Tach Filter

[mrvette]

I have never bothered to see any GM reference to that tach filter...

it does serve a dual purpose in that position though....one is to reduce the antenna/broadcast effects of the spark signal to AM radio....primarily...second is to filter the HEI signal to the tach....like I said before, it's done at the tach in most aftermarket applications....
but a old shark electronic tach needs that filter there or the signal is all over the map....

:shocking:

 

[big2bird]

I have never bothered to see any GM reference to that tach filter...

it does serve a dual purpose in that position though....one is to reduce the antenna/broadcast effects of the spark signal to AM radio....primarily...second is to filter the HEI signal to the tach....like I said before, it's done at the tach in most aftermarket applications....
but a old shark electronic tach needs that filter there or the signal is all over the map....

:shocking:

Yep. Roger, read the bottom left corner from the 81 Shop manual.

 

[big2bird]

Why ? In the GM manual the picture of what WE are referring to as the "tach filter" is actual called the "radio noise capacitor" , same as what is in the drawing above.Here is the matching page for the diagram.

Roger. Take one apart. It's an "RC" circuit. It's NOT just a cap. It's a "filter."

 

[js292]

Just to clairfy this is for my 85 not my 71.