Hello, bought a repro rallye tach from Year One for my 70 Challenger. I'm not happy how it works.
The pointer on idle flexes back and forward about 300RPM. Above 4000RPM it flexes more than 1500-2000RPM.
Have a Petronix ignition in the car.
Tried new wiring without help.
Need input if somebody have had the same problems or if the tach is working correct when mounted in your car.
Year One send a replacement, but don't want to mount it back.
Peter

I'll "assume" the tach being repro, has upgraded internals, the Pertronix ignition upgrade sometimes interferes with original tachs as well,...you'll need a "tach filter"

Dayclona thanks for your answer.
The tach i bought is a reproduction, made in US.
My org tach worked for 6 years (with petronix ignition)

Who makes a tach filter? MSD
peter

I agree that a filter would help. You may consider the tach Redline gauge works sells w/ the VDO internals. Had one in my hemi challenger & no need for a tach adapter & it was really accurate.