258 vs 4 banger

258 vs 4 banger
Kirbot

Kirbot

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South Jersey
Vehicle(s)
Cj7, 258 I-6, T18, D300, D30, Amc 20
Pretty soon I'll be picking up a yj, I'm going to use the body and maybe some other parts from it on my Cj.

What I'm wondering is, should I rebuild the carbureted 1987 AMC 258 i6 / 4.2l AMC 258 i6 / 4.2l liter thats in the Cj now, or should I use the fuel injected 4 cylinder thats in the Yj.

The AMC 258 i6 / 4.2l needs alot of work, it burns an awful lot of oil, smokes like crazy, the bearings make an awful racket...

I don't know about the 4 yet, but I know it runs, just not sure how well yet.

Thoughts and opinions?
Any clue on how much I might have to spend on the AMC 258 i6 / 4.2l , like, under $1000?


Oh yeah, thats a Weber carburetor in there.
 
Hmm, not a bad idea.

My dad was saying it could be rather complicated switching to a fuel injected engine.

Just how tough is it?
 
Mounts, motor,Transmission ,Transfer Case , wiring, sensors, exhaust, misc.
All you already have on the donor vehicle, then it's just time
and motivation. More or less.
Or you can sell all the good parts and buy a new long block
or even a stroker motor.
http://www.quadratec.com/products/51107_50X_PG.htm

Info:
http://www.jpmagazine.com/techarticles/engine/154_0508_golen_4_6l_stroker_engine/index.html
http://www.jpmagazine.com/techarticles/engine/154_0509_golen_4_6l_stroker_engine_2/index.html
http://www.jpmagazine.com/techarticles/drivetrain/154_0512_golen_4_6l_stroker_engine_3/index.html
 
Last edited:
BrockGrimes said:
Mounts, motor,Transmission ,Transfer Case , wiring, sensors, exhaust, misc.
All you already have on the donor vehicle, then it's just time
and motivation. More or less.
Or you can sell all the good parts and buy a new long block
or even a stroker motor.
Golen Engine Service WRANGLER - GOLEN 4.6L / 260hp Long Block Drop-in Stroker Engine - Quadratec

Info:
Golen 4.6L Stroker Engine Part 1 - Tech Articles - Jp Magazine
4.6L Golen Stroker Jeep Engine Upgrade - Tech Articles - Jp Magazine
Golen 4.6L Stroker Engine Part 3 - Tech Articles - Jp Magazine
Click to expand...

Ya know, I hadn't even considered getting a different engine, I just assumed they would be a lot more expensive than they are.
I just found this website and I'm starting to think it might be the best way to go.
High Performance Jeep AMC Engines
$1114.00
for a rebuilt AMC 258 i6 / 4.2l
That doesn't sound to bad to me.

I think I might just do that.
It's probably a little more expensive than rebuilding this one, but I think for my lack of experience it's probably worth it.

Opinions?
 
Consider the 4.0 motor?
A good 4.0 runs like a scalded dog.

Put me down for a no vote on the 4 cyl. by the way.
 
Sasquach said:
Consider the 4.0 motor?
A good 4.0 runs like a scalded dog.

Put me down for a no vote on the 4 cyl. by the way.
Click to expand...

I thought about it briefly, would it be much harder to switch to that?
It's fuel injected right?

I realize I'm asking a lot of what are probably pretty basic questions, I'm new to working on cars.
I'm a very mechanical person, I've worked on/used/restored/ metal lathes, drill presses, woodworking tools.... But I just haven't had much experience working on cars yet.
 
It would be more complicated than rebuilding what you have for sure, There are a lot of write ups on the switch and if you have good junk yard access and the time it might be something to look at. The 4.0 motor is fuel injected and puts out around 190HP compared to the AMC 258 i6 / 4.2l at 110HP +-
You would need a donor cherokee or wrangler for the complete motor and wire harness.
 
you'll regret puttin that pos 4 banger in your jeep. that wore out old AMC 258 i6 / 4.2l has double the power that 4 cyl could ever dream of havin. you can rebuild the AMC 258 i6 / 4.2l for around $1,000 maybe less if you gotta buddy at a machine shop. goin with a 4.0 aint a bad idea at all either, although would be a little more trouble than rebuilding what you have
 
Hmm, I think the 4 is out, I want to run 33" tires and use it as a daily driver, the 130 hp, 120 torque(or whatever) it is, sounds like it would be almost dangerously slow. I want to atleast be able to get out of my own way.

Now it's kind of between buying the rebuilt engine, or trying to do a cheap-<-BAD WORD-> rebuild my self. Like, hone it myself, new rings, just do as little as possible to get it running half decent and save up to eventually convert to a 360 or a 350, or something along those lines.
I don't see much point to doing a full rebuild myself, it wouldn't cost much(if any) more just getting one already done. And until I have more experience around engines, it's probably the better choice.
 
If you want the V-8 now's the time to do it.
Sell the parts you don't need pick up a good V-8
and run it.
 
For the record output the final year for the 2.5L was 121 hp at 5400 rpm and 145 lb·ft of torque at 3250 rpm using sequential multiple-port fuel injection. For comparison, the AMC 258 i6 / 4.2l I6 provided 112 hp at 3200 RPM and 210 lb·ft of torque at 2000 rpm in its final year with the computer-controlled carburetor.

The 2.5 L inline-4 was a shortened version of the AMC 258 i6 / 4.2l 6-cylinder engine bored to 3.875 in (98.4 mm) and de-stroked to 3.1875 in (80.96 mm). The block is basically the same as the legacy AMC 258 i6 / 4.2l cu in (AMC 258 i6 / 4.2l L) engine with a larger bore and the two center cylinders removed. The head featured a new combustion chamber and port design that was later used on the 4.0 L — the 2.5 L I-4 head was stretched by two cylinders in the center.

It's not a bad little motor I owned a '94 YJ with a 4 and in 1st 4L it would crawl with no touch of the gas, that thing was a little mountain goat.

But the OP said he'd like to do a V-8 swap so like suggested I'd sell the :dung: I don't need and do the v-8 swap. However I like the AMC 258 i6 / 4.2l and would be more inclined to rebuild it but make it a 4.6L. You can buy all the needed parts in a kit all you need is to have the machine work done.
 
Well, thats a possibility, of course it means upgrading the Transmission to.

I'll look in to it some more, but I assume it will be more than I can spend.
 
I think I'll probably just get the rebuilt AMC 258 i6 / 4.2l .
I don't wan't to go in over my head with trying to swap to a 360, and having a like new engine in it will be nice.
I wan't it to be atleast fairly reliable.
 
take the crank, head, block, and rods to the machine shop with you buy a master engine kit and it will be a new engine

this is what i used
71-90 Jeep 4.2 258 Engine Master Rebuild Kit: eBay Motors (item 370407882447 end time Jul-20-10 12:04:23 PDT)
its an engine tech kit they buy name brand parts wholesale and put em in their packaging, i got clevite 77 bearings, silvolite pistons, sealed power rings, melling oil pump and cam, etc. its a hell of a deal.
depending on the machine shop, all of the machine work will cost between $350 and $600. i had the head and block magnafluxed, hot tanked, bored .30 over, head and block decked, valve job done, crank polished, new cam bearings installed, rods hot tanked, and the new pistons pressed on all for a grand total of $375. this will give you an idea of what it'll cost to rebuild a AMC 258 i6 / 4.2l
 
A lot of good opinion in this thread about everything, except never using a 4 banger, I have owned 2 4 poppers in jeeps, a 65 with 80 hp and a 04 with 145 hp, both were very do able engines for a Jeep, however I think that most of the 4 piston engines Jeep has used are a little pathetic for the street.
My advice is that if you are going through the entire process of a frame up, YJ tub etc then go and look for a fuel injected 4.0 and use it. The engine may not get more gas mileage than a v8 but it is one of the greatest wheeling engines ever developed, it holds 80 percent of the torque at idle so it delivers the performance where a off road machine needs it, Any way you go it looks like the grand you have for the engine is just a start anyway, a rebuild will use that up quick and ask for more unless you skip this and that.
Good luck with whatever you do, and hope to see pics of the build posted
 
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