Tach Filter????

[byates2]

So ive seen that i need a tach filter because i am running an HEI on an old style tach. I'm trying to figure out how to wire it on. Amyone know??

I'm guessing the blue wire goes into the pink clip, but where do the tach filter wires go??

[JimKshortstep4x4]

Is your tach an original or is it a repop?

Jim

[byates2]

Its a repro
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[byates2]

Can anyone help me?? Do the reproductions need the tach filter. I have HEI. Since i dont have a coil, where would the wire that needs to hook up to the negative side of the coil go?????

[Husker]

I would not think you would need one.
Ron

[jocko]

My gut feeling is that you do need one (tach filter) - then I found this on a chevelle forum I was looking at on this subj and it seems to back up that feeling (the poster at least "sounds" like he knows what he's talkin about... )

"You need to install a tach filter between the tach wire and the distributor. The waves that an HEI distributor puts out cannot be properly read by MOST analog factory tachs. I have heard (but never personally seen) of very few instances where a tach worked without any modification. Anytime someone buys a harness from us that is modified for HEI, we typically inform them that they will need to put a tach filter in line on that wire. Accell and Mallory both make a piece, but most any Camaro or Monte Carlo or other HEI vehicles from the 70's/80's will have a tach filter on them if they are equippped with a factory tach. A junk yard trip is possibly in order. They look like a condenser with wires coming out of each end....1 to the coil/distributor cap, the other to the tach wire. They are a plug and play deal. They show up on ebay pretty regularly and can usually be bought for 35-50 bucks. Good luck"

Here's the link to the whole discussion http://www.chevelles.com/forums/showthread.php?t=312599

As for the wiring - I am reasonably sure that the tach filter (Classic Truck Parts sells them: Part #24-736 $26.95, but you obviously already have one in th epic there) simply fits inline at the three connection points shown in the wiring diagram - I think.

The pink wire and terminal you show in your picture is a piggyback - i.e. a means of plugging into a power lead on your fuze box without losing the current purpose of the connection (i.e. 2 wires (one for your tach, and one for something else that is already there) into one hot connection). So, without seeing the whole wiring setup you have (and had), I'm not real sure about what that particular wire is used for. Sorry - not a lot of help on the wiring part of your question - but I am pretty sure you need a filter.

[Photoferg]

This post is over a year old? I am faced with same question today. I did not see an answer to original question? Any help?

[MARKDTN]

Looks like:
red to coil, there is a tach post on an HEI to put it on
yellow to tach
black to ground

I have always used them (not on a truck though), but I have never seen a 3-wire. The stock ones on later GM cars are just 2 wires.

[cleszkie]

I ran my repop tach off my HEI for years with no issues. Now I run it off my MSD 6AL ignition with no issues. Never used a filter.