Don Terrill’s Speed-Talk

I have an MSD coil model 8207 SS series. When I test it with my ohm meter I do not get the factory specs of: .355 ohms for primary, 4.40k ohms for secondary.

What I get is .5 ohms for primary, 2.8k ohms for secondary. Is this normal or is the coil going bad or is bad?

I did email MSD. They finally responded with "low on the secondary but the coil should still spark." I then asked will I get the performance benefits? I do go to the track and race this car. They responded with "then I would replace the coil just incase it starts to misfire when it gets hot."

I did call Holley prior to receiving the above response since it was a couple of weeks of waiting. They told me the spec is measured under a load so I would not be able to duplicate with an ohm meter. I'm not an expert but to me resistance is resistance and not really buying it.

What do you all say???? I'm running coil via 6AL.

Most DVMs are not that accurate below 1 ohm. Also, digital meters can give 'strange' readings on the sec winding. I wouldn't worry about it, use the coil.
I have a special low resistance ohm meter for measuring less than 1 ohm.

Will do and thanks for the reply. I guess I was more concerned about the secondary.

Is the secondary resistance the same on positive and negative?

If I remember correctly it was. Is that a good thing? lol I really don't know.

The manufacturer should specify the internal temperature of the coil at which the resistance was specified. I’ve seen secondary resistance go up by 50% from 15 deg C to 100 deg C. And some coils like LS ones for example have a diode in series with the secondary winding so any resistance measurement will be meaningless. For example just now I put a diode in line with an ordinary coil and without the diode it measure 7000 ohms both directions and with the diode it measure 4.2 megohms one direction and completely open circuit the other direction.

Thanks...you guys are awesome. Great info from all.