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post #1 of (permalink) Old 12-28-2001, 11:14 PM Thread Starter
 
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What are the pitfalls of the 258 motor (newbie ?)

Came over from the Cherokee board because I could use your guy's expertise on this. What are the pitfalls and badpoints of the 258 inline six? From looking at catalogs such as PAW and other sources it seems that performance mods are plenty and much cheaper than it's newer cousin the 242 fuel injected motor. I would think a person could easily build this motor up into a good torquer a lot cheaper than the 4.0 but I'd like to hear about possible design flaws, what are the best mods...

Thanks in advance!

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post #2 of (permalink) Old 12-28-2001, 11:46 PM
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Re: What are the pitfalls of the 258 motor (newbie ?)

Welcome! The 258 is a beast strong engine. The only downfalls that I have heard of or experienced are from the dreaded Carter BBD carb and the leaky plastic valve cover. As far as best mods go, my first would be fuel injection. Howell and Holley both make kits for the 258. Second would probably be a good bottom end torque camshaft and an aluminum valve cover to replace the leaky stocker. I am not a big fan of headers on anything that is street driven, and you just dont need 'em on a motor that makes it's power below 3000 rpm, but lots of guys here have installed the Borla header with good results.
The best thing to do is keep it simple and this motor will take you down many trails as well as a built V8! Hope this steers you in the right direction.[img]/wwwthreads_images/icons/smile.gif[/img]


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post #3 of (permalink) Old 12-29-2001, 12:10 AM
 
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Re: What are the pitfalls of the 258 motor (newbie ?)

Yes, the 4.2 is made for stong torque. It is not knows for revs though. The Carter carb is the downfall. but that can be fixed with about any other carb.

Headed for Gunnison, soon....

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post #4 of (permalink) Old 12-29-2001, 01:13 AM
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Re: What are the pitfalls of the 258 motor (newbie ?)

Another weakness of the 258 is the head. It's a lot more restrictive than a 4.0 head. So a popular thing to do is to swap a 4.0 head onto the 258. Also, don't expect to be winding the engine up into high revs, from what I've heard they don't like that. Atleast not stock ones. I've heard the valves start to float(correct term?) I agree with the crappy, leaky valve cover. Slap a nice aluminum one on there. I also agree the carter carb is a POS! You could either slap a weber on there, which I've hear helps alot, or go with FI, which was mention earlier.

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post #5 of (permalink) Old 12-29-2001, 02:02 AM
 
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Re: What are the pitfalls of the 258 motor (newbie ?)

4.2, a great engine. Downfalls are the carburetor. Contrary to what is being said on here, I dont like the aluminum valve covers as they tend to warp more from my own personal expierience. Aslo, on the YJ they require drilling and tapping holes in the engine, which doesnt work for me.

True, these 4.2's dont like high revs, but who needs to go faster then 45? [img]/wwwthreads_images/icons/smile.gif[/img]

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post #6 of (permalink) Old 12-29-2001, 02:50 PM
 
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Re: What are the pitfalls of the 258 motor (newbie ?)

Anyone else, i'm curious about the general concensus as well. i would think 4.0: better for street, 4.2: better for off-road. Do people have problems with the 4.0 head on the 4.2? Shorter life, anything? What issues are the known to traditionally kill the stock 258?

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post #7 of (permalink) Old 12-29-2001, 03:28 PM
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Re: What are the pitfalls of the 258 motor (newbie ?)

The 4.0 EFI motor is a great off road engine as well. IMHO if you are going through the mod's to install a 4.0 head on a 4.2 (258) why not just put a 4.0 in the Jeep? I have both, 258 in my CJ and 4.0 HO in my '91 Cherokee, and I tend to like the 4.0 alot better. This may just revert back to the crappy Carter carb on the 258 though. I've seen both engines go well past 200,000 miles and they both build good torque.
Ben, not to critisize, but the aluminum valve covers warp? I'm fairly new to Jeeps but I've had cast aluminum valve covers on all kinds of motors, including Big Block MoPars with stock exhaust manifolds (anyone who knows these manifolds knows what I'm talkin' about[img]/wwwthreads_images/icons/mad.gif[/img]) and aluminum covers are the only thing I could get to seal most of the time. I'm not sure about the drilling issue with installing these covers on 258's, but my '83 had the holes I needed. They just had to have a bottoming tap run through them to instal the 4WD Hardware cover.


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post #8 of (permalink) Old 12-29-2001, 07:53 PM
 
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Re: What are the pitfalls of the 258 motor (newbie ?)

My Wrangler has the 258, and its a decent engine. I replaced the sh*tbox Carter BBD with a Weber 38 and that helped a ton. I don't know why they say these are low-revving engines only, as mine would wind up to 5k pretty easily [img]/wwwthreads_images/icons/crazy.gif[/img]

I think I like the 4.0 non-HO in my Comanche better though, and would keep it rather than swapping it out. A 4.0 to 4.2 conversion seems more like a step sideways rather than a step up. If your looking for a stock engine with more power, look into AMC V-8s (304, 360, 401, etc...). They'll bolt right up where that 4.0 was without too much difficulty [img]/wwwthreads_images/icons/wink.gif[/img]

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post #9 of (permalink) Old 12-29-2001, 10:23 PM
 
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Re: What are the pitfalls of the 258 motor (newbie ?)

They seem to also develope blowby problems,mine did and others on this board have .Although you can never be sure how a previous owner may have beat it up or the maintenence record.So if you are looking to buy one look in that aircleaner first for oil.Although there are many bandaids for this problem there is only one cure.

Ray
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why does everyone ask if I am gonna paint it ?
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