I've had an MSD 6A in my Elcamino, then in my black Firebird, and now it's in my Nova. They all had monster tachs, so I had no worrys. But I recently bought an MSD for my Formula, and the Blaster 2 coil, installed them both today, and what a difference!! The only problem is that my factory tach isn't working correctly. The MSD manual said that I need to bypass the tach filter. I tried searching this board, and Google, but all I can find is people suggesting to buy an aftermarket tach.

I think that the filter is on the back of the instrument panel, as far as I can tell from Google searches. I'm just wondering if anyone has done this, or has had this problem and what did you do? I'm also wondering if I need to send the signal straight to the tach output of the MSD? If so, what color is the wire, and where do I find it?

Thanks for your help in advance.

 

Not every model has a tach filter.
I believe I read Camaros have them more and pre-87 year 'birds.

https://www.thirdgen.org/forums/elec...ht=tach+filter

 

When I went to the MSD 6A my tachometer would drop back to zero around 4000rpm. Installing the MSD tach filter solved the problem.

 

I forgot to mention I had a 6AL as well and the tach would just bounce.
The MSD filter worked for me too.

 

So at the end of the thread, a suggestion was made to remove the tach wire from the coil, and send it directly to the tach output from the box. He did mention that he was using the 6+, and not the 6A. I rember reading in the manual for my first 6A that the stock tach will work with out a problem, and that the Autometer's Autoguage tachs would also work, but in the new manual it says that the Autoguage won't work without the adapter (Pt #8910). And the new manual says to "bypass inline filter" for GM tachs.

Which wire is the tach wire? The white one? Also, I'm using the no splice wire harness from MSD.

 

I did that and wound up frying the tach. I never found the filter MSD said might be on my car so I went with the MSD tach adapter and all has been good ever since. I think the white wire is the tach wire but it's been so long I'm not sure. The instructions should tell.

 

I'm searching for this filter now too.


I've had a digital 6 box hooked up for a while the stock way with the white wire to the neg side of the input to the msd box. but my tach is reading higher everyday it seems like. it was ok at first but not it way off. I'm guessing I've hurt the tach which sucks. but anyways...

from what I've read, don't hook the white tach wire to the neg side of the coil, with a CD box it outputs mult sparks per plug until like 3000rpms then switches to one long fire. now mine was before the msd, so this shouldn't be what killed mine but it sounds like it sure would do some weird ****.... so the tach output on the msd is what to use. i have since switched mine and it still reads high, thats why i'm looking for this filter thing. i called msd and they told me they don't have a tach adaptor for my car and to just remove the filter.

so does anyone have a part number for the adaptor that they used and it worked? other than that I've found a wiring diagram for my 91 that says its terminal A7 on the plug that the gauge cluster plugs into.

my next step is to pull the cluster out and cut that wire and run it straight to the msd, if i don't see some kinda filter back there somewhere.

 

I'm searching for this filter now too.


I've had a digital 6 box hooked up for a while the stock way with the white wire to the neg side of the input to the msd box. but my tach is reading higher everyday it seems like. it was ok at first but not it way off. I'm guessing I've hurt the tach which sucks. but anyways...

from what I've read, don't hook the white tach wire to the neg side of the coil, with a CD box it outputs mult sparks per plug until like 3000rpms then switches to one long fire. now mine was before the msd, so this shouldn't be what killed mine but it sounds like it sure would do some weird ****.... so the tach output on the msd is what to use. i have since switched mine and it still reads high, thats why i'm looking for this filter thing. i called msd and they told me they don't have a tach adaptor for my car and to just remove the filter.

so does anyone have a part number for the adaptor that they used and it worked? other than that I've found a wiring diagram for my 91 that says its terminal A7 on the plug that the gauge cluster plugs into.

my next step is to pull the cluster out and cut that wire and run it straight to the msd, if i don't see some kinda filter back there somewhere.

 

...my factory taach displayed all these problems too. - When I put my Monster tach in you would laugh at the difference between the two, it was like the factory tach couldn't keep up with the motor. - It was probably the filter issue, but I swapped to a 96 dash, so I couldn't tell you for sure.

The factory tachs are known for being less than accurate, so I never really cared, just shift it where it feels good.

 

The tach filter is MSD 8910.