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Old 03-09-2010, 04:24 PM
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Tach reading 500 RPM or so lower than actual

So i have a Mallory ignition box, dist, and an autometer 5" tach. When i first fire up the motor it will read a correct RPM for a few moments then drop 500 RPM. My timing light shows the correct RPM which is about 500 RPM higher than what my tach is showing. So at idle its reading 400rpm when its really 900.
I have New coil, new cap, new rotor, new ignition module why the odd job jumping around on my tach? Could it be the mallory box? Its a hyfire VII's.

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Old 03-09-2010, 07:59 PM
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How new of design is the Autometer tach?

A buddy had a Autometer tach that was off.. turned out the programing in the tach was not correct. Autometer tech walked him through the re-program procedure on the phone
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