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Thread: '86 Comanche Long bed, Slow build...

  1. #1
    Join Date
    May 2011
    Location
    Mancos, CO
    Posts
    1,163

    Default '86 Comanche Long bed, Slow build...

    12/13/17 Update: I know Photobucket issues cause most of you not to be able to see the pictures. There IS a workaround for some browsers!! Search "photobucket hotlink fix". You'll see apps for Firefox and Chrome. If you're not using one of those two browsers, you need to start. Click the "install" button and voila, pictures show up!
    Enjoy,
    Chris



    Well, I've been debating whether to post some build details and ideas here, or on some sort of Jeep forum... I decided that this is the place, at least for now, since I don't belong to any Jeep forums...

    I have been lusting after a Comanche for quite a while, and finally bumbled onto an '86 last summer for $700. It is an '86, and the 2.8L has 225k miles on it, and wasn't running right. (Starts great, but runs worse and worse as it warms up.) My theory was that it busted a crank, or has split pistons or something. Guy says it started running like crap during an emissions test in CO. It's a Colorado vehicle at least most of it's life, so there is little rust, which was the clincher for me! I drove it about 25 miles home at 35mph because that's pretty much as fast as it would go.



    Based on firewall mods needed to put a 4.0L in an '86 Comanche, I decided almost immediately that the easiest engine swap was a 3.4L from a '94/95 Camaro. Of course I wanted Fuel Injection too, and I found an engine on Craigslist that would come with all accessories, harness, and computer for $300. I dumped the 3.4 in the bed and let it sit for almost a year while I moved.


    I considered for a short while finding a 4.8L V8 and tossing that in, but then I'd need lots of expensive adapters, a new trans and whatever else goes with that, and a big radiator, exhaust, etc... The Comanche is light, so I'm hoping for a little better fuel economy from the 3.4L anyway!

    I prepped the 3.4L by pressure washing it and identifying all needed wiring connections for the GM computer, and labeling them.


    I also put some stuff back together that the idiot I got if from started to take apart for no reason. (Lots of missing bolts that I had to get from the junkyard...) What are some people thinking?? I stripped off the air injection tube, but left the EGR for now so I don't need to reprogram the computer. Here's the 3.4L ready for motor mount transfer...


    Time to pull the 2.8L out of there!! Look at all that emissions junk!! According to the label, this is a "high altitude" emissions truck. Not sure if that means it's more like CA, or FED, but at least it doesn't have a computer controlled carb!


    And its out!!


    Look what I found in the bellhousing!!


    More in a bit...
    Last edited by 1stDeuce; 12-13-2017 at 03:36 PM.
    '06 GMC K2500 CCSB D/A w/ '94 Hallmark Ute 8.5'
    '86 Jeep Comanche
    '00ish Jeep TJ Scrambler
    '99 XR400R
    I'm my own boss now, I do what I want!!!
    KB9SCX

  2. #2
    Join Date
    May 2011
    Location
    Mancos, CO
    Posts
    1,163

    Default Problems...

    Well, I pulled the motor mounts off the 2.8 and the driver's side bracket bolted right onto the 3.4L. On the pass side, I was not so lucky... First, the knock sensor on the 3.4L is right in the way of the 2.8 motor mount. Swapped it for the block drain plug lower and farther back on the block and resolved that problem. (It should still work fine from what I've read.)
    (You can see the plug where the knock sensor was, just left of the top of the motor mount, and the knock sensor in it's new location at the lower back of the block, behind what I think is the crank position sensor.)



    Then I realized that the A/C compressor was ALSO in the way. Evidently the Camaro motor mounts are lower and farther back on the block than the Jeep mounts. (I don't have them, but I may watch for the right one to see if I can use it instead...) I pulled the A/C compressor and its rear bracket, and the mount finally bolted up.
    (Compressor is about 2" too long. )

    Then I realized that the Camaro flywheel is a deep, dished design, whereas the 2.8L flywheel is flat, like you normally see. Mind you, it's not heavier, just dished and hollow. Not sure why GM did this...
    (Jeep 2.8L flywheel still on the engine, thick Camaro flywheel in my hand.)


    But I couldn't use the '86 2.8L flywheel because it's externally balanced. I could either have it machined and re-balanced, or get a later 2.8L flywheel for an S-10. (They switched to internally balanced somewhere around '88) Since a new one was only $60, I ordered it up! I'm hoping that the Comanche clutch will bolt up, as it looks fairly new.

    For now, I'll just run it without the A/C pump. The truck is missing all the rest of the underhood A/C stuff anyway. If I get excited about A/C, perhaps I'll be able to figure out a pump that will fit and work and get it all plumbed up.

    Next up: cleaning up the under hood wiring mess...
    Last edited by 1stDeuce; 07-15-2015 at 04:53 AM.
    '06 GMC K2500 CCSB D/A w/ '94 Hallmark Ute 8.5'
    '86 Jeep Comanche
    '00ish Jeep TJ Scrambler
    '99 XR400R
    I'm my own boss now, I do what I want!!!
    KB9SCX

  3. #3
    Join Date
    Apr 2008
    Location
    ON, Canada
    Posts
    2,205
    Oh man... just sell the the 3.4 and get a 4.0! Use it as an excuse to get a ready built stroker and don't look back.

    My MJ came from Colorado as well. It's so nice when everything comes apart without applying heat or extreme measures. Little bit of wire wheel on the floor and some primer and my MJ is ready for top coat inside and out. Such a change from what I'm used to.

  4. #4
    Join Date
    Jan 2006
    Location
    Reno, NV
    Posts
    1,560
    I too have a soft spot for MJ's, so I will be watching to see where this one goes.

    Jack
    2007 2500hd, Max/Alli, Hawk FWC (the new explorer)
    Build thread: http://www.expeditionportal.com/foru...07-Chevy-Build
    2006 Jeep LJ Rubicon-Sold
    1985 4Runner 22rte-Project...
    KE7NCK

  5. #5
    Join Date
    Feb 2014
    Location
    Omaha, Ne.
    Posts
    6
    Sweet truck. It will be worth the effort.

  6. #6
    Join Date
    May 2011
    Location
    Mancos, CO
    Posts
    1,163
    Already have the 3.4L so not doing a 4.0L. (My TJ is waiting for me to get the 4.5L stroker project underway.) This truck is just going to be a driver!! I'm hoping it'll get good mileage, and since it weighs less than a Camaro, it should get around quite well! I have a big truck if I need to get more done.

    Flywheel came in a few days ago and it all bolted up, using the clutch that was in the Comanche on the 2.8L, so the engine is ready to go back in!

    Ripped all the split loom off the underhood wiring and started sorting out what I needed and what could go.


    Looks like the Comanche barfed up it's dinner when I was done...


    Much less mess underhood, and I know what everything that's left does.


    Used a BlueSea fuse box and a distribution block from an early 90's Chevy truck. Added relays for switched ignition and fuel pump up by the fuse block, and fan control down in front.


    Just about as far as I can go without the engine and harness in place, so time to toss the 3.4L in!!

    About time for another junkyard run... I'm planning to use a 2-speed Taurus fan, with low being on anytime the engine is running, and high controlled by the computer. Saw a new radiator in a junker last time I was there, so I'll be picking that up too! And an instrument cluster with a tach to see if I can get that working. (Hopefully it will be OK with the GM tach signal...)

    Once it's all together and working, I'll put it back in split loom and it should look pretty clean.
    Last edited by 1stDeuce; 07-15-2015 at 05:05 AM.
    '06 GMC K2500 CCSB D/A w/ '94 Hallmark Ute 8.5'
    '86 Jeep Comanche
    '00ish Jeep TJ Scrambler
    '99 XR400R
    I'm my own boss now, I do what I want!!!
    KB9SCX

  7. #7
    Join Date
    Dec 2011
    Location
    Albuquerque, New Mexico
    Posts
    421
    I too have a soft spot for the Manche. I want to find one once we get out to New Mexico. Awesome truck and its a Jeep. Great job so far and will follow the thread.
    A decent build up Of a 92 Dodge dakota.
    Leave no Trace instructor

  8. #8
    about a month ago, there was a wildernest for a longbed MJ up on the Reno CL, not sure if its still available. also, check in over at comancheclub.com!

  9. #9
    Join Date
    May 2011
    Location
    Mancos, CO
    Posts
    1,163
    Took last week off as I was out of town, but I managed to drop in the 3.4L before I left... Back to it now!!

    I finished the important wiring last night. Still need to swap in the XJ fuel pump that I bought and run a 12v wire for the pump down from the relay. Then put the starter in, hook up the fuel lines, toss in the battery, and see if it runs!! If it does, and doesn't sound like I paid $300 too much for it, I'll get it an idler and serp belt, put a radiator in it, and wire up the rest of the non-essentials. (Gauges, CEL, Clutch and brake switches, and cruise control)



    Time for a junkyard run at lunch today too!! I love the junkyard here!!!
    Last edited by 1stDeuce; 07-15-2015 at 05:06 AM.
    '06 GMC K2500 CCSB D/A w/ '94 Hallmark Ute 8.5'
    '86 Jeep Comanche
    '00ish Jeep TJ Scrambler
    '99 XR400R
    I'm my own boss now, I do what I want!!!
    KB9SCX

  10. #10
    Join Date
    May 2007
    Location
    Kuna Idaho
    Posts
    720
    Lookin good. I'm interested to see it run and how the performance is

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