled in automotive technologies. I spent most of my life in mechanical engineering mostly related to chemical industrial plants. That's why I ask for help here and over the years I've been on this site I have been awarded with awesome truthful advice to help me to save an old piece of American history which I love.

Just to be sure. To measure the primary, it is between the two terminals. To measure the secondary , it is between the positive and the center wire hole?

Since the secondary winding resistance is so high, either low voltage terminal could be used. one or two ohms of primary resistance added to thousands of ohms in the secondary isn't going to make a measureable difference. Once, long ago, the secondary winding was grounded to the coil case, until somebody figured out the battery, ignition switch, and primary wiring would make a more reliable secondary ground than a possibly loose, dirty coil bracket. Yes, the high voltage actually travels through the primary to find a complete circuit!

Something that WILL make a big difference in performance is getting the coil polarity reversed. There's something about getting the primary winding in series with the secondary that makes an engine run really lousy!
Jerry

HEY!!
As a Mechanical Engineer, I resent that remark. But I have known some that it would apply to. I've also seen some things that I've wondered what that automotive engineer was thinking when they designed it.
But you may have been talking about electrrical engineers.

My younger brother got his BSEE from Tennessee tech, and his MSEE and PHd in Plasma Physics from Rensselaer Polytech. He was one of about 5 people in the country working on the programming for the containment field for the fusion reactor until the funding dried up on that project.

Now he does computer modeling as a private consultant for the automotive industry, designing parts and running them to failure on the computer without ever physically building the parts. He bills his time out at $1,000.00 per day and he's got people waiting in line to hire him.

He still calls me for engine-building advice!

A civil engineer must have designed the female body. Who else would have put the playground next to the toxic waste dump?
Jerry

Jerry, Your brother and a number of engineers figured out...Its really hard to keep some things bottled up. Plasma is one of them. I spent time at the "Magic Donut" at the Y-12 facility in Oak Ridge, TN. I afraid tis not yet time for man to burn water as a fuel.

Speaking of coils...
As a young man, I had a landlord who urged me to look into engineering as a college major every time I saw him. He said, "It pays well, and you don't need to know anything, and you don't get dirty."
Carl