HEI power and Tach wire - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 14 (permalink) Old Sep 14th, 19, 6:31 PM Thread Starter
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HEI power and Tach wire

I have a power wire ran from the fuse box to the HEI and I’m trying to install a tach. Can I connect into this same wire or where do you recommend wiring it?
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post #2 of 14 (permalink) Old Sep 14th, 19, 6:34 PM
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Re: HEI power and Tach wire

HEI distributor has a tach connection next to the power wire. The cap should be marked 'tach'.

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post #3 of 14 (permalink) Old Sep 14th, 19, 10:01 PM Thread Starter
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Re: HEI power and Tach wire

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Originally Posted by pnugene View Post
HEI distributor has a tach connection next to the power wire. The cap should be marked 'tach'.
Yes which is Green. I also have a Red (power). Black (ground) and white (light on the tech). I'm trying to figure out where to run the red power wire.

1970 Chevelle
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post #4 of 14 (permalink) Old Sep 14th, 19, 10:26 PM
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Re: HEI power and Tach wire

Pictures??

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post #5 of 14 (permalink) Old Sep 14th, 19, 10:28 PM
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Re: HEI power and Tach wire

Red goes to ignition I.e. fuse box....

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post #6 of 14 (permalink) Old Sep 14th, 19, 11:49 PM Thread Starter
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Re: HEI power and Tach wire

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Originally Posted by jrkrace View Post
Red goes to ignition I.e. fuse box....

Yes I understand that but I already have a 10 gauge wire connected there that powers the HEI. I'm trying to figure out if I can splice into that wire and power the tach or if I need to wire it somewhere else

1970 Chevelle
327/TH350, Bear 13" front, 12" rears, UMI upper/lower A arms, UMI front 1.25 sway bar, UMI rear upper/lower control arms, Ridetech drop spindle, Viking coilovers front/rear, 12 bolt, work in progress
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post #7 of 14 (permalink) Old Sep 14th, 19, 11:58 PM Thread Starter
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Re: HEI power and Tach wire

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Originally Posted by LeoP View Post
Pictures??
Bellow is the tach I ordered from amazon and I attached a diagram for the wiring. Being I already have a wire running to the switched 12V for the HEI, I want to know if I can splice into that but I'm afraid of taking voltage away from the distributor



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1970 Chevelle
327/TH350, Bear 13" front, 12" rears, UMI upper/lower A arms, UMI front 1.25 sway bar, UMI rear upper/lower control arms, Ridetech drop spindle, Viking coilovers front/rear, 12 bolt, work in progress
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post #8 of 14 (permalink) Old Sep 15th, 19, 9:12 AM
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Re: HEI power and Tach wire

Yes, you can splice into the hei power wire.

Your just jealous because you can't hear the voices!

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1963 Plymouth Fury 440/Torqueflite
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post #9 of 14 (permalink) Old Sep 15th, 19, 12:40 PM
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Re: HEI power and Tach wire

That is correct, both HEI power, and tach power will work just fine piggybacked together on the IGN fuse box terminal. I'd run the tach ground to the engine, and TACH on the cap is the tach signal feed.
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post #10 of 14 (permalink) Old Yesterday, 12:04 PM Thread Starter
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Re: HEI power and Tach wire

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Originally Posted by Dave Ray View Post
That is correct, both HEI power, and tach power will work just fine piggybacked together on the IGN fuse box terminal. I'd run the tach ground to the engine, and TACH on the cap is the tach signal feed.
As for the ground your saying to ground it to the engine block?

1970 Chevelle
327/TH350, Bear 13" front, 12" rears, UMI upper/lower A arms, UMI front 1.25 sway bar, UMI rear upper/lower control arms, Ridetech drop spindle, Viking coilovers front/rear, 12 bolt, work in progress
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post #11 of 14 (permalink) Old Yesterday, 2:23 PM
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Re: HEI power and Tach wire

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Originally Posted by Tony70Chevelle View Post
As for the ground your saying to ground it to the engine block?
Any convenient chassis ground will work.

Your just jealous because you can't hear the voices!

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post #12 of 14 (permalink) Old Yesterday, 3:30 PM
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Re: HEI power and Tach wire

Run the red wire to a switched terminal at the fuse box. The HEI power wire, if its fused at all, would be fused for to high of a load to protect the car from fire if the tack decides to short out...
I would fuse the tach @ 5 amps..
Also do you want the car shutting down if the tach decides to go south on you and blow the circuit.. That HEI has a dedicated circuit for many reasons. I'd leave it alone..
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post #13 of 14 (permalink) Old Yesterday, 4:46 PM
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Re: HEI power and Tach wire

The engine is the best ground distribution block you will ever find. Chassis/body is not the first place the ground cable from the battery goes, it is the engine.

Fusing an HEI is not needed. First start up amperes can run well past 5 amperes, so, 5 amp fuse is too low, if fusing is done.
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post #14 of 14 (permalink) Old Yesterday, 4:54 PM
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Re: HEI power and Tach wire

Quote:
Originally Posted by hydro462 View Post
Run the red wire to a switched terminal at the fuse box. The HEI power wire, if its fused at all, would be fused for to high of a load to protect the car from fire if the tack decides to short out...
I would fuse the tach @ 5 amps..
Also do you want the car shutting down if the tach decides to go south on you and blow the circuit.. That HEI has a dedicated circuit for many reasons. I'd leave it alone..
The HEI in this case does not have a dedicated circuit because the car did not come with one stock. The OP is using the IGN term. in the fuse box which is fused through the adjacent fuse. The tach does not require a fuse as an internal short is usually contained inside the tach. And yes standard failure indication of a bad tach is the car will shutdown and/or refuse to start because it grounds the coil- terminal.

Your just jealous because you can't hear the voices!

1967 Olds Cutlass 468 BBC/T400
1963 Plymouth Fury 440/Torqueflite
2007 Ford Mustang GT (momma's car)
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