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LS Motor into your K5

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  • LS Motor into your K5

    Alright im gunna get this started. this will take me a while so bear with me! Im still not sure how im going to organize the info so i will be changing it up a bit as i go along. ill be adding pictures and links later. this is a rough draft to get my ideas down!


    I am not a professional, I do not do this all the time, this is the only swap i have done. There a a ton of ways to skin this cat. your results and budgets will vary

    lets get started!!

    to start, ill post what i started with and what i used

    I have a 1990 K5 blazer that came with a 5.7 350TBI, 700r4, and NP241c.


    your options for donor motors are almost limitless. I used a 5.3L LM7 from a 2004 Tahoe that i bought from Bryan at BD Turnkey Engines . i also opted for the upgraded LS6 cam and LS6 valve springs. It came with a Drive By Wire (DBW) throttle body and also had no EGR and it also has a returnless fuel system. The transmission i Used was originally from a 2004 tahoe as well (didnt plan on that, just dumb luck) and was custom built by Westminister Performance Transmission.


    To bolt the 5.3 in place i used the DIrty Dingo adustable motor mounts. I used these because you still use the factory style clamshell motor mounts for the 350. I replaced them with some Poly ones. i pushed the motor all the way back in the mounts. i did have to remove the factory AC compressor and bracket to fit. also, the front drivers side corner of the oil pan was about 1/8" above the factory engine cross member, so i beat the crossmember with a hammer till i got about 1" of clearance. the factory exhaust manifolds fit really tights, but i only had to trim about a 1"x3" notch out of the upper frame rail on the drivers side to make it fit. The 4l60e bolted right to the back of the 5.3 and bolted directly to the factory transmission crossmember. no adapters needed! Win! also the NP241c bolted directly to the back of the 4L60e! Double Win! so now the drivetrain is in nice and tight. the tripple win came in when i realized i could use my factory driveshafts.


    so, the 5.3 has the returnless style fuel rail. the 350 was a return style. Parts i used was a Walbro 255, and a corvette filter/regulator and some braided stainless line and adapters.

    First, i cut both factory fuel lines from te motor all the way back to the part of the frame rail right before it goes up. there were 2 lines. they were a combo of hard and rubber lines. I then placed the corvettet regulator/filter on the frame rail and hooked the exsisting fuel out line (the line coming from the tank) and hooked it in to the regulator. the the return line (The one that would carry fuel back to the tank) to the regulator. then i used the braided fuel line to run the the fue out side of the regulator to the fuel rail on the motor. In the tank i replaced the factory fuel pump with the Walbro 255. It was a direct replacement!


    another win was that i was able to use my factory aluminum radiator. for radiator hoses i used the factory upper hose for a 2004 tahoe and i belive the factory 350 lower hose... ill need to double check that.

    I used a K&N air filter for a 2004 tahoe.

    I modified my factory battery tray to fit on the drivers side

    I used the k5 factory coolant resivior. I did hae t slightly modify the factory heater hoses though. ill get pics.


    this part is gunna suck...

    the motor i bought from BD Turnkey came with a modified wiring harness

    TRUCK - 1990 K5 Blazer

    Started With

    MOTOR - 350 TBI
    TRANSMISSION - 700r4

    New Stuff

    MOTOR - 5.3L from 2004 Tahoe
    TRANSMISSION - 4L60e from 2004 tahoe
    Last edited by jkroberts; 05-19-2015, 12:23 AM.
    Turbos. why have 1 when you can have 2?

  • #2
    Turbos. why have 1 when you can have 2?


    • #3

      Mel called me today and mentioned you need some type of wiring harness. I have some type of wiring harness. Will it fit what you need? I don't know but I thought I would ask and find out.

      I have an 85 2500 diesel suburban. YOu probably know that already. However, aside from the blown 6.2L Diesel, there was nothing wrong with the truck. Okay, a bit clapped out inside but when I started digging into it I was seriously contemplating scrapping my K5 body and transitioning over the 'burb. What does that have to do with a wiring harness? Well, like I said, I don't know what you need, but I have no problem pulling the harness out of the suburban to help you with your dilemma. I also have an 88 harness that isn't probably that much different, except it is TBI setup, which means it has the electronic control module.

      So, if there is anything I can salvage off of the burb that will fit your needs for the '90, let me know what it is. I will pull it out and you can take a look to see if it will work. A good description of the functions necessary for the harness would be of help as well.

      By the way, I did pick up a D60 in Minnesota in July while I was there. Had an option for a second but was just not sure what you wanted to pay for one or if you had already picked one up. Mine is out of an 88 1-ton and it is going to take some work to get back on the road, but hey, I am good with that. AS it turned out, I did not pull it home. It cost $175 to ship and 250 to rent a trailer. The bed was full so shipping ain't that bad and it is a no-brainer.

      Later. Let me know what is up with your harness needs.

      And by the way, if you are going to put in an LS motor, why not an L76. 6.2L aluminum block L92 head, and about 60 more horsepower at least. The come out of late '0X ESCALADES and HD2500 Chevy & GMC. Fit the same hole as the 5.3 as was well as same (E38?) computer setup. just saying.