filter on a tachometer

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navychief
Posts: 56
Joined: Sat Jul 29, 2017 6:51 am

filter on a tachometer

Post by navychief »

I was told that I need a filter on my tach ,do to the fact that my 289 65 cyclone has an HEI distributor . The tach is original to the car. I purchased the filter through MACS. not sure how to wire it also. thank you

vicegrip
Posts: 402
Joined: Tue Jan 08, 2013 12:12 pm

Re: filter on a tachometer

Post by vicegrip »

Your tach is current driven,meaning originally hooked in series from the run position on the switch thru the resistor wire to the + side of the coil. If you are planning to hook up the tach to the tach lead on the HEI,with or without the filter,the tach won't work...and it will possibly ruin it. I don't think MSD makes an adapter for your type of tach to HEI but here's what you can try. Hook the tach in series with the start, run position on the switch and the positive term on the HEI. Don't use the tach output,filter, or the resistor wire. Some other options would be to go to a Ford Dura Spark system or the orig points and coil.

Comechero65
Posts: 1870
Joined: Wed Mar 12, 2014 10:37 pm
Location: Santa Clara, Ca

Re: filter on a tachometer

Post by Comechero65 »

I have read that the repo Sprint tachs as used in falcons and maybe comets needs a filter. They are not faria type as AFAIK. AFAIK all faria types whether falocn, comet or mustang do not need any filter.

But the faria tachs all must be connected in series with the pink (ballast) wire which is then connected directly to the ign coil or a tach adapter to provide the correct series resistance to the tach loop. I don't believe a faria tach can be connected to an HEI dist as the HEI doesn't meet the requirements for the series setup. To use the faria tach with the HEI a seperate wire needs to be run from the ign sw out to the coil bypassing the pink wire but in parallel to it. the pink wire needs to be connected to a tach adapter available from MSD that simulates a coil so the tach will function properly. Have done this so I know it works.

The MSD 8910 is the simplest and easiest tach adapter to use. Have a couple i'm no longer using.

Ron
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navychief
Posts: 56
Joined: Sat Jul 29, 2017 6:51 am

Re: filter on a tachometer

Post by navychief »

Im a little confused on this . The works fine ,seams to be accurate ,not sure why I was told that I need this filter .

Comechero65
Posts: 1870
Joined: Wed Mar 12, 2014 10:37 pm
Location: Santa Clara, Ca

Re: filter on a tachometer

Post by Comechero65 »

I'm curious is your tach a faria type or electronic type. The difference is the faria us connected in series with the pink wire and the coil. The electronic type is just connected to 12 v and ground and signal wire connected to the - side of the coil or trigger term on an electronic ign.
If you have it hooked up and it works ok don't worry about any filter. Try it first as that shouldn't harm it.
Ron
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vicegrip
Posts: 402
Joined: Tue Jan 08, 2013 12:12 pm

Re: filter on a tachometer

Post by vicegrip »

If your tach is working now,how is it hooked up? From the tach terminal on the HEI directly to input on tach? If so,tach is electronic type and most of the above info is useless....and you do need the filter. Red to tach term on HEI,yellow to tach signal input,black to a good ground. This cleans up voltage spikes which CAN cause erratic operation and tach damage.

Comechero65
Posts: 1870
Joined: Wed Mar 12, 2014 10:37 pm
Location: Santa Clara, Ca

Re: filter on a tachometer

Post by Comechero65 »

vicegrip wrote:If your tach is working now,how is it hooked up? From the tach terminal on the HEI directly to input on tach? If so,tach is electronic type and most of the above info is useless....and you do need the filter. Red to tach term on HEI,yellow to tach signal input,black to a good ground. This cleans up voltage spikes which CAN cause erratic operation and tach damage.
That's right if the tach is electronic its trigger connection would hook to the TACH connection on the HEI.
I ran a Sun tach on my motorhome which had a 454 and it simply connected to the TACH connection. Never used any filter and it worked just fine.
Ron
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popscomet
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Joined: Sat Jan 01, 2011 11:19 pm
Location: Jacksonville, Arkansas

Re: filter on a tachometer

Post by popscomet »

GOT a auto-gauge on my comet hooked to tach terminal on MSD,,WORKS perfect,no filter and has been on the comet 20 plus yrs...needle is steady and always has been...good luck.. :) :!: pop
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pop/glenda

vicegrip
Posts: 402
Joined: Tue Jan 08, 2013 12:12 pm

Re: filter on a tachometer

Post by vicegrip »

Ron,never said it definitely would cause problems, said it could cause problems. Well documented. The filter cost 30 bucks,OP has it in hand,why not use it?

Pop...apples and oranges. MSD vs gm HEI. Lot of gm cars have filters form the factory.

Stories about you guys' stuff won't mean nuthin if his tach quits working because he doesn't have a filter...just sayin

Comechero65
Posts: 1870
Joined: Wed Mar 12, 2014 10:37 pm
Location: Santa Clara, Ca

Re: filter on a tachometer

Post by Comechero65 »

Other than the repo Sprint tachs supposed to have a filter have never heard of filters being used with any tachs. Could be I just never heard about. If you install a tach and works right and is stable then no reason to add anything. Then again how do you know one is even available or even recommended for the tach you choose could be a challange. Not saying you are wrong, just never heard that.
Ron
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