L29 swap

[Dave69]

First post here , not sure it’s in the right place but,,. I have a 1995 k3500 drw 6.5 diesel. I have a low k 97 7.4 vortec I’m swapping into the truck. I also have a 1997 k 2500 5.7 truck for bits and pieces. I have the 7.4 engine wiring harness , unfortunately it’s from a van so I assume it’s different than the truck one? The 5.7 vortec engine harness is also different (spider injector) . Any ideas on the best move would be appreciated. Once I get the harness fitted up for the 7.4 I will be swapping the ecm to the 0411 also.

 

[L31MaxExpress]

First post here , not sure it’s in the right place but,,. I have a 1995 k3500 drw 6.5 diesel. I have a low k 97 7.4 vortec I’m swapping into the truck. I also have a 1997 k 2500 5.7 truck for bits and pieces. I have the 7.4 engine wiring harness , unfortunately it’s from a van so I assume it’s different than the truck one? The 5.7 vortec engine harness is also different (spider injector) . Any ideas on the best move would be appreciated. Once I get the harness fitted up for the 7.4 I will be swapping the ecm to the 0411 also.

On my 8.1L Tahoe, I married the van engine harness to the Tahoe fuse box, C100 connector and body harness. Once you get the diagrams in hand, there are very few connections to remove to separate the two harness sections. The van harness was a little long between say the thermostat housing and PCM, but that allowed me some more freedom on routing.

 

[L31MaxExpress]

Wiring is not overly difficult for me though. I am about to marry that unused van body harness side I have to a 2015 6.0L van harness and re-pin it from an E78 to an E67 GenIV LS PCM. Thats going to be a fun one given the sheer amount of wiring there and changes to be made. Plenty to delete and change in it like the VVT and 8-pin MAF wiring and the added body side wiring. I probably have 15-20 GM harnesses boxed up at the shop from everything from a CPI S10 to a 6.5L diesel to a L31 Suburban to a DBW GMT800 LS. I save them to have runs of color matching wire and replacement connectors as needed.

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[Dave69]

Sounds like too much wiring for me ! I’m gonna take a closer look at the harnesses and see what I got. I did read somewhere about changing the injector plug on the 5.7 harness to fit the 7.4 plug.

 

[vr1967]

Also the 7.4 Vortec I had, had 2 knock sensors instead of 1 like I’ve seen on most 5.7s but that is simple enough to add

 

[L31MaxExpress]

Sounds like too much wiring for me ! I’m gonna take a closer look at the harnesses and see what I got. I did read somewhere about changing the injector plug on the 5.7 harness to fit the 7.4 plug.

That is a fairly easy thing to do, also likely need to extend some wiring for the TPS and IAC. I converted my L31 harness to run my marine intake using an AEM injector subharness and matching Detschewerks connector.

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Here are the injector wire colors for the PCM ground. All the power wires are Pink. These were my notes on converting the stock harness to AEM and from the stock MAP to the Bosch T-Bar marine map.

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[Dave69]

That’s good info, looks simple enough. I will take a look at the harness later today. Thanks for the pics and info.

 

[Scottm]

Did you do the swap? Also the knock sensor wires are combined before the ecm, so it won't know which side actually knocked.

 

[L31MaxExpress]

Did you do the swap? Also the knock sensor wires are combined before the ecm, so it won't know which side actually knocked.

GM PCMs used on sequentially injected stuff knows what cylinder knocked. The PCM knows which cylinder is firing when the knock sensor is rattled. There is a knock sensitivity adjustment by cylinder.

 

[obsk yesing97]

7.4 going to 8.1 wiring help?