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TBI to carb swap - Now, tach and speedo no workie

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Old 07-26-2001, 09:11 AM
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TBI to carb swap - Now, tach and speedo no workie

I just swapped from TBI to a Holley 750 carb and my tach/speedo don't work. I'm fairly sure if I hook up the white wire (that currently splits at a grey connector) to the coil I'll get tach, but where's the signal from the speedo come from? Is it tach related and I'll get that back as well after hooking up the tach? Or is it tranny related and I should look there? Any help is appreciated,


Steve

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Old 07-26-2001, 07:31 PM
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Car: 1990 Pontiac Trans Am
Engine: 355 TPI siamesed runners
Transmission: Tremec T56
Axle/Gears: 12-Bolt 3.73
If I remember correctly, the input from the speedo in the trans goes to a speedo buffer, then from there its to the computer and the speedometer. But, it might go from the speedo buffer to the computer and then to the speedometer, in which case it wont work since you've eliminated the computer. Check your Helm's manual for the diagram...

The tach I dont know, sorry...

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Old 07-27-2001, 08:18 PM
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Car: 1989 Firebird Formula
Engine: Internal Combustion
Transmission: Completed
Axle/Gears: ones that turn.
Steve, check in the 'tech' link in my sig; I have an article on installing an electric speedo and what you'll need to hook yours back up.
Your theory on the tach sounds good...it should work that way.

Pete

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Old 07-28-2001, 09:09 AM
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I'll check it out and get back to ya...


Thanks,
Steve

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