Author Topic: How are you routing your engine wiring harness?  (Read 945 times)

Offline Stewart G Griffin

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How are you routing your engine wiring harness?
« on: September 13, 2021, 09:31:54 PM »
Generally, a lot of engine wiring harnesses go to the alternator, then to the starter.

Let's say MOST SBC engine wiring harnesses are laid out this way.

How are you routing yours?  (i know, i did not take a picture.......)   

After plugging into the alternator, i think behind the alternator.   But then what after that?   Below the engine perches or above?   The diagrams i'm seeing aren't real clear, but it looks like it should probably run along the oil pan?


Is there a diagram that shows the layout/routing?

Offline 1980K20

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Re: How are you routing your engine wiring harness?
« Reply #1 on: September 13, 2021, 09:45:10 PM »
My new wire harness instructions had the alternator wire routing to starter, not the battery. My EFI instructions say to connect directly to the battery to get a capacitive frequency filter effect from the battery. There's something that looks like a filter or maybe a fusible link in the wire from the alternator, so I followed the directions.

I routed the battery cable and the alternator cable and the solenoid wire along the engine block and am using one of those loop insulated cable clamps on the frame rail to hold it in place. I didn't see any place on the block to add a retention device.

No pictures yet. Will post pictures on a thread that I started asking for people's pictures when I'm done.

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1952 International L112 - waiting for EV conversion
1967 Camaro - 250 six cyl, 200-4R
1980 K20 4x4 Fleetside - 350 SBC roller Cam, TH350

Offline Chevymanbill

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Re: How are you routing your engine wiring harness?
« Reply #2 on: September 14, 2021, 08:02:18 PM »
Your Alt. harness is part of the starter harness. It does not go under the engine towers. It comes from the back right side of the engine and runs along the inside of the passenger side Valve cover. There should be a short metal tube behind the right head that the starter harness fits through. It bolts to one of the trans. to block bolts. If you have A/C, you should have wires for the Evap. box before it reaches the alt.

Offline 1980K20

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Re: How are you routing your engine wiring harness?
« Reply #3 on: September 14, 2021, 08:46:43 PM »
Does that mean the battery cable also routes along the fenders (inside the fender for me), the firewall and then down to the retention on the back of the head? I've found that bolt position on the head. I can see how that gets it out of the way.

Picture? Pretty please?

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1952 International L112 - waiting for EV conversion
1967 Camaro - 250 six cyl, 200-4R
1980 K20 4x4 Fleetside - 350 SBC roller Cam, TH350

Offline 75gmck25

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Re: How are you routing your engine wiring harness?
« Reply #4 on: September 25, 2021, 05:39:59 PM »
The original routing for the positive battery cable on my '75 is:
- positive battery terminal down to a wire retainer that is bolted to the top of the frame rail near the fuel pump
- then running down next to the fuel pump and parallel with the bolts on the side of the oil pan.  There should be at least two wire retainers on the pan bolts.
- at the rear of the pan it connects to the large terminal on the starter.

Also connected to the large terminal on the starter:
-  alternator charge wire with fusible link runs up the back of the engine through a protective metal tube and up  to the top of the valve cover, then down the top of the valve cover to the BAT terminal on the alternator.  On the top of a stock valve cover there are retainers for the wire, which runs through the plastic flexible tubing.
- power to cab has a wire with fusible link that runs up the back of the engine through the metal tube, then across the back of the firewall to the junction that is next to the brake booster.  This is your always-on 12 volt power to the entire truck.  That power wire is usually the one that goes straight down from the wire junction.

If you really want to see a picture, I can try to reduce mine to a size that can be posted.  Originals from my camera and phone are too big.

Offline 1980K20

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Re: How are you routing your engine wiring harness?
« Reply #5 on: September 26, 2021, 10:32:03 AM »
Hi Gmc75k25,

Thanks much for the description!

I'd appreciated a picture of you can! On my android phone, when I open the picture, there's a little icon, looks like a crayon, on the norm. I click to edit. Upper right there's an option to resize. I choose 40%, seems to come out well. Save and you're done. I usually make a noticeable change, zoom in and crop so I can tell what's big and small when looking at the gallery.

Mark

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1952 International L112 - waiting for EV conversion
1967 Camaro - 250 six cyl, 200-4R
1980 K20 4x4 Fleetside - 350 SBC roller Cam, TH350

Offline JohnnyPopper

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Re: How are you routing your engine wiring harness?
« Reply #6 on: September 26, 2021, 03:50:05 PM »
Search this site for PIXresizer. It's an app that works really well.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline 1980K20

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Re: How are you routing your engine wiring harness?
« Reply #7 on: December 12, 2021, 12:47:32 PM »
Here's my wiring harness routing. Thanks for the help and suggestions! I made some changes along the way due to your help.

Mark

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1952 International L112 - waiting for EV conversion
1967 Camaro - 250 six cyl, 200-4R
1980 K20 4x4 Fleetside - 350 SBC roller Cam, TH350

Offline 1980K20

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Re: How are you routing your engine wiring harness?
« Reply #8 on: December 12, 2021, 01:57:41 PM »
Realized I hadn't finished cleaning up the wires by the lights. Here are both sides. You can see the ground harness, bolt with lots of ground wires to it. One on each side, also one in the back for the taillights, each with a solid ground. I do not rely on chassis ground anywhere in the truck.

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1952 International L112 - waiting for EV conversion
1967 Camaro - 250 six cyl, 200-4R
1980 K20 4x4 Fleetside - 350 SBC roller Cam, TH350