2.5 to 3.4 info wanted

[cardiff]

Hello

I know it's not an MJ, but I have been told some of you guys may be able to help.

I have an 84 xj with ax5 and a 2.5 which has finally blown. I'm looking for info on swaping in a gm 3.4. Does anyone know where I can get engine mounts, or are there ones I can find at my wrecker's that will do it? What kind of fabrication would be involved? I just want to go into this with creating the least amount of headaches for myself as possible. Also to be back behind the wheel as soon as possible, with some much needed power for larger tyres.

Thank you

Marc

[mvusse]

Engine mounts from a 2.8 V6 in a 84 through 86 XJ or 86 MJ should work.

 

Actually, pretty much everything from that 2.8 should work. Probably be best to find a parts car so you have a reference as well as all the little parts. When you're done, part out what's left to recover your money.

[dasbulliwagen]

If youre looking for quick and easy, this isnt it. It would be if you already had a 2.8 V6 in your truck, that way all you would have is a long block swap, but changing from a 4 cyl to a V6 will be a lot more work. If you had a complete donor vehicle sitting next to yours with everything you needed to swap, that would be better, but if youre relying on junk yard trips to get parts, its going to take you forever.... not to mention finding a JY donor in the 84-86 range that hasnt been picked over yet, and a junkyard donor 3.1 or 3.4. It might be easier to find a late model 2.5 with port injection, and swap in the engine and accessories, intake and exhaust, with the engine compartment harness, and dash harness and computer and fuel pump assy. This will give you a bunch more horsepower than the carbed 2.5 and be much simpler than converting from a 2.5 to a 3.4. Converting can be done, but it will be more difficult and time consuming, and it sonds like youre trying to stay away from that. Let us know what you figure out! Good luck.

[Eagle]

I agree with the above. You can get the motor mounts and such from a 2.8L XJ or MJ (1984-1986), but the 2.8L was carbureted, not fuel injected. Other than motor mounts, manifolds, and brackets, not much elese will work. And you can't use the 2.8L flywheel. The 2.8L was externally balanced -- meaning the flywheel has an eccentric weight on it. By the time GM got around to the 3.1/3.4L engines, they had that figured out and the flywheels were neutrally balanced. To use a 2.8L flywheel, you can send it to a shop and have the eccentric weight cut off and the flywheel rebalanced. If you have an automatic, you have to figure out a way to get a torque converter neutral balanced.

 

A late model, multi-port 2.5L will not equal the horsepower of a 3.4L V-6, but overall would be a big step up from your throttle body 2.5L and probably easier to accomplish overall.

[dasbulliwagen]

The 84 and 85 2.5's were carbed as far as I know, so upping to a port injection systme from 91 or newer would be a good step up.

[bmaley79]

So I have already went through all of this. The motor mounts are all the same doesnt matter if it is a 2.5, 2.8, or 3.4. They are all drop in the mounts. The fly wheels are diffrent and the wiring and fuel pump setup is diffrent. and the computers are diffrent. I switched mine out in less than 5 hours. The switch is really easy. And the hourse power gain is worth the time to switch.

[mvusse]

Are you POSITIVE the AMC 2.5 and GM 2.8/3.1/3.4 use the same mounts?

[cardiff]

Hey. Thank you for the info. I have access to the 3.4, computer with wiring harness, alredy have a 4.0 rad, plus mid 90's fuel tank with efi pump, and have a full shop. I could easily do a newer 2.5 and computer, but I live in the mountains and hate being at half the speed limit for most the way home from work. I know the 2.8 flywheel works once it is rebalanced, does the 2.5 flywheel work?

thanks marc