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Old 06-10-2019, 02:22 PM   #1
jpgl
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wiring harness

is the underhood wiring harness in a 1970 chev the same as a 1971 chev both trucks had full gauges ?is there a difference between a big block and small block harness?
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Old 06-10-2019, 04:16 PM   #2
Steeveedee
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Re: wiring harness

I expect the wiring harnesses should be similar. Look around at different engines. Some year they switched sides with the alternator. '70 and '71 should be pretty close, but depending on end user, there may be emission controls on one but not the other. If you can, put the vehicles next to each other and do a "what is wrong with this picture?" exercise.
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Old 06-10-2019, 06:55 PM   #3
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Re: wiring harness

There are two underhood harnesses. One goes to the engine and the other crosses the radiator.
I'd go to wiringharness.com and check the part numbers, engine applications, and years.
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Old 06-11-2019, 04:54 AM   #4
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Re: wiring harness

The wiring harnesses for the engine are the same both years. Big block is different, the starter wires are much longer as they are routed along the intake to the front of the engine then down by the oil pan to the starter. The temp wire is a little shorter on a big block and has a metal retainer for the back of the head. You can make it work, same wires just different routing.
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Old 06-11-2019, 10:21 AM   #5
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Re: wiring harness

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Originally Posted by randy500 View Post
The wiring harnesses for the engine are the same both years. Big block is different, the starter wires are much longer as they are routed along the intake to the front of the engine then down by the oil pan to the starter. The temp wire is a little shorter on a big block and has a metal retainer for the back of the head. You can make it work, same wires just different routing.
What year(s) do the starter wires do that? Mine run along the trough on the firewall and route down the back of the block. It's a factory 402.
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Old 06-11-2019, 11:20 AM   #6
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Re: wiring harness

I think all years of big block are routed that way.
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Old 06-11-2019, 05:07 PM   #7
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Re: wiring harness

I've never seen that. Looking at pages 323 and 395 of the Factory Assembly Instruction Manual, it shows the wiring running along the cowl and along the back of the block to the starter.
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Old 06-11-2019, 05:30 PM   #8
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Re: wiring harness

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Originally Posted by Steeveedee View Post
I've never seen that. Looking at pages 323 and 395 of the Factory Assembly Instruction Manual, it shows the wiring running along the cowl and along the back of the block to the starter.
I see that, maybe true on early trucks, those are really just parts trucks for the 71-2 years, and hose for sure its routed around he front. See pics here. Look for s set of wires by the passenger valve cover st the front.
Assembly manual also shows temp sensor at thermostat too and over speed switch by carburetor(c60 stuff)
http://67-72chevytrucks.com/vboard/s...d.php?t=442467
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Old 06-12-2019, 09:50 AM   #9
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Re: wiring harness

OK, then. Never seen it is all. I wonder why they were routed two different ways?
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Old 06-12-2019, 11:27 AM   #10
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Re: wiring harness

Id like to be able to get an engine harness that doesn't have the emission controls wiring. Do they sell a replacement one that plugs in and has just the needed wires and not the emission wires?
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Old 06-12-2019, 01:54 PM   #11
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Re: wiring harness

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Originally Posted by demian5 View Post
Id like to be able to get an engine harness that doesn't have the emission controls wiring. Do they sell a replacement one that plugs in and has just the needed wires and not the emission wires?
Just open the old harness and remove what you don't want then retape .

https://www.inlinetube.com/products/inl10377

original taping method

https://www.youtube.com/watch?v=MehjltOq-jc

lectriclimited harnesses

https://www.lectriclimited.com/vehic...ke/21/model/56
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Old 06-12-2019, 03:04 PM   #12
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Re: wiring harness

The emissiins is only tcs, transmission controlled spark and its a seperate harness.
There are only a few engine harness wires and all are needed.
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