What is this piece?

[NVvetgirl]

I have a small electronic piece of plastic bolted to the intake maniford behind the carb. It has a short piece of wire (4") on each end with connectors. Obviously it is supposed to connect to something (that was probably removed years ago) but neither end is connected to anything. It is just sitting there. Any ideas on what it is supposed to be? confused

 

[bill81vette]

would you post a pic,please????

 

[76okievette]

Sounds like the tach filter on my car but with out a pic can't be 100%.

 

[KANE]

Sounds like the tach filter on my car but with out a pic can't be 100%.

I agree. Not much else fits that description. Tach filter is correct for that year with HEI.

 

[wishuwerehere82]

Does it look like this?

 

[NVvetgirl]

What is tis piece?

You must be a mind reader. That picture is exactly what it looks like, except mine is much older and dirtier. What should I do with it since it isn't hooked to anything? Thanks for the picture.

 

[bmotojoe]

On the drivers side of your distributor cap there is a section of the cap where the plastic is molded out. If you look at that part real close you will see two sets of lettering. One side will say BATT and have a red wire plugged into the bottom side of the molded part and the other side will say TACK, I believe as your looking at it from the driver’s side it will be on the left side. Look at the connector on the BATT side (red wire) and the same looking end connector on the tack filter will plug into the distributor cap where it says TACK the other end will connect to a brown wire with a plastic connector on it.
If you look at the picture above and yours has two connectors real close to each other don’t worry about that second connector off the short pig tail. The picture above is a replacement part for mid to late 70’s cars and it is not used. If yours has only one connector at each end then it is the original tack filter.
Brian

 

[wishuwerehere82]

You must be a mind reader. That picture is exactly what it looks like, except mine is much older and dirtier. What should I do with it since it isn't hooked to anything? Thanks for the picture.

Most of them are older and dirtier than that one.
I guess the first question I would ask is why isn't it connected?
My guess would be that either it is shorted and doesnt work, or that somebody decided it isn't neccessary for operation.
What it does is to smooth out the tach signal so that the tach needle doesn't pulse abd stays steady.
You could try plugging one end of it in to the Tach connector on the distributor, and the other end into the wiring harness connector that is plugged into the Tach connector now.
If it works, great!
If the engine stalls, not great!
If it's not neccessary for the Tach to work, just loosen the bolt and pull it off. Then tighten the bolt back to torque spec. But my suspicion is that the Tach needle is wiggling back and forth without it in the circuit.
You can save it in the jack box for posterity.

 

[Nobody Cares]

Thats the pix of the tach filter off my 80. It is shorted out in the filter itself. Just as the previous thread stated if shorted out the car will stall. Just ordered a replacement fron Rodney Dickman. Dave

 

[76okievette]

I just had a flash and wanted some inputs.
After reading all these posts about the tach filter it got me thinking. Here is the situation, I replaced my distrubtor and tach filter when I removed my intake manifold a month ago, go it all back together and everthing worked fine but after about 3 weeks the tach stopped working so I figured since the filter and dist were new that it must be the tack circuit board and since that is so hard to replace I was just waiting until the next time I removed the dash. Now I am thinking I could just take the filter out of the circuit and wire the tach direct to the dist and if it worked, even if it was bounching around a little then my circuit board was ok and it was just a bad filter. Think this will work?

 

[bmotojoe]

Personally I wouldn’t make a direct connection between the distributor and the tachometer brown wire. If for any reason this circuit gets grounded permanent damage can occur to the HEI module and the ignition coil and could possibly burn out your circuitry in the tachometer itself. When you removed your intake manifold, was part of the project to clean and paint it? If so you should remove any paint where the bracket of the tachometer filter comes in contact with the manifold. Yes the tachometer filter has to be grounded properly to function. This is the reason a car stalls if the tachometer filter internally shorts out, it grounds the coil and HEI module.
Brian

 

[76okievette]

Brian, thanks and yes I did paint the intake and no I did not clean off the pain where the filter bolts I will do that first and see what happens. Thanks for the input.

 

[minifridge1138]

I have some problems with my tachometer.
When I start the car, the tach starts at 0 and slowly climbs past the red and maxes out. The needle just stays there.
It does this whether or not I have the brown(?) wire from the tach connected to the distributor.
Could it be a dirty contact on the circuit?