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1994 GMC TBI 454 swap out to 2004 6.0 or 2002 - 8.1L

Discussion in 'Engine Swaps & Builds' started by ob3135, Dec 19, 2014.

  1. ob3135

    ob3135 I'm NEW... What now?

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    Hi all.... Well, I guess I'm asking for starters which way you all would go... I just finished converting a 1969 ford to a 5.9 cummins and my next project is to do a conversion on my pulling truck. It's a PIG! I love the truck though. So it's a 1994 GMC 1 ton with a 7.4L 454 tbi in it. It gets a wapping 8 to 10 mpg but mostly 8... Sooo, I figure if I'm already sucking down that kind of fuel I may as well get some bang for my buck and this tired old restricted 454 just isnt doing it.

    I have a ling on a couple drive trains. One is a 2002 - GM 8.1L vortec engine - trans - transfer case - all computer - wiring harness etc... Basically a donor truck with only 42K miles on it. Not sure how but thats all it has...

    The other one is a entire drive train and all wiring / ECM etc... It's a 2004 GM 6.0L small block, I can get the pedal (considering it's electronic controlled throttle adjustment instead of mechanical cable) So it's all there.

    (1) I just wonder first of all I get a sneaky feeling the components and set up of the 8.1L engine ecm / electronics are going to be significantly easier to manage but I could be dead wrong on that...

    (2) I also believe the 6.0 would get substantially better fuel economy, but you tell me if I'm wrong on that to, I'm sure someone out here has experience with both?

    (3) Is a 2004 version of that 6.0L going to have the V.V.T or cam phasing tech in it and if so will I have any issues with that aspect, I think if my knowledge of it is correct that the workings of the VVT are all internal accept the sensor from the electromagnet on the timing cover back to the ECM. So does that mean the VVT aspect is irrelevant as far as complications in the conversion?

    (4) Is the power / torque of the 8.1L really that much better than the 6.0l or is the high winding ability of the 6.0 being a small block better over all even with less power?

    (5) Does anyone have experience going from a Transmission that does not have a "Tow/Haul" mode and installing one that does, I'll have the donor truck, anything I need, i know I'll have to put the right shift lever in the column and get the plug from the to the control unit. Any insight into the hidden grimmlens of doing that? Cause I could get an adapter plate made and go with a monster Trans version of the trans I am currently running...

    So, what say you? I know , I know, everyone is going to be very very tempted to say, come on you dumb ass, just go buy another truck with the engine you want :) But I own a shop, we do diesel conversions, and any of these cool projects I do are first of all "FUN" (I put it in quotes cause sometimes it aint), they give us good marketing material, get to show it off to potential clients, we learn, and most of all I get to keep my old body style dually that I love, and have the drive train I want.

    (Well, with one exception, I'd like to put an Allison behind it, but lets not jump all the way off this ledge :)

    So I know that was a lot, but hey, thats why we come out here right? Get those damn gears smoking in the knoggin and throw something at ya we can really tank into the deep brain cells about :dunno:
     
  2. OldCracker29

    OldCracker29 I've been knocked down drug out and left for dead

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    The 6.0 is an awesome engine, but my 2001 doesn't get very good gas mileage. I have a buddy who had an '05 with a 6.0 and it didn't do much better. :dunno:
    :welcome:
     
  3. PenguinLTZ

    PenguinLTZ I'm too LAZY to Choose a Custom Title!!!

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    I have had them all. 8-10 with the big blocks, 10-12 with the 6.0

    I would take a later model 6.0 over a 7.4, but my 8.1 was a beast with exhaust.

    6.0s can be hot rods, but if you don't want to screw around with performance parts, and have that donor lined up, get the 8.1 and everything behind it. I have missed my 8.1 since the day we parted.
     
  4. ob3135

    ob3135 I'm NEW... What now?

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    Yea I been thinking the 8.1 might be the way to go.
     
  5. ob3135

    ob3135 I'm NEW... What now?

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    Anyone out here have any experience with the conversion?
     
  6. ksblacksilvy

    ksblacksilvy Business up front

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    What you want to do isn't impossible, and has been done on similar vehicles... Have seen 8.1's swapped into older vehicles than yours. Most of it is fabbing stuff to fit, and wiring... Pacific Fab is the place to talk to if you don't want to do it all yourself. It's definitely doable, will just take time, patience, and some $.

    Go with the 8.1. They're beasts.
     
  7. ob3135

    ob3135 I'm NEW... What now?

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    That seems to be what most folks think, is that the 8.1 is a monster.

    I've done some pretty intense conversions so I'm fairly familiar with the process.
    Just worried about wiring mainly. Sensors. Gauges, etc. I've mostly cummins conversions into older Riggs, old 12 valve cummins. Almost zero wiring issues. So ecm / tcm / wiring is my main concern.
     
  8. cRiPpLe_rOoStEr

    cRiPpLe_rOoStEr We don't ride to provide a good story for the rice

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    Even if the 6.0 could fit your requirements, the 8.1 is just too cool to leave behind.
     
  9. ksblacksilvy

    ksblacksilvy Business up front

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    Yeah the wiring will be a lot more intensive than the 3 wires you need to hook up for a cummins. But if you have everything and experience you'll definitely be able to do it.

    Here's a cool 8.1 swap:
    1978 Chevy K10 Pickup - Capable Classic Camper
     

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