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Tach/Dwell reading question.

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Old 01-14-2009, 08:47 PM   #1
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Car: 85 Firebird & Grand Prix GXP
Engine: LG4 305 (originally 2.8L V6)
Transmission: 700R4
Axle/Gears: 10 bolt 3:43 Open Diff.

Tach/Dwell reading question.

Anyone know how I use / where I hook up a tach/dwell meter on the GM remote mount coil I have in the car or if I can even use it on this car?
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Old 01-15-2009, 12:25 AM   #2
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Car: 82 Berlinetta/57 Bel Air
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Axle/Gears: 12B-3.73/9"-3.89


Do you have a points/condenser distributor?
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Old 01-15-2009, 05:58 AM   #3
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Re: Tach/Dwell reading question.

Dwell is non-adjustable on an electronic distributor.

If you wanted to check dwell anyway, you attach it to the same place the tach signal wire is hooked up and attach the other lead to a good ground source. On a divorced coil HEI that would be the smaller white wire going to the coil- the plug that goes to the vehicle's wiring harness, not the one that goes to the distributor.
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Old 01-15-2009, 06:19 PM   #4
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Car: 85 Firebird & Grand Prix GXP
Engine: LG4 305 (originally 2.8L V6)
Transmission: 700R4
Axle/Gears: 10 bolt 3:43 Open Diff.

Re: Tach/Dwell reading question.

Pretty sure it's not a points distributor. I know that I don't need to check dwell, I was more interested in the tach feature. I don't have a tach on my car at all and want to know where it's idleing. I can't figure out the wire though. The directions for the meter show where to hook up on a bunch of different coil types but not the remote coil I have.



My coil looks like the one below but OEM stock.
Click the image to open in full size.
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Old 01-16-2009, 01:04 AM   #5
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Tap into the white wire coming off the coil.

Wait, you have an '85? You need to connect the red lead for the dwell/tach to the wire that is not the power to the coil, the other dwell/tach lead to ground.
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Old 01-16-2009, 07:28 AM   #6
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Re: Tach/Dwell reading question.

Yeah, if it's an 85 the coil is mounted on top of the distributor under a dust cover. It's what they used before they went to the divorced coil HEI distributors around 1988.

I didn't catch that the first time through.

You should see the word "TACH" molded into the coil cover on top of the distributor, on the square part that sticks out the driver's side. Plugs go on from underneath that area. You'll see the big pink power wire right next to the TACH terminal. That TACH terminal is where you would hook up a tach signal wire or one of your dwell meter leads.
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Old 01-16-2009, 08:07 AM   #7
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He said he's got an external coil. Must have been swapped in.
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Old 01-16-2009, 05:37 PM   #8
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Car: 85 Firebird & Grand Prix GXP
Engine: LG4 305 (originally 2.8L V6)
Transmission: 700R4
Axle/Gears: 10 bolt 3:43 Open Diff.

Re: Tach/Dwell reading question.

Yes, its a divorced setup and the motor is an '87 or later. How am I tapping in to the wire? Its has two plug type connections that connect in the female end of the coil I pictured above.
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Old 01-16-2009, 06:50 PM   #9
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Re: Tach/Dwell reading question.

If your car already has a tach (like 3rd gen Camaors and Firebirds do) then you'll have to piggy-back a connection onto the stock tach wire. Read my first post above for info on which wire that is.

If the vehicle does NOT have a factory tach the connection point is still there on the plug, but there's usually just a short pigtail of wire taped up on the connector, not attached to anything. That's the wire. Common in truck applications that don't have a factory tach.
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Old 01-16-2009, 08:47 PM   #10
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Car: 85 Firebird & Grand Prix GXP
Engine: LG4 305 (originally 2.8L V6)
Transmission: 700R4
Axle/Gears: 10 bolt 3:43 Open Diff.

Re: Tach/Dwell reading question.

No, I don't have a tach and I don't have a pigtail wire.
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