I6 to 6.7L LQ4 with standalone fuel/spark? - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > Engine Tunes/Mods

Engine Tunes/Mods Performance Engine Tuning/Engine Modifications

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Old 11-01-2018, 01:04 PM
TheRepoMan TheRepoMan is offline
Junior Member
2002 Chevy TrailBlazer LTZ
Fire Red 4.2L I6 2WD
Join Date: Sep 2018
Location: Arizona
Posts: 4
I6 to 6.7L LQ4 with standalone fuel/spark?

I have an 02 LTZ I6 as my (now) DD and now just got an 03 LTZ 2WD with a I6 that has a rod through the block. My plan for this 03 is to swap in an engine I was using in my '73 C/K which is an LQ4 that's been stroked to 6.7L. (Drunk driver hit me and totaled it)

The engine also has MSD 6LS ignition/coils and a full MSD Atomic EFI with an MSD Airforce intake and MSD Throttle body. I spent a pretty penny on this engine so I'd really like to be able to use it. It only has 16k miles on it since built. I also have 2 walbro 255 fuel pumps and 1000cc injectors.

I also have a 4L80-E with a 3000 stall that was in the C/K that's controlled by an MSD transmission controller, I know this probably won't fit can I do anything I can do to make it fit? It only has 16k miles on it since it got built by Mad Dog transmissions. Perhaps I'll just sell it and buy a 4L60-E from them.

I've read on many other swap posts that I'll need new transmission mounts and a harness. My goal is to get rid of as much GM computer interference as I can. What else am I going to need? Will this engine even fit right?

I have a great driveshaft guy that can shorten the DS if needed along with a good fabrication dude.

So apart from engine mounts/AC Relocation/Trans mounts and wiring what else is needed? I would just go buy another C/K but I don't like how I fit in them so I'm on the hunt for a new project. My end goal is a sleeper Trail Blazer or my plan B will be a 1st gen 2 door Tahoe.

Thanks all!!
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Old 11-01-2018, 05:50 PM
astroracer astroracer is offline
Junior Member
2008 GMC Envoy Denali
Carbon Black Metallic 5.3L V8 4X4
Join Date: Aug 2018
Location: Mid-Michigan
Posts: 75
The LQ4 will bolt right in on 5.3 engine mounts. I don't know how much difference there is between the I6 and the V8 LS mounts to make a recommendation as to being able to use those...
If you compare the 4L80 to the 4L60 in your donor truck you can get a good idea as to how it will fit in the tunnel. We know there isn't much room around the 4L60 so you might have quite a time getting the big guy in there.
The wiring is the hard point. So many systems in these trucks run through the ECM, TCM and BCM that getting a new ECM from a V8 TB or Envoy may be your best direction. There are a number of companies that offer reprogramming for these trucks so contacting a couple of those would be my first recourse. I would contact PCM of NC and get their take.
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Old 11-08-2018, 10:51 AM
mesprime mesprime is offline
Junior Member
2002 GMC Envoy SLT
Pewter Metallic 4.2L I6 2WD
Join Date: May 2008
Location: Atlanta, GA
Posts: 10
Does the MSD Throttle body support non-accelerator cable installations? Your TB does not have a mechanical accelerator cable as the OEM throttle body is controlled entirely by the PCM. You would need to either replace the existing drive-by-wire accelerator pedal with a mechanical one or somehow interface the existing one to the MSD Throttle body.
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