tach reading
Burning Brakes
Joined: Nov 2006
Posts: 954
Likes: 40
2022 C3 of the Year Finalist - Modified
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
These electronic tachs are not all that accurate based upon my observations. I've repaired a few tach boards for forum members and always try and calibrate them the best I can when they are fixed. The ones I've done have been off as much as 4-500 RPM in the midrange, right about where you are measuring at. The middle seems to be the worse spot as far as accuracy goes.
The most recent one I did was reading about 3400 at a 3000 rpm input. You can trim them a little bit but the circuit itself does not lend itself to accurate linear operation and can only be adjusted at one end or the other. I've found no way to get the original circuit accurate across the complete rpm range.
If you want to be sure, just beg, borrow or ste....... ah acquire a dwell/tach, timing light w/a tach or similar that get's it's signal from the #1 plug vs using the distributor tach output and compare what it reads to the stock tach. I am willing to bet that most C3 electronic tachs will be off by a fair amount at some point on the dial.
FWIW. Good Luck!
The most recent one I did was reading about 3400 at a 3000 rpm input. You can trim them a little bit but the circuit itself does not lend itself to accurate linear operation and can only be adjusted at one end or the other. I've found no way to get the original circuit accurate across the complete rpm range.
If you want to be sure, just beg, borrow or ste....... ah acquire a dwell/tach, timing light w/a tach or similar that get's it's signal from the #1 plug vs using the distributor tach output and compare what it reads to the stock tach. I am willing to bet that most C3 electronic tachs will be off by a fair amount at some point on the dial.
FWIW. Good Luck!
