Topic: Swapping 2.5's

[ragincajun]

I have 2 long blocks right now.  I have the 89 original engine w/180K+ on it, and a 91 engine w/102K+ on it.


My question is can I interchange these engines?

I have an 89YJ, which is TBI, from my understanding the 91 is MPFI.  How will this work if I want to replace the 89 engine with the 91 engine?  Computer issues?  Nutter?

Also I plan on rebuilding one of them much the same way as YJmechanic did to his.  Which block would be better to build the TBI, or MPFI, or should I look for an even later model block.  I know where a 97 is cheap.

[wrangler387]

I'm pretty sure you can just swap all of your TBI stuff onto the MPFI block and then drop it in. Don't quote me on this, because i havn't seen a TBI motor.

[supryj4]

I am not sure what you are looking to do.Are you trying to convert to the MPI or are you just going to use the engine

[Jeffy]

The blocks are the same.  If you want to fill your plate, then you can swap over to MPFI but it's not that simple.  THe easiest swap would be to get the engine out of a late model YJ.  Then you can take the gauges and dash harness and not have any problems.  You'd basically scavenge everything off the YJ.  Engine, engine harness, exhaust, fuel lines, gas tank, computer, bulkhead plug dash harness, gauges, VSS, etc....  Swapping over to later gauges will be easier then trying to match pins for the old stuff to the new.

[supryj4]

I bought a 94 that was in an accedent removed the whole wireing harnes and installed it in my 90 along with intake, gages,computer,etc the fuel lines are the same but the fuel pumps are differant I just swicthed tanks over.The computer of my 90 was mounted in the dash the one from the 94 is mounted on the fire wall in the engine compartment there was minor fab work to switch everything over but nothing major.If you are looking for just a new motor and staying with the TBI every thing should swap right over.Just use the intake from your 89.The block and head should be the same for both 89 and 91 I think the 97 is also the same but I dont have a TJ I only know for sure about the 90 and94 I have.

[ragincajun]

So I can take the 91 block swap over the intake etc. from the 89, and shoul be good to go.  I will then take the 89 block, and start it on its buildup.

[shotgun]

I am currently doing the same thing with a 90 and 95. so far I haven't found any issues but both motors came complete from the intake to the exhaust and fan to flywheel. So far I haven't ran into any problems other than a broken borla header on the 90.

[TexMontana]

did this myself last year when i blew a hole in the block of my 87 http://www.jeepforum.com/forum/showthread.php?t=142378&highlight=speedometer

just remeber that all the accesories are different like i said in my story

 "So I gather a couple friends and spent a week pulling the engines and getting the 93 2.5 prepared to become an 87 2.5… for what ever reason I thought that would be easier to do instead of replacing the whole wiring harness and computer… well that was fun I’ll tell ya what… lets see… had to swap the engine mount brackets, intake and manifold, power steering pump, alternator, valve cover, water pump, all he pulleys needed to be changed to use the fan belts instead of a serpentine, and various electrical sensors… finally I had a full 87 2.5 engine…."

not a bad proccess really looking back at it... i had so many probs myself doing cause i was in a hurry... not bad at all tho