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Unread 03-11-2011, 04:56 PM   #1
cprettydiddy
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Best Engine to switch to from a 258 inline 6 on an 87 yj

I have a 258 inline 6, but the mechanic says theres a rod knockin around that would cost way to much to replace. He suggested switching to a 350...but not sure what we should do. I have been told that the 258 you can't kill, but keep having all these problems. We took it there just to get the gaskets changed(head, exhaust manifold) but he said he wasn't comfortable taking our money bc of the rod problem, it was going to blow soon anyways. Any suggestions?

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Unread 03-12-2011, 12:05 PM   #2
wendell
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Don't ruin a jeep with a chevy engine. The best engine for an 87 is the 258. To get some more ponies from my 258. I added a offy intake, a holley 470 TA 4 barrel, 4.0 head, rollor rockers, comp cam, header, DUI distributer, MSD and 4:10 gears. It screams, awesome lowend torque and very easy to work on. No computer or sensors to go bad. The holley TA series 4 barrels are made for off road and can take some extreme angles. Chevy engines belong in blazers, the 258 and 4.0 belong in jeeps. It also gives you plenty of room in the engine bay to work and keeps the fuel pump on the engine where it's easy to get to. You can repair it on the trails with a screw driver, pliers, baling wire and a piece of duck tape hee hee!!!
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Unread 03-13-2011, 11:49 AM   #3
cprettydiddy
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Well I kind of figured a 350 wouldnt be the best option. But My 258 has got a rod banging around under the bottom of that 4.2 and would rather replace it then it freeze up on me. Trying to figure out the best option to either replacing the 258 with something bigger and better, but would also like something that would fit pretty easy with the least amount of modificatons.

This is my 1st Wrangler so Im learning along the way.
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Unread 03-16-2011, 12:21 PM   #4
wendell
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You can go bigger, but there is nothing better then a jeep I-6 engine, they pretty much last forever. The 258 hits peak torque at 2000 rpms, thats hard to beat as far as a wheeling motor. There's plenty of performance mods that can be done to the 6, there's even a 5.0 stroker kit if you want bigger and still keep the jeep inline 6.
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Unread 03-16-2011, 12:39 PM   #5
Krochus
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In going to be the voice of dissent

The 258 and 4.0 are good long lasting engines. But the amount of power they put out compared to the amount of fuel they drink is best described as pathetic.

Yes you can stroke em and build one to the nines. But even then they won't even begin to hold a candle to even the most basic v8 swap

If you have some aversion to a non jeep motor (oxymoron if you ask me) then an amc v8 will bolt to your trans and be "jeep" ....or er um depending on what era. A 350 on the other hand kills three birds with one stone. You get rid of your clapped out 258, you gain more power and probably economy and lastly you ditch your POS Peugeot trans

Buick
amc
Dodge
GM
Renault

Are just a few of the engines that have came in the hodgepodge of mismatch parts called jeep

posted via IPhone.
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Unread 03-16-2011, 02:27 PM   #6
tjhawx
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Quote:
Originally Posted by wendell View Post
You can go bigger, but there is nothing better then a jeep I-6 engine, they pretty much last forever. The 258 hits peak torque at 2000 rpms, thats hard to beat as far as a wheeling motor. There's plenty of performance mods that can be done to the 6, there's even a 5.0 stroker kit if you want bigger and still keep the jeep inline 6.
Where can I find info on the 5.0 stroker kit for the inline?
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Unread 03-16-2011, 05:40 PM   #7
Vin
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The Chevy Small block is being used by so people, in so many different vehicles, there's no way you can go wrong with it. Aftermarket parts for Chevy 350s will make a Jeep parts look like a canned goods section of a major supermarket. If you are a purest, then I can see the problem with putting a Chevy in a Jeep, but as far as being a bad choice, far from it.

Let's face it. There is so much room under a YJ hood, I used to climb into the engine bay to change out the spark plugs. A Chevy Big block would still swim in a YJ engine compartment.
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Unread 03-16-2011, 09:41 PM   #8
MAMMOTH
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Not sure how things are in your area but 305's are a dime a dozen compared to 350's
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Unread 03-17-2011, 09:26 AM   #9
AbAngler
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Another option if you don't want to go 8 cylinder is to go fuel injected Chevy 4.3l V6. Its basically a 350 with 2 cylinders cut off. Pretty much everything that applies to a 350 swap, applies to a 4.3l swap. I have been using this motor in my S10 Blazer 4x4 for a few years and it has stood up to alot of abuse and high revs. Has plenty of power, but not so much that you have to worry about breaking things (as often). Also considerably better on gas with parts everywhere.

I'm in the process of doing this swap because the 258 in my 89 had high mileage, and I'm not a fan of carburated motors for offroad applications.
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Unread 07-11-2011, 08:40 PM   #10
cprettydiddy
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I have my hands on a freshly rebuilt 350 that my father-in-law is giving me. It has 0 miles on the rebuild so I can't complain.

My only downfall is that I have no idea where to start to swap out my 258 to the 350.

I know I should get the 700r4 transmission and the 231c transfercase. That's about as far as I got on my research. Any tips/pointers/step-by-step guides out there?
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Unread 07-11-2011, 09:14 PM   #11
jay-h
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Remember switching to a Chevy or other V8 will be a whole LOT more work and expense then putting in a reman 258. Unless you're really bugging for more horsepower, or actually want a major project, it's probably not worth it.
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Unread 07-12-2011, 05:55 AM   #12
cprettydiddy
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I can't really pass up on a free 350 with no miles on it, right?
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Unread 07-12-2011, 06:07 AM   #13
wendell
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Have you lost your mind, there is no better engine than the 258 to switch to. I've had jeeps with 4 cylinder to V-8's and the I-6 is by far the best all around engine in a jeep. The 258 reaches peak torque at around 1,800 rpms, thats like a diesel. To improve on it's topend hp, I installed a holley TA 470 4 barrel, offy intake, comp cam, rollor rockers, ported head, header, DUI distributer, MSD and 4:10 gears. It now has hp to match the torque, runs like a little V-8, but still has the rock crawling grunt of the 6. It's still old school, so there's no sensors or computer to screw with, the fuel pump is still on the engine where it should be. There's still plenty of room in the engine bay to work. Best of all, it's still all jeep. Our 87's are the last of the AMC jeeps, don't mess up a classic. This is the perfect time to build you a nice 258 to rest in your classic yj. A built 258 will run rings around a 4.0 on and off the road. I love 4.0's as well, but were talken 258 here. A stroked 4.0 can be an off road monster as well. The point being, you don't need to dirty up your classic jeep with a chevy V-8 to get performance.
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Unread 07-12-2011, 06:50 AM   #14
cprettydiddy
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I keep hearing the 258 is the cream of the crop. But I see so many jeep wranglers with 350s in them. It almost seems more dominant than the original 258s.....I just want my wrangler on the road and it last a while.
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Unread 07-12-2011, 07:27 AM   #15
stokerdog
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If I had a fresh SBC given to me I would find a NV4500 and get to work. The temptation would be to much to resist. I recently drove a CJ8 that had a swaped in 4.0 from a wrecked XJ the owner had the bought the donor for $400
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