2.8 or 3.4

[gorillaxj]

i have an 85 xj with 125000 miles on the original 2.8l and manual trans. it was given to me with no payment other then registration(so no chioce of the 4.0). i put a 4.5 inch lift and 31s on it and have heard lots of horror stories about this motor. i was wondering what peoples experiences with this engine are...... and conversion...... any comments will help. thanks

 

[BlackDog]

I would say drive it til it causes you grief and then vortec 350 that little guy.

In my humble opinion GM's 3 worst motors were the 5.7 diesel, Caddy 4.1, and the 2.8, which they shared with AMC only to prevent AMC from being competition, I think.

The one that I had in my XJ ran okay, but I was happier with the 2.5 in my Comanche.

 

[waynehartwig]

I had an 84 XJ with that motor in it... 220,000 miles when I donated it to the Sacramento for Kids program. It ran ok, never did anything major to the motor, gutless as heck though! I could BARELY pull my boat the trailer speed limit of 55! Shoot...Even without towing anything I was lucky to cruise the speed limit... Off road it did very well though... The 4 low and auto worked pretty well together.

 

[crimsonride]

Yep, no doubt that 2.8 is a pile of dump. I've swaped in the 3.4 complete with the fuel injection and all and I'm very happy with it. It was a learning process though as I couldn't find anyone that had kept the MPFI but it looked so good I just couldn't pull it off and put all the old crap back on it.

Everyone I know swaps everything over to the 3.4 block, even the oil pan and accessories. I just didn't want to do that.

Oh, man, there were lots of little things that I can't remember all of right now. A few things are you won't be able to have AC. There's no room for the pump, it wants to be right where the motormount is. You have to fab a few small parts for the throttle cable and add some sensors for the dash guages, the computer needs the sensors in the motor and they're not the same for the jeep. I had to have a new Y pipe fitted up since the oil pan is about 1" deeper and the old pipe wouldn't wrap around it.

I'm pretty happy with the engine. It's super smooth, fires right up with the fuel injection. It's totally different to wheel in a vehicle that runs at all angles, the old engine would be sputtering and puffing while I was trying to climb something. That and it's a major power improvement.

There's a lot more I can tell ya but I'd have to go back and read some of my old emails.

let me know what you want to know.

 

[BlackDog]

What kind of horse does that 3.4 make as you have it set up?
And is the bp compatible with the 2.5?
And how much did the swap cost?

 

[crimsonride]

Stock the 3.4 puts out 2.5 ft/lbs of torque and 160 hp. I'm hoping I've got 180 with a complete exhaust and intake.

I think everything all together I'm about $1200 or so for the swap, that's $500 for the motor, $400 for the wiring to be modified and various other things like a computer, hoses, plugs and wires, air filter, air hose, new motormounts, new fuel pump. I guess it could be a little more than that. I bought a new radiator but that's not necessary.

 

[gorillaxj]

whats the difference in gas mileage between the two motors?

 

[74highboy]

just drive it till it blows then buy a new one its a jeep

 

[crimsonride]

Well, considering I was getting between 7 and 8 from the 2.8 (don't ask me how) and after the swap I was getting around 12-13 it's a pretty good improvement. I think it's changed and I can tell you in a week what it gets, I haven't been keeping track but I made note of the miles last fillup and tried the acetone in the gas as described in the other thread on this forum so I can tell you when this tank is empty. My jeep needs regeared so it's not going to get great mileage with the 33's.

The best part is not having to floor it on the freeway and hope you go the speedlimit, being able to drive up a canyon is also a bonus.

It's nice to have passing power and be able to back off the gas when driving on the freeway. Acceleration has greatly improved. It's not a rocket but it certainly is a big improvement and is plenty fast for my needs. I haven't worked out a kick down cable and I think my tranny needs replaced. I have to hold it in gear till I want to shift then bump it up a gear. Not a big deal but I need to work something out to take care of that.

 

[gorillaxj]

thanks for the help. you awnserd my questions.