Bouncing tach

[caltanian]

Yes. I know that there are many threads about this. They all seem to say multiple things however, and i figure might as well get it straight.

I have a pertronix installed, and a 3 ohm coil. Bypassed resistor, the car runs great, pulls hard, yada yada. My tach however, starts to bounce around 3500rpm. If i stay in a slow acceleration, it seems to track for a while longer, but then bounces, and with WOT, it just bounces around between 2500 and 5500.

I have heard go back to points. I have heard get a new tach.

What does one really need to do to fix this?

[Zed Head]

You didn't say if you've ever seen it work right or it's always been this way. But, the cheap way to choose between points and tach is to just re-install the points (there's a whole range of points for sale between $1 and $2 on RockAuto.com). If the problem goes away then you can focus on making the "good" tach work with Pertronix. If the problem stays, the tach is probably bad.

[caltanian]

You didn't say if you've ever seen it work right or it's always been this way. But, the cheap way to choose between points and tach is to just re-install the points (there's a whole range of points for sale between $1 and $2 on RockAuto.com). If the problem goes away then you can focus on making the "good" tach work with Pertronix. If the problem stays, the tach is probably bad.

Never did work properly for me. Pertronix was always there, and got tuned up by a good shop early on for me.