boardmanMJ Posted February 15, 2014 Share Posted February 15, 2014 Although I'm still working on one MJ I'm starting to get ideas for my second, trail rig MJ. It was originally a 4.0 automatic 4x4 but the PO hacked the engine and wiring harness out. I'm thinking of going back to the V6 from early XJ/MJ instead of trying to mess with the fuel injection. So my questions are, what automatics were offered with the 2.8 and would it bolt up to my aw4? Link to comment Share on other sites More sharing options...
TheDirtyJeep401 Posted February 15, 2014 Share Posted February 15, 2014 2.8 have the same bolt pattern as a 2.5. AW4 other than an AMC v-8 I think they will only go with the 4.0 (not for sure) I'm not sure if I am reading this right, but are you wanting to swap in a 2.8? Link to comment Share on other sites More sharing options...
boardmanMJ Posted February 15, 2014 Author Share Posted February 15, 2014 Yes that is correct. It sounds crazy but I think it's the simplest way to go Link to comment Share on other sites More sharing options...
Spectormj Posted February 15, 2014 Share Posted February 15, 2014 the 2.8 in my honest thoughts cause ive got one UNDERPOWERED Link to comment Share on other sites More sharing options...
boardmanMJ Posted February 15, 2014 Author Share Posted February 15, 2014 That's what I was afraid you'd say. I'd like to keep something that originally came in a Comanche but I don't want to deal with fuel injection. Link to comment Share on other sites More sharing options...
Spectormj Posted February 15, 2014 Share Posted February 15, 2014 You and i have the mirror idea I'm going fuel injected you want carb i know my buddys cj had a v8 under the hood and that motor would pin ya back into the seat though sadly ther 2.8 at least as far as ive seen in the nashville area is underpowered on hills and not very get up n go Link to comment Share on other sites More sharing options...
Spectormj Posted February 15, 2014 Share Posted February 15, 2014 but also i have an 86 not quitew sure what year mj you got Link to comment Share on other sites More sharing options...
Eagle Posted February 15, 2014 Share Posted February 15, 2014 Yes that is correct. It sounds crazy but I think it's the simplest way to go Considering that it's a horrible engine that's not even heavy enough to be a good boat anchor, it's a terrible choice for you. And it's not even an easy swap, since your truck was originally set up for a 4.0L. It would be easy for you to get a complete wiring harness out of a wreck, and just go with the 4.0L again. If you really want to avoid EFI, get a Wrangler (or AMC) 4.2L, which was basically the same engine but with a longer stroke and a carburetor. Link to comment Share on other sites More sharing options...
Spectormj Posted February 15, 2014 Share Posted February 15, 2014 Yes that is correct. It sounds crazy but I think it's the simplest way to go Considering that it's a horrible engine that's not even heavy enough to be a good boat anchor, it's a terrible choice for you. And it's not even an easy swap, since your truck was originally set up for a 4.0L. It would be easy for you to get a complete wiring harness out of a wreck, and just go with the 4.0L again. If you really want to avoid EFI, get a Wrangler (or AMC) 4.2L, which was basically the same engine but with a longer stroke and a carburetor. :agree: there ya have it folks the all knowing Eagle :bowdown: and ive seen a dead hog with more get up and go than the 2.8 in my truck Link to comment Share on other sites More sharing options...
TheDirtyJeep401 Posted February 15, 2014 Share Posted February 15, 2014 4.2 would be a good choice. Even if you didn't want a 4.0 or 4.2, at least go with a 2.5. Its going to have more power than that 2.8 Link to comment Share on other sites More sharing options...
benjy_26 Posted February 16, 2014 Share Posted February 16, 2014 Yeah, the lack of a harness isn't enough of a reason to drop in a 2.8. I know it's not terribly popular in the Jeep world, but I've seen people get good results using a megasquirt system as a stand alone ECM for their Mazda Miatas and Toyota 4 bangers. I kind of want to use one on my L6 stroker, to be honest. Link to comment Share on other sites More sharing options...
FrankTheDog Posted February 16, 2014 Share Posted February 16, 2014 You can throw a 258/4.2 distributor on the 4.0 and I'm thinking make an adapter plate for a Rochester 2 Jet or weber carb on the intake. Run a GM one wire alternator and you would have an engine with very few wires. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted February 16, 2014 Share Posted February 16, 2014 I'm not sure, but I think the 4.2 head will bolt to the 4.0 block allowing the use of the carbed intake, or allow you to buy a 4 barrel intake for it. Someone might even chime in and say you just need the intake, but I'm not sure the ports will line up properly. I agree though it would be easier to just get new (used) engine and dash wiring harness to make what you have work properly. The 4.0 is a far superior engine. You would need a complete 2.8 donor to make that work. It will be less work and less money to just replace the wiring. The 2.8 (3.1, 3.4) swap would require the engine, A904 auto trans, transfer case, driveshafts front and rear, linkages.... how is this easier than replacing the wiring? Link to comment Share on other sites More sharing options...
boardmanMJ Posted March 2, 2014 Author Share Posted March 2, 2014 I know it's an old subject but I think I'm leaning more toward a YJ 4.2l to put inside the MJ. I also noticed in my newest 4WD catalog that they now offer the "EZ-EFI self tuning fuel injection system" for the CJ/YJ 4.2l with the in tank and in line fuel pump system. Looks pretty cool if you ask me. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted March 2, 2014 Share Posted March 2, 2014 You are crazy! For what youll be spending to get the YJ motor and then add a fuel injection system to it, you could buy a NICE complete running XJ donor and swap it all over to the MJ and do it RIGHT. Fot that money you could find a late model with OBDII and the updated front end and have a bonus sheet metal and door update with the engine and wiring... and interior too!!! I'm not trying to be mean, but what youre planning just doesnt make any sense. Sorry. Link to comment Share on other sites More sharing options...
jimoshel Posted March 2, 2014 Share Posted March 2, 2014 Yes that is correct. It sounds crazy but I think it's the simplest way to go Considering that it's a horrible engine that's not even heavy enough to be a good boat anchor, it's a terrible choice for you. And it's not even an easy swap, since your truck was originally set up for a 4.0L. It would be easy for you to get a complete wiring harness out of a wreck, and just go with the 4.0L again. If you really want to avoid EFI, get a Wrangler (or AMC) 4.2L, which was basically the same engine but with a longer stroke and a carburetor. I really hate to disagree with such a noted authority as Eagle, but in this case I feel I must. I have found the 2.8 to be an excellent boat anchor, provided the boat isn't to big, or the currant to swift. :thumbsup: Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted March 2, 2014 Share Posted March 2, 2014 Havent people put a 4.2 head on a 4.0 block ? If that's the case you keep you're driveline you would just need the head manifold etc from the 4.2 . Link to comment Share on other sites More sharing options...
boardmanMJ Posted March 3, 2014 Author Share Posted March 3, 2014 I'm not saying I'm going to add the EFI because I really want to keep things cost effective and simple. The YJ motor I'm not really worried about I can get my hands on one. If it's the case where I could just bolt the 4.2 head on the 4.0 block that would be the best way to go for me. I have the transmission, transfercase, and driveshafts I'm just missing the motor. Link to comment Share on other sites More sharing options...
FrankTheDog Posted March 3, 2014 Share Posted March 3, 2014 If you want cost effective buy a rotted out XJ and swap the wiring and drivetrain over. They're out there. I've been DDing a 96 for the last 1.5 years that I bought for $100. All I've done to it was put tires on it and a radiator I had laying around and a new water pump. 40,000 miles so far. That's not a bad return on my investment. Link to comment Share on other sites More sharing options...
carnuck Posted March 5, 2014 Share Posted March 5, 2014 I put a 4.0L in place of the 4.2L in my '84 J10 along with an AW4. To get it so I can drive it to town from my cabin I built an adapter to bolt a spare MC2100 to the EFI intake. The injectors stay in place. I ran out of time last summer and the road had a landslide in Dec so it awaits a month or so that I can get up there. GM HEI dist with AMC gear on it and electric fuel pump. Later it will be LPG powered. Link to comment Share on other sites More sharing options...
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