5th gen tach inaccurate

Redster · Posted: Sun Oct 12, 2008 8:48 pm Post subject: 5th gen tach inaccurate

I just finished putting a 2000 vortec with an HEI in my 79 but the tach is off. It reads high (compared to my electronic timing light which has always proven to be spot on). At about 850 the car tach reads about 1150, and at 2250 reads about 3000. I see that there is some kind of 'can' looking device on the firewall which I was told that some of the older cars used a resistor. but the whole thing doesn't make sense to me as it seems it should be off by 1/2 and not a variable amount. It has been consistent though. any experience and help is greatly appreciated.
Thanx Cool

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the RED one
You can talk about it all you want .... but you will never really know 'til you go

87ElCamino · Posted: Sun Oct 12, 2008 9:25 pm Post subject:

That "can" is the tachometer filter. Try jumping it out to see it the tachometer reads correctly
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Ernie
87 El Camino
Rolling Eyes

"To be Old and Wise, you must first be Young and Stupid"

greywolf · Posted: Tue Oct 14, 2008 9:54 pm Post subject:

Right -- my tach works better without the filter.