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Old 11-25-2016, 02:47 PM   #9
MikeB
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Join Date: Jul 2000
Location: North Texas
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Re: (Question) HEI Internal to external Coil Conversion

The tach connection is on the negative side of coil primary winding on both internal and external coils. What you have there is a pulse generated by the HEI module.

Also if you do convert to external coil, you do NOT want or need a ballast resistor. Its purpose is to reduce current through the ignition wire and points.
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Mike
1969 C10 LWB -- owned for 34 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes.
1982 C10 SWB -- sold
1981 C10 Silverado LWB -- sold, but wish I still had it!
1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming.
Retired as a factory automation products salesman.
Worked part-time over the years for an engine builder and a classic car repair shop.
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