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Old 08-21-2018, 07:21 PM
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fuzz fuzz is offline
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Default wiring tachometers

What I have is a SBC in my rat with an HEI distributor. I installed a digital tach in the dash and wired it to the tach connection on the distributor.. First fired the engine and the tach reads crazy, little switch on the back set to 8 cylinders. I changed positions of the switch to see if there was any change. No change so I wired another tach to the same wire. New tach doesn't read correctly either. You can see in the pictures the digital tach reads about 1300 rpm at idle and the new tach reads about 600 which I believe is correct. But as I rev the motor both tachs seem to read incorrectly. My question is do you think wiring both tachs together could cause incorrect readings? The digital tach is defective, could it be causing the other tach to read incorrectly.
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Old 08-21-2018, 10:12 PM
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Unplug the digital and try it
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Old 08-22-2018, 07:03 PM
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Dr Crankenstein Dr Crankenstein is offline
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Originally Posted by Old Iron View Post
Unplug the digital and try it
I'd do that to eliminate any interference or discrepancies between the two devices.

Just curious... what HEI do you have? GM, name brand aftermarket or E-Bay special?

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