Took my '63 Biscayne out of storage today and after changing oil, grease, check tires, etc. I had my friend help me cut the dash panel and install my '63 SS factory tach. A bit more work than we thought, but done nicely. However, driving it home I notice it read a full 1K RPMs high... Strange ???? I am sure we have it hooked up correctly. So question. Do I need a "Filter of some kind" (I saw that once) due to not having the old points distributor ? Also the one I have is for a 409 and I am running a beefed up 283 with HEI ignition.. Any help would be appreciated. Thanks much...
I have used the same tach with a point distributor and then with a HEI unit. There was no change in the RPM readings. I simply hooked up the coil pick up wire from the tach to the terminal marked "tach" on the HEI unit. Nice car, by the way, Bob
Have something similar on mine, when it starts the tach kinda goes crazy (hei setup) but after it warms up tach settles down and reads right. I've thought some RF interference might be causing it. One side note, i have a killer timing light that works on anything -except MSD component ignitions. If you have msd, that might be the problem with the older tach components.
Not an answer I remember replacing my 6000 rpm tach in my 64 with a stewart warner tach and created a high RPM misfire I traded the Stewart Warner for a 7000 rpm 409 tach and every thing was fine. Bur that was with points.
As always, appreciate the prompt answers.. As as result I have been looking at tach filters.. Interesting, but some say only for their brand gages... will not guarantee to work on others.. I assume this is normal BS to push their products.. Also willing to try one, but from all the reading I have done this refers to bouncing or erratic needles.. My needle is totally stable, but just not accurate.. when going 60 mph I normally run ~3000 rpm..(Checked this on a chart using my rear end, trans gearing numbers and tire size several times) but this one reads ~4000 at that speed. Also when getting on it a bit I usually shift at ~5200 rpm, and this one will peg at 7000 rpm. Don't want to spend the $$$ and work to put in a filter if it is not going to get it accurate. If nothing else I will leave it, as I know where it reads high.. Lastly, I only drove it about (20) miles home.
Sounds to me like the tach needs a "calibration" or resetting in the guts (was an inst.tech for work). Depending upon the circuit, some of them have a "pot" in them that can be adjusted for span. The zero looked a little off so it should be able to be re-zeroed a little closer. Incidentally, the zero is not necessarily linear, it might be a multiple type. A good electronic tech could prob. help you.
Thanks, Will do some checking around. Also it was running when I took this picture, hence the zero off...
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