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krustyballer16

Cummins B3.3 Powered Mj Build!

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how much firewall choppin did you have to do?

Ive got a buddy of mine in west tn who can get me the 4bt and i need to figure out how easly i can make it fit an 86

If you are trying to put a 4bt in I would think firewall mods would be the least of your worries......

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I didn't have to do any firewall mods. Mine is a 3.3 not at 3.9 (4b). Mine is way smaller...a 4b is like 6" taller and wider and longer. I think it would be a lot harder than what I'm doing. But it's been done. Might be a build on here of it.

how much firewall choppin did you have to do?

Ive got a buddy of mine in west tn who can get me the 4bt and i need to figure out how easly i can make it fit an 86

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A 4bt is honestly too much engine for a truck that's not much over a ton and a half in weight. You have to reinforce the 'frame' in the engine bay, and then you have the rest of the cab's unibody frame to worry about, put significant lift on just so the engine might fit, and you may or may not have to modify the oil pan. After all that you have the rest of the drivetrain to replace. If you got it done your front end will be stupidly heavier than the rest of the truck, making offroading not fun (MJs rear ends are very light to begin with and that engine will only exacerbate that issue). Cummins 3.3s on the other hand are not a lot heavier than the I6, don't necessarily have to beef up the frame, and their torquey power will more than thrill you I'm sure. Plus you can use the rest of the drivetrain without worrying too much about tearing it apart. Though I personally would probably upgrade my axles.

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How much would a 3.3 run?

A brand new "long block" 3.3 on eBay runs like $3000-5000 then finding parts for it will be expensive! Theres sometimes some on craigslist used for $1500-3000 for a complete running engine. they're not as common as 4bsI found mine on craigslist a couple hours away, 2 engines (one complete the other 80% there), one turbo'd the other not, for $4400. If you don't know anything about diesels or never done any motor swaps or fab work, this probably isn't the way to go. It's not easy or cheap. I'll have about a year and $8000 in this swap...

 

4b might be cheaper since it's more common but the fab work is gonna be about the same if not harder.

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A 4bt is honestly too much engine for a truck that's not much over a ton and a half in weight. You have to reinforce the 'frame' in the engine bay, and then you have the rest of the cab's unibody frame to worry about, put significant lift on just so the engine might fit, and you may or may not have to modify the oil pan. After all that you have the rest of the drivetrain to replace. If you got it done your front end will be stupidly heavier than the rest of the truck, making offroading not fun (MJs rear ends are very light to begin with and that engine will only exacerbate that issue). Cummins 3.3s on the other hand are not a lot heavier than the I6, don't necessarily have to beef up the frame, and their torquey power will more than thrill you I'm sure. Plus you can use the rest of the drivetrain without worrying too much about tearing it apart. Though I personally would probably upgrade my axles.

Basically...I'm doing mine as a daily driver. I think for a play toy, a 3.3 or 3.9 Cummins should go in something a little bigger or different ...

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I think a 3.3 would be only ok for a play toy. Slightly front-end heavy. What I'd like to do with an MJ is: Long-bed metric ton, D44s front and rear, Cummins 3.3. Bigger tires but not much lift. I'd like it for a 'work truck'. Hauler if you will. I have a short box MJ and don't wheel it, in fact it would break my heart to damage that body, so, I'd rather have a more useful MJ, and a diesel with good axles would fit my bill.

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I think a 3.3 would be only ok for a play toy. Slightly front-end heavy. What I'd like to do with an MJ is: Long-bed metric ton, D44s front and rear, Cummins 3.3. Bigger tires but not much lift. I'd like it for a 'work truck'. Hauler if you will. I have a short box MJ and don't wheel it, in fact it would break my heart to damage that body, so, I'd rather have a more useful MJ, and a diesel with good axles would fit my bill.

I don't consider a work truck or hauler a play toy. Your setup would be sweet to do. But that's what we got our J10 for now. There's so many different setups I wanna do with a Comanche!!

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I think a 3.3 would be only ok for a play toy. Slightly front-end heavy. What I'd like to do with an MJ is: Long-bed metric ton, D44s front and rear, Cummins 3.3. Bigger tires but not much lift. I'd like it for a 'work truck'. Hauler if you will. I have a short box MJ and don't wheel it, in fact it would break my heart to damage that body, so, I'd rather have a more useful MJ, and a diesel with good axles would fit my bill.

I don't consider a work truck or hauler a play toy. Your setup would be sweet to do. But that's what we got our J10 for now. There's so many different setups I wanna do with a Comanche!!

 

Bad wording. I don't consider a work truck or hauler a play toy either. What I meant was: No, I wouldn't use a 3.3 for an offroader. In an MJ anyway. What I would do with it is...etc,etc,etc. And yeah, I'd LOVE a '62-'70 Gladiator. I'd put a diesel in it as well. 

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Best conversion I've seen is a VW TDI (weight, power, size, drivability).  Although this little guy is gonna be nice in the no-electronics dept.

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found a power steering pump and got it mounted! pump came off of a late 80s dodge 150 pick up or whatever they were back then.

 

 

brackets for power steering and water pump pulley powdercoated. 

 

 

mounted fuel filter too, right behind power steering. its about 4 inches lower and more to the drivers side than it was originally.

 

ordered a couple silicon 90*s and a 45* for my turbo/intake piping to run behind the motor. 

we decided not to run an intercooler. didnt really have room and would be more difficult than it was worth we thought. 

 

will be ordering all my lines and fittings for my fuel filter to pump, turbo oil lines and alternator oil lines tonight. 

 

exhaust is scheduled for a month from now so ive got a "deadline" now to get it set in the truck and running. 

 

almost there!!!!! 

still have speedo, throttle cable, gauges, lift, and a couple other little things to do. 

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back side power steering bracket. 

 

were gonna run the radiator hose from the water pump down and through the power steering brackets. (will have metal pipe between the 2 brackets so we can make our own house go where we need it. 

 

started working on turbo piping this week. made a plate to block off where it went originally, into the top of the maifold and over the top of the motor. 

 

made a new plate with a 2" hole to replace the solid plate on the back side of the manifold.

 

new plate with the original piping cut down to hug the back of the motor. it will be cut down right where it 45s downwards and a silicon 45 will be put in there facing more level toward the turbo in the front 

 

got my block heater installed. i cut a 1/4" plate with a 1" hole in it and welded a pipe union fitting cut in half onto it. fits perfectly. 

 

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Man, you're killing me... I'm freaking jealous lol.

You're doing an excellent job though, especially with the picture documentation.  Glad to see it's coming along.

 

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Started it up yesterday for the first time in the truck! Starts right up, no leaks. Butttt .... Won't get above 1100 rpms. Runs rough. Blows white smoke. We swapped injectors out of the other motor I have and no difference really. Were gonna make sure it's not outta time in the morning and go from there. If it's in time I guess were gonna try to make our own injector tester and go from there. It purrs like a kitten now tho, just at low rpms. And also, it won't get up to temp. It's only gotten to 160* after running about 30 min. We've put an hour total on it since yesterday...

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Awesome work dude :thumbsup: The power steering belt looks a bit funky ...Long might need a idler ? 

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Awesome work dude :thumbsup: The power steering belt looks a bit funky ...Long might need a idler ? 

thanks man. and power steering belt is fine. all works good and no problems. we finally got the motor to idle a lot better and run smoother. we had to turn the fuel screw on the injection pump up. it wasnt set right to ever run or whatever since it was a show motor or wasnt ever in anything. now we have waaaay less white smoke and a haze of black smoke. still doesnt run 100% right but its getting there. weve got higher rpms, 1650, still not what we should be at. and still takes a bit to get up to temp. gonna take a set of injectors to the diesel shop today and have them tested. bought my battery too, an Autocraft AGM H8. pretty massive battery. and going to buy 10 feet of both cables for it today.

 

and i forgot to say earlier, we ripped ALL the wiring out and bought a summit complete wiring harness kit and my dad has been doing all the wiring in the truck. just a few more wires to hook up; radio, windows, locks, headlights, dome lights, fans. my dads doing all the wiring, id be lost with all of it even though its all marked and has a booklet with it.

 

gonna be working on cutting out all the rust in the frame and fixing it this week so we can start installing the lift next week or weekend! :driving:  

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Man, this build is so nasty!!

I'm extremely jealous haha.

 

i've been kinda sitting here waiting for more to come,

i just couldn't help to go ahead and comment on it!

 

I have a common rail cummins, and it's been a dream to throw one into my comanche.

i saw the posting about the 4bt, and thats what i would really like to do...

maybe this motor would work better, i still have some saving to do and life left in my I6..

my cummins swap won't be anytime soon, and still need to learn the fab work.

 

again man, sick build.

TRULY JEALOUS!!

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when we first started it up in the truck it was just blowing white smoke so we figured it was a fuel issue. had the injectors pop tested and one wouldnt open but once it was tested it worked fine. we had turned the fuel way up thinking we needed more fuel and once we got the injectors working right we turned it back down (pic of black smoke was with fuel way up) and it just barely smokes now. have it idling at 850 rpms.

 

built an aluminum overflow bottle for the radiator 

 

in the process of building a battery/ storage box for the bed. right now i just have the battery in a plastic toolbox in the bed. 

 

 

now the truck smokes white/blue when you start it up after it sits for a couple hours. thinking its valve stem seals. i got them with the gasket set i ordered last year so ill look into changing them in a couple weeks. 

 

a-pillar pod and you can kinda see the tach below it and to the right. 

 

hood hit a little on the heater hoses so had to do a little rough trimming. itll work for now until were ready for final body work. 

 

mounted my shift console. for some reason it didnt mount up right. when it was screwed in at the 4x4 shifter it didnt line up with the mounting tab on the plate on the tranny tunnel. so i had to drill the rivets out and move the tab over. then with no carpet, the console moves around pretty freely front to back while shifting so we had some edge trim laying around so we threw it on around the bottom. works great.

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