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post #1 of (permalink) Old 02-06-2004, 11:26 AM
thesandmn
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swapping 258 for 4.0 (242) questions

I'm looking at replacing my 258 (carburated)out of an 85 CJ with a 4.0 bare longblock from an 87 wrangler. The 4.0 is the mpi engine with serpentine belt. Is it possible to swap everything over from the 258 ie. distributor, manifold/carb, exhaust manifold, v-belt pulleys??? thanks
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post #2 of (permalink) Old 02-06-2004, 11:36 AM
 
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Re: swapping 258 for 4.0 (242) questions

How does this 87 have a 4.0L in it? did the PO drop it in? A little background information on the 87 would probably be good, as in any idea on what year the 4.0 is originaly from, if it's got MPI (was that an addon). It just seems rather odd right now? Or am I really off on that?

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post #3 of (permalink) Old 02-06-2004, 09:21 PM
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Re: swapping 258 for 4.0 (242) questions

The jeep I'm working on is an 85 CJ with the original 258 in it. The 258 is worn out and putting out lots of blow-by. I have come across a long block that I'm told is the 4.0l (242) for serpentine belt. The block number has the MX stamp. I looked that up and it is supposed to be a 4.0 for 87-89 Jeep. Not sure if its for Cherokee or CJ though, does it matter? I need to know if I can basically swap long blocks, using the distributor, carb set up and v-belt pulleys from my 258??? thanks
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post #4 of (permalink) Old 02-07-2004, 10:28 PM
 
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Re: swapping 258 for 4.0 (242) questions

I was confused because the 87 wrangler came with a 258. So it would have the 4.2 in it. Then they moved over to the 4.0 in 90-91? not sure.


I would think the block woudln't have a problem bolting in, but i've never done it so am not sure. The distributor on my (88) is on theb left of the heads as you look at it on the front, not sure where it would fit.

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post #5 of (permalink) Old 02-07-2004, 10:30 PM
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Re: swapping 258 for 4.0 (242) questions

Cherokee's are the only Jeeps that had the 4.0 in the late 80's. It used the Renix system, which I believe is TBI, not MPI, but I'm not sure.
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post #6 of (permalink) Old 02-09-2004, 09:12 AM
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Re: swapping 258 for 4.0 (242) questions

It's MPI. I know that being an owner of an '88 Cherokee. The 2.5 had TBI I believe. I bet the easiest thing to let it work proper and really benefit from the swap to the 4.0 is also installing the computer and harness. No idea if the original components (everything driven by the belt) can be used. Depends on how much time you have and what your mecanical abilities are.
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