It is ridiculous to say the tach calibration pot should be fully left, mid-range, and/or fully right for the particular engine whatever it may be. There are too many variables caused by corrosion, sensor deterioration, voltage drops, etc. etc.. The only way to get it right is to set the dash tach pot to the same RPMs as recorded to a known correct standard, like a handheld tach. This applies to all gauges, they have to be compared to a calibrated standard gauge to be spot on. Otherwise you're just pi$$ing in the wind. :cheers: