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post #1 of (permalink) Old 09-06-2000, 12:25 PM
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engine swap for \'88 YJ?

So, my 258 I6 decided to blow it's rear main seal this weekend. It is "hissing" really good @60-70 mph in 4th when you mash the gas, but not under no-load conditions. Anyway, I am thinking the rings are no longer sealing well (111K miles) and am wondering what my engine rebuild/replacement options are. I thought I have heard of ppl dropping 318's into YJ's, I would like the extra power as my Jeep struggles to hold 75mph in 4th, with the gas flat on the floor, nevermind trying to stay above 65 in 5th! So, how much is a rebuilt 258 compared to buying a good used 318 or 360 and the parts I would need to drop it in? Would I need different motor mounts? I guess an exhaust system would need to be fabricated, and I could just run a straight 4-barrel w/o the crappy computer controlled idle and crap like mine has now. I have the Pugeot 5-speed on mine, will the V-8's bolt right up to the bell housing/splines?

Any help is appreciated,


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post #2 of (permalink) Old 09-06-2000, 01:17 PM
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Re: engine swap for \'88 YJ?

I know what you mean about lack of power on the 258. I have a wrangler with the same problem. There are a few options,
1- V8 swap, 2-EFI kit, 3-rebuilt 258 with headers, new carb, etc. In my CJ I chose to swap in a chevy V8. It is actually cheaper
to get a rebuilt (stock) 350 than it is to get a rebuilt 258. Of course there are extra costs involved to get it in the Jeep. The main
downside is that it won't be emmisions legal unless you get an engine newer than the Jeep ($$$). So I guess if it needs to be
emmisions legal it will cost more. The 350 I have is what is reffered to as "off road only" it is so simple, none of the extra wires
and hoses that are so common on the 258. Oh and about your tranny, I would get rid of it in favor of something stronger. Mine has
112k on it and is starting to show its age by grinding/other shifting problems, synthetic fluid really helps though. Good luck

post #3 of (permalink) Old 09-06-2000, 02:06 PM
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Re: engine swap for \'88 YJ?

If you decide to go with a V8 then go to www.advanceadaptors.com. They will have almost everything you need. Ditch your tranny at the same time, the BA/10 or Pugot tranny is the worst ever in a jeep. You could find a wrecked chevy or GMC truck newer than '88 with less than 75,000 mi., it would be a good swap. Get the engine, computer, wiring harness, bellhousing, and tranny(you can do either an auto or manual, depending on what you find, most at this point go with the 700R4 auto, you can get the parts to switch from a manual to auto for fairly cheap). Get the motor mounts, tranny tail housing adaptor(to go to your x-fer case), and x-fer case input gear from AA. Before you start ordering parts look under the jeep and verify the x-fer case. You could have either a NP231 or NP207. This will be stamped on a tag on the rear of the x-fer case. If the NP207 is there, I would suggest a NP231D from a Dodge Dakota be located for a swap as well(this has a larger chain for the V8 power). The NP207 is a ligher duty than a NP231, it might stand up to V8, or not. In V8 jeep the NP231J is considered marginal, this is not to say that many people don't get by just fine with a NP231J. Hope I could help. Get the buyers guide from Advance Adaptors, it will help alot more than I ever could.


[]llll[] '90 YJ, NV4500, XD9000i, 35" MT/R, Snorkle, etc. etc. etc.
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post #4 of (permalink) Old 09-06-2000, 03:23 PM
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Re: engine swap for \'88 YJ?

You should ask yourself if you really want to waste time on it...I did and I'm still married (he,he,he...doh!). After about $6K down the road I think I could be ready to start my '89 YJ this weekend. I did wanted it to be street legal since I live in Chicago. If you can get away with emmisions you can get it done for a lot cheaper. Just like the other guys said, when you swap the engine it's not only the engine, it's everything else that is too weak as well...BUT, if you like your jeep than YEAH!!! definitely V8 swap. After a few month of struggle with mine I still think it's worth it Check out my pix nightmare

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post #5 of (permalink) Old 09-07-2000, 09:10 PM
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Re: engine swap for \'88 YJ?

Nightmare? That looks like fun. I could spend hours just tweeking away like that. Looks like you have a good spot to work in too.

Tread lightly and stop to smell the roses - Traveler
post #6 of (permalink) Old 09-07-2000, 09:34 PM
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Re: engine swap for \'88 YJ?

First thing you should consider is if you live in an area where you will have emissions testing. If that is not a problem i would consider a 4.0 and tranny out of a newer Jeep out of a wrecking yard.It would proabably be the easiest swap and 4.0s do have a reputation for lasting.

post #7 of (permalink) Old 09-07-2000, 10:41 PM
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Re: engine swap for \'88 YJ?

if emissions are of no concern.. then the cheapest upgrade is to find yourself a old 1/2 or 3/4 ton truck.. all rusted to heck and back.. you just want it running.. then.. take everything out of it.. engine, tranny, transfer case, and axles.. put them in your jeep.. get some driveshafts made.. and run an exhaust..
going with a v8.. that tranny will NOT hold up.. then if you want to keep that crappy transfer case.. you will need some bucks for an adapter.. or another transfer case.. and with drivers side front diff.. well your are limited to transfer cases.. so you would be better off swapping out everything.. upgrade.. go bigger.. you wont regret it.. of course.. if thats too much work.. i would just get a long block 258 for like 800 bucks or so.. and put that in.. your choice.. but think in the long run..

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post #8 of (permalink) Old 09-10-2000, 02:34 PM
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Re: engine swap for \'88 YJ?

The "hissing", lack of power and leaking oil seals (due to the increased backpressure in the crankcase) that you are experiencing is probably due to a plugged cat-con, have an exhaust shop check your backpressure! New cat should cost less than $200 installed! A reman 258 should cost around $1200, for a quality job with a good warranty, (no less than $700 if they skimp on the parts). Mopar remans cost around $2000.

As far as a Mopar Magnum V8 swap goes, a switch to a 3 speed 999 or 727 automatic would be your best bet, unless you can find a NV 3500 or NV4500 5speed equipt 4X4 Dodge. Using a '94-'95 YJ slave will connect the clutch pedal to the trans easily, and the t-case from the Dodge would work well if you installed a slip yoke eliminator, (or rear shaft parts out of your 231 t-case). No aftermarket adapters would be needed.

The Magnum V8 would require a larger radiator with inlet and outlet on the opposite side, and fabrication of engine mounts, (as ready made ones aren't available). Dodge truck/Van exhaust manifolds will fit fine. '95+ Ram truck mounts would be the best factory mounts and are the easiest to make fit. The engine package is approximately 3 inches shorter than the 258.

If you wanted to keep the EFI, you would have to modify the factory harness, add a 4.0l, in-tank fuel pump (or add an external pump), mount the controller, etc.

There is a manifold available to mount a 4 barrel carb on the Magnum engines, and the earlier smallblock Mopar ignition parts will fit fine.(if you don't need to smog it).

The cost could be kept under control, if you are capable of doing most of the work yourself. The engine, trans and t-case should cost around $3000 at a wrecking yard, most will guaranty them and may even take in your old parts as partial trade. Try to find a yard that would be willing to work with you, as you will probably need to go back for a part or two.

Hope this helps, good luck!

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