would it be worth it

what do u guys think of the 258, i think i might replace it with either a 360 amc or a 350 chevy small block would it be worth it i plan on doin alot of offroading in it

 

JMO - keep the 258. It's a great engine.

Depends on what you want from the Jeep. For off-road, in mud bogs or dunes, more power will be helpful. On most trails, the 258 will be plenty - you need the right gearing though.

I think the 258 is plenty for the street, unless you want to do burnouts and impress the high school girls (j/k). It'll travel at highway speeds easily and have enough poop for (sane) passing. You can easily and cheaply hop it up with a 2V intake and carb, HEI ignition and an RV cam.

<edit> If you have the stock T-18 4-speed with the 258, that's a great combination. Customers really liked these Jeeps when they were new. The 258 has a lot of low end torque, and the ratios of the transmission work well in a wide variety of situations - crawling, hill climbing, street driving. You'll have the stock Dana 20 transfer case. If you have the 3.73 axle gears, you might consider upgrading your transfer case to provide more reduction.

 

Go out and trail ride with it with the six, that way when you upgrade to a V-8 you will really appreciate it. Especially with the big tires.

 

258 is a great motor. No real need for a V-8 in a Jeep anyway they don't weigh enough to need the power.

 

I'll 3rd or 4th that. The 258 will do everything you need it to do except burn off the tires. Foe off raod you want low end torque anyway, not high RPM's. Plus it will outlive the V8's. It's darn near indestructible. This is the second Jeep I have had with a 258 & I wouldn't even think about a swap. JMHO

 

X5 Iv'e had several different Jeep models including an 88 Commanche PU. There's a reason the I-6 has been around so long.

 

Like I said, I wouldn't rush to put one in, but more power in a CJ is a great thing. I've seen underpowered jeeps have trouble in long hillclimbs, steep hillclimbs, slippery slopes, sand dunes, and deep mud. Horsepower can get you into trouble, but it can also get you out of trouble. Off-road, high vehicle speed is dangerous, but high wheel speed can be a savior. The 258 is a great dependable engine, but that doesn't mean a stronger V-8 can't be even better.
If you truly plan on off-roading alot, plan on wanting a V-8. In my opinion go with a 5.0 ford or a chev. more performance parts and I'm no expert, but they seem to be more dependable. Very important when you are out in the middle of nowhere.

 

V-8s sound cool, are impressive on the street or out wheeling, but, even a stock 304 will break plenty of drive train parts, go where you probably shouldn't go, get you noticed by the cops in a bad way! I know, blaa, blaa, blaa, but my jeep I purchased in my early 20's with a 360 and I have pretty much broken everything out of v8 stupidity. I still run a v8, but am so tired of upgrading everything that I drive it like a 6! So unless you have extra cash laying around and are pretty responsible, I would do like the others have said, wheel it stock until your abilities exceed your vehicles, then start making your upgrades.
Do I sound like a Dad? Man....

 

Well with a t-18, dana 20 case, dana 44 rear, you would be all right with extra power. Just do not put a locker in a dana 30. The biggest key to not breaking parts is to keep everything properly lubed, and do not let the jeep bounce under power. If your front end catches air, let off the gas pedal.
Again, all that said, I'd still wheel the six for a while.

 

I agree, had a 258 in my YJ. The carb sucked, but we installed EFI and it was a dream. Enough power for 32's on a YJ and better mileage.

 

In my opinon a mildly tweaked 258 has plenty of power for just about everything you need to do.

 

I have plenty of power to spin the tires in my ZJ with the 4.0L when i am in the sand. And that is with a vehical that ways nearly 2K more lbs then a CJ. Really a V-8 is overkill in my book.

 

I would also keep the 258. It's a 4.2 Litre engine, not a 4.0, in case you weren't sure. If you want, you could maybe rebuild it.

I run that engine in my '75 CJ5 with a glass body, which makes the Jeep about 300lbs lighter than stock. I also have 6 into 1 Hedman Headers, a High Intake Clifford Manifold with a Holly 2 BBL Carb. Oh, I also run the Pertronix Electronic Ignition that fits right into where the Points used to be, about $80.00.

With this setup, I have no problem at all burning all the rubber I want off the tires.

Todd.

 

Yep I know. 258 compared to 242 but they are of the same basic design. But I was just showing how a motor that is not as much of a torque motor is effective even in a much heavier vehical.

 

Yup, I agree. But I must say, my brother has an '86 CJ7 with a newly rebuilt 258 4.2, but with none of the mods I have on my engine, and it's much slower than mine. Which I might add, he's ****ed about, ha! He also has a Glass tub.

My engine has not been rebuilt and it has over 100,000 miles on it, and it still kicks ***! Though this summer it started to tick like crazy, so I just added some of that Hydraulic Lifter additive, and the ticking almost stopped completely. But it does need a rebuild. But I'm just going to run it into the ground before I put out the dough. It also burns oil, but who cares?

Todd.