71 factory tach calibration

[tak419]

My 71 B-body tach works fine but reads high. The tach is reading about 800rpm high, is there a way to calibrate/adjust these ?

 

[mrsnicks]

I'm on the fence about this. https://www.ebay.com/itm/Mopar-Repl...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649 Anyone have any real world experience with them?

 

[tak419]

I'm on the fence about this. https://www.ebay.com/itm/Mopar-Replacement-Tachometer-board-RT-ENG/161119693854?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649 Anyone have any real world experience with them?

That didn't really answer my question of is thee a way to calibrate or adjust the Factory tach, not looking to replace my board. As for RT's products they make really nice quality stuff.

 

[Goldmember72]

I had the same problem with my 72 Charger and had asked the same question but was told there isn't any adjustment. I did order and install the instrument voltage regulator and new tach board from RTE. This is the original tach board and from what I can tell the pot adjustment is the item I placed a black box around. I did not attempt to calibrate it while still installed, but it did cross my mind. This is very close to where it was on adjustment but I did try moving it with a screwdriver and it does move so I would think it is adjustable. The problem I had was the amount mine was off at idle was about 400 and as you increase engine speed it would be off by about 1000 by indication of 3500 (actual 2400). It took awhile to remove/install the whole panel and I was concerned I wouldn't be very close across the whole RPM range. If you do decide to do the factory board adjustment, please let me know how it worked out. The new board from RTE didn't need adjustment at idle but I did have to make a slight adjustment at 4000. The tach is very accurate and stable now with the new board. Good luck.

 

[Billccm]

To adjust properly you have two points. One is near mid rpm which would be the potentiometer and the other is the movement spring near 900.
I second the rt-eng.com tach board with built-in calibrator. Very nice, bench calibration and accurate.

 

[tak419]

To adjust properly you have two points. One is near mid rpm which would be the potentiometer and the other is the movement spring near 900.
I second the rt-eng.com tach board with built-in calibrator. Very nice, bench calibration and accurate.

I took mine out and seen the adjustment pot on the back. I'm assuming the movement spring adjustment is going to be made by the large ( straight slotted) screw that is on the front side on one end of the spring ?

 

[Billccm]

I took mine out and seen the adjustment pot on the back. I'm assuming the movement spring adjustment is going to be made by the large ( straight slotted) screw that is on the front side on one end of the spring ?

The screw is the jewel setting. The spring is adjusted by oh so slightly rotation of the phonelic connector pad.

 

[tak419]

Thanks