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I have a 454 in a 71 Chevelle running a Mallory Unilite and an old style (12+ yrs) Jacob Electronics mileage master ignition and their high energy coil. I ran this on a small block (about 10 years ago) with no problems. Now years later, I finally have it running again but with the BBC. However, the tach will jump all over the place including to 0 and back up to the actual RPM. Eventually it will die and not spark for a while (several minutes), and then will restart. I by passed the Jacob system to an Accel coil and the Unilite, but it still happens.

I've searched this entire forum for ballast resistor questions and thank you all for information I was able to gain. However, I'm still a little confused :confused: I checked the coil + voltage with the engine running as explained and it only registers about 6.8 volts. There is a ballast resistor on the fire wall, I suppose I need to disect the loom to see what previous owners have done. Maybe the original restitor wire is still there also??? which might explain the 6.8 volts. Any other ideas? And thanks again for all the information from your archives.

Tim McNaught
 

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Maybe just look at the wire on the opposite side of the ballast resistor. That would be the wire on the ballast resistor to the firewall. If it has a cloth-like covering on it, it's resistor wire.
You also might measure that point to ground. A regular copper wire will read 12+ volts. Very close to the same reading you will get on the IGN terminal in the fuseblock.
 

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I'm not familiar with the Jacobs ingnition box but the Mallory Hyfire VI-AL has a wire dedicated to the tach, and the instructions note that an adapter will still be needed for some tachs. I suspect any multi strike ignition wold have to have a tach wire and not be connected to the distributor.

Are you using the same tach you had before?
 

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Discussion Starter #4
I'm not using the same tach. However, it did this strange thing even before I hooked up the tach. It was just easier to see with the tach hooked up. Part of my concern is whether or not the 6.8 volts is enough. It seems the recommended voltage for non-HEI is 9 volts. I was also wondering if maybe the ballast resistor (of unknown origin) may be dropping the voltage too much. Replacing it with the appropriate NAPA item described in previous posts will probably be me next step. Thanks,
Tim
 

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Discussion Starter #5
Okay, I checked the fusebox side of the ballast resistor with the engine running and it was about 9-9.4 volts. The distributor side of the ballast resistor was about 6.5 volts. Looking at the wire on the fusebox side of the resistor, it looks silver, not copper. Hence, I'm guessing a previous owner hooked the resistor wire to a ballast resistor. Does this sound logical? I believe my best alternative, since the resistor wire has been altered, would be to run a fresh wire from the fusebox to the ballast resistor. Opinions????
Thanks,
Tim
 
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