I installed an OER tach into my 68. I am running the MSD ignition system so I installed the "Tach Filter." The tach is still not working right. It works until it hits about 1800 RPM and then it sticks. If I tap the tach with my hand it lets go and falls back to the idle RPM. It never goes above the 1800 mark. What else is it? Could it be the tach is just bad? Did I do the wiring of the Tach filter wrong? I followed the directions to a "T." I just don't get it. Any feedback/suggestions would be helpful. Thanks.

Why do you need a tach filter with an OER tach. I thought the filter was just for HEI applications going to an original tach. I might be wrong since I 'm more familiar with the 69. I would say if it sticks at 1800 rpm every time, it a bad tach. Are you taking the tach signal off the box or the coil?

I needed a tach filter with my msd 8361.

I made my own. While doing so I discovered that if the resister value is too large compared to the capacitor valur, the tach will behave exactly as you described. I ended up with a 1 microfard cap and a 470 ohm resister.

In one of my tests, with a 10k resister, the tach needle would fall to zero just above idle. Another, with a 1k resister, it happened at 4500 rpm.

"While doing so I discovered that if the resister value is too large compared to the capacitor valur, the tach will behave exactly as you described. I ended up with a 1 microfard cap and a 470 ohm resister."

I have no idea what this means.....lol. What do I need to do.....keep in mind though I am not familar with building anything with electronics.