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#1 |
425hp409
![]() Join Date: Oct 2008
Location: Prosper Texas
Posts: 841
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Re: Tachometer calibration
I found a previous thread that addresses calibrating it with an adjusting screw that is at the top rear of the tach that is covered by tape.
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Charles 68 SWB, Dad bought new, now 396 & factory ac 64 Impala SS, 409 425HP, 4 speed AC 64 Bel Air Wagon, 400 Small Block 57 Bel Air all original 283 w/Factory Air 77 GMC Sprint, 454/425HP 67 Olds 442, all original 90 ZR1 Corvette |
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#2 |
Registered User
Join Date: Feb 2011
Location: Modesto, CA
Posts: 2,189
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Re: Tachometer calibration
I can add that, I have a tach that was reading low, also HEI. I assumed the board was bad and replaced it, using a new board from Cajun Tach shop. It still reads exactly the same, and has a hangup where it will freeze.
I assume the issue is with the physical mechanism needing recalibration, not the electronics. |
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#3 |
425hp409
![]() Join Date: Oct 2008
Location: Prosper Texas
Posts: 841
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Re: Tachometer calibration
I hooked up 3 tachs to a car with a digital timing light for a reference tach and 2 calibrated perfectly throughout the rpm range with the screw in the back. The 3rd would calibrate at idle, but read 2000 when it should have been 2500. I have 2 more to check tomorrow. ps: The test car had HEI and one of the tachs had previously been in my truck with point ignition. It read the same before calibration with both ignition sources. The tack reads ignition pulses, and doesn't care if it is HEI or Points.
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Charles 68 SWB, Dad bought new, now 396 & factory ac 64 Impala SS, 409 425HP, 4 speed AC 64 Bel Air Wagon, 400 Small Block 57 Bel Air all original 283 w/Factory Air 77 GMC Sprint, 454/425HP 67 Olds 442, all original 90 ZR1 Corvette Last edited by 425HP409; 07-26-2023 at 10:30 AM. |
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#4 | |
70+ ( Old Skool Club )
![]() Join Date: Nov 2003
Location: Saskatoon, Saskatchewan ,Canada
Posts: 9,163
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Re: Tachometer calibration
Quote:
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