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Old 04-29-2021, 01:50 PM
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Default 1964 tach inline filter

Just installed an MSD. As described in the instructions, my tach stopped working. the solution in the instructions is to bypass the inline tach filter. For a 1964 A body - does anyone know where that lives and/or what it looks like?

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Old 04-30-2021, 04:45 AM
Geoff Geoff is offline
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An MSD what? Box, dist?

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Old 04-30-2021, 08:10 AM
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Sorry, yes it’s a 6al digital box. Distributor is stock with Petronix. Everything works fine. The tach issue is called out in the 6al box installation, and the remedy is to bypass the inline filter but I don’t know where/what that is...

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Old 04-30-2021, 08:57 AM
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The tach should connect to the MSD box and not the distributor.
The MSD doesn't provide a correct 'signal' for the older tachs.
Not sure what the inline filter means?
Usually the MSD has its own Tach connection?
(never used a digital MSD though)



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Old 04-30-2021, 09:11 AM
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Does it have a wiring diagram with it?
Looked like a grey wire is for the tach output?



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Old 04-30-2021, 09:20 AM
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Thanks John. I think I have the set up right - I did connect the tach wire to the msd box. pretty much followed the diagram I included here. And then also the tach section of the doc. most applications with this issue have a tach adapter that you can use - but for GM, you are supposed to bypass the inline filter if the issue comes up... (they suggest elsewhere in the doc that it does not always come up as an issue)
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Old 05-01-2021, 03:14 AM
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MSD made two tach adapters, #8910 & #8920. I think you might need the 8920.

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Old 05-01-2021, 12:11 PM
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I’ll call msd next week and see what they say. That table in my pic was not totally helpful to gm...

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Old 05-06-2021, 11:49 PM
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I wanted to close this one out- the 8920 adapter from msd fixed it. Tach working again....

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