Tachometer is inaccurate

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cudaboy1965

cudaboy1965

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Any wisdom on why my stock in-dash tachometer is inaccurate and reading high?
1967 formula S / 383 with MSD 6A and an MSD tach adapter.

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What distributor is used for trigger? The adapter gets around multi-strike, but noise issues from ignition can generate false triggers. That can happen if wiring layout couples plug wires, with ignition trigger.
 
I know that when you send an original tach into a shop to get it calibrated, they usually redo the innards so it will handle both the original ignition system AND the newer electronic ignitions. In other words, the factory tach is not guaranteed to properly read your upgraded ignition.

The following is from a description for a new tachometer.
"Will work with many different types of ignition systems including breaker point, electronic ignition, even MSD or Pertronix ignition systems."
 
Last edited:
KitCarlson said:
What distributor is used for trigger? The adapter gets around multi-strike, but noise issues from ignition can generate false triggers. That can happen if wiring layout couples plug wires, with ignition trigger.
Click to expand...
Stock distributor
 
g413 said:
I know that when you send an original tach into a shop to get it calibrated, they usually redo the innards so it will handle both the original ignition system AND the newer electronic ignitions. In other words, the factory tach is not guaranteed to properly read your upgraded ignition.

The following is from a description for a new tachometer.
"Will work with many different types of ignition systems including breaker point, electronic ignition, even MSD or Pertronix ignition systems."
Click to expand...
Thanks
 
Is it possible the adapter is just to close to the distributor and picking up noise?

Of course it is possible. :D
 
The stock distributor has points, if that is what you are using the points are bouncing.

Try a premium set of points, and correctly adjust.

If you have access to an automotive scope use that to view coil primary.
 
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TrailBeast said:
Is it possible the adapter is just to close to the distributor and picking up noise?

Of course it is possible. :D
Click to expand...
The tach reading is very smooth. Just incorrect.
I am reading on-line instructions for MSD tach adapter. Don't know if my car was originally voltage or current triggered.
 
The tach reading is very smooth. Just incorrect.
I am reading on-line instructions for MSD tach adapter. Don't know if my car was originally voltage or current triggered.
 
my oem tachometer is around 400 rpm to fast... no matter if I use a stock distributor...oder a MSD RTR .. distributor... looks like a factory "mistake "...

I can live with it...also because I have automatic transmission

Greetings Juergen
 
RTR. What is it. Who makes it?
Yjink I will clone a newer tach into my bezel
brasil said:
my oem tachometer is around 400 rpm to fast... no matter if I use a stock distributor...oder a MSD RTR .. distributor... looks like a factory "mistake "...

I can live with it...also because I have automatic transmission

Greetings Juergen
Click to expand...
TRr
 
The innards originally were electric. New electronic boards can be had for $80. Im interested in your tach if ya wanna sell it.
 
cudaboy1965 said:
I'll dive into this over the winter
Click to expand...
Last winter I carefully calibrated my 67 tach together with my ECU and the MSD tach adapter. The old tach was set to show correct revs...But, now with everything in the car, the tach suddenly reads significantly higher rpms...reason so far unknown...
 
SwedeCharger67 said:
Last winter I carefully calibrated my 67 tach together with my ECU and the MSD tach adapter. The old tach was set to show correct revs...But, now with everything in the car, the tach suddenly reads significantly higher rpms...reason so far unknown...
Click to expand...
Thanks
 
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