How did you attach the 8920? I ignored the instruction and hooked it up initially 'in-line' with the old tach wiring and the tach wouldn't even work - Ground to ground, ignition to ignition, trigger to trigger, violet unplugged. I haven't had time to try the instruction route.I had the exact same situation.... plus ... as the engine RPMs increased, the tach needle increased disproportionately.... It was way outa wack... I installed the 8920 tach filter. Its better than it was... Close at idle but it is still off by about 500 RPMS at 70mph. VERY irratating situation. I hope you have better luck with it than I did....
Thanks for that! Any idea what he did?I had the same issue. I changed out the fuel gauge for the tach and it was way off. The guy that installed it finally adjusted something behind the gauge(think he said he had to break a solder) to make the adjustment and ever since i have been within ~100rpm of my digital tach readout on my shiftlight.
Well I have my 69 Tach out of the dash at the moment. I think it is the one or both of the green circuits shown here. They are attached to a white circuit board that connects to the three lugs on the rear of the tach. I don't know if 68 Tic-Toc-Tach has the same guts. I think the wire color is brown going to the coil.OK..according to the URL that Steiner posted, GM TACHs have an inline filter that has to be bypassed.. Any idea where this filter would be physically located?
I have a TIC-TOC in my car and I am thinking of getting an MSD system. My TAC connection consists of a single wire (can't make out the exact color) that goes to the negative side of the coil. I assume I have to disconnected it from the negative of the coil (as per MSD's instruction), remove the inline filter and then use the TAC connection on the side of the MSD unit. (?)
Can you expand on that some? Are you speaking of the internal wires in the tach? Since I am replacing the fuel gauge, and had no tach, I have no 'stock' tach wires. I have to run a trigger wire on my own + ignition + ground from the back of the OEM tach I just installed.Brown wire to coil and Brown to circuit board connector for '68. It is a straight wire to/from fuse block. Power is Pink wire in connector.
I will give this a try. I do have the 8920, which did not work. The tach would not work at all the way I wired it. I admittedly am being a little lazy on this because I have my engine compartment exactly the way I want it (some Team Camaro members have seen it at Hot August Nights) and don't want to remove the box.I had the same problem when I pulled my fuel gauge and put in a oem tach. Since I had a MSD distrubutor I called their tech line and talked to one of there techs. They were super nice and they sent me 3 tach filters because he said they were not sire which would work. It had instructions and i didnt pay for it. They even paid for shipping. My tach is now good.