4.0 vs. 4.2

[mingez]

Gimme pros and cons of one vs. the other.

I asked the question on the "87 wranger" thread, but the very funny and entertaining round vs. square, poo poo brown CJ's are rust buckets, and xj's are station wagons cut down extravaganza has over shadowed my questions. (but if you have a chance check that other thread out...very funny)

Thus, I am forced to post another thread.

I did a search and got a whole lotta nothing.

[Junkpile]

Putting the stroker possibility aside, I prefer the 258. You can't kill the bottom end of those things, they're torque monsters. In factory form, I'll take a 4.0 because they have more horsepower. If planning on some mods though, you can get some decent hp out of the 4.2 and enjoy the stronger low rpm torque production available from the longer stroke. The HO head swap(or even a worked factory head), a camshaft that pulls to 5,500 rpm like a factory HO 4.0 will, headers and a good intake will make a 258 flat smoke an HO 4.0 onroad and off. Either one is great though.

[Joopin]

Lets put it this way, I have seen 4.2s converted to EFI, never 4.0 to carb.

[Sully]

258 has got a lot of down low guts. The stock carbs suck. The infamous carter. The fuel injection is much better for steep angles. People say the carters are good for nothing. Which they are. But I get by just fine with mine and I see some angles.

[mingez]

Carters aside, what's the HP difference?

[jeepmaster]

4.0 - 190 horse 235 torque.. dont know bout the 4.2

[mingez]

According to Off Road.com 112 horse? Is that right? :?

[Snitty]

i'm a great fan of the stroker... i JUST MIGHT have a free 4.0 block coming my way... a local garage doesn't want it because it threw a connecting rod... which would be replaced with that of a 258, a complete motor which i'm getting for 40 bucks

[TwistedCopper]

Yes Mingez, that is correct: 112hp vs 180hp (in the TJ, it has 190 in an XJ). Keep in mind the 258 was a victim of the emmissions laws as with many cars in the 80's. That 112 hp rating can easily be increased by letting that baby breathe.

The 4.3 produces 210 lbs of torque while the 4.0L produces 220. In other words the power is there, but speed is not.

[Bounty__Hunter]

My '95 2.5L puts out more HP than the 4.2L

Joopin had a good point.

I-6's are known for thier torque, so get the higher HP and fuel injection of the 4.0L if possible.

[stan]

a 258 will damn near pull the devil out of hell with a good cam some decent headers and by loosing that worthless carter carb. Ive got nothing but good to say about the 4.2 ecept it can be a little cold natured.

[jeepmaster]

ah cold carbs, they're a nightmare in the winters here

[redrooster]

Fool Injection...and don't look back.
P.S. The only thing sweeter than hearing a 4.0 bounce off the rev limiter is hearing me pop the top on an ice cold BEER.

[Snitty]

i've only hit the ref limiter a few times... accidentally... i might start getting on it more though... if i'm getting the frankenstien project coming my way.. then i can afford to abuse

[mingez]

Well, that sucks. I'm a little disappointed.

So, perk me up. What can I do? From drastic to easy. Obvious stuff I know, but fuel injection conversion.. is that a hard swap with that specific config. I remember seeing some threads talking about the difficulty of such a thing... but I don't remember.

And, what about an engine swap? I'm really get beyond my ablilites here, but has anyone done this with that tranny, driveline, etc.

[mingez]

Originally Posted by Bounty__Hunter

My '95 2.5L puts out more HP than the 4.2L

Joopin had a good point.

I-6's are known for thier torque, so get the higher HP and fuel injection of the 4.0L if possible.

Somebody tell me that I shouldn't just settle for a 4 banger. I can find one of them local for crying out loud.

[Junkpile]

The 4.2 was crippled from the factory. It was never offered in any configuration that wasn't heavily choked by emissions equipment. The carb, ignition, intake manifold, exhaust ,cylinder head, and camshaft were all designed with clean emissions and economy in mind at a time when the companies were just learning how to deal with the stricter regulations. ALL engines were low on horsepower through the late 70s and 80s. The baddest boy at the dealerships was the 215 horse Ford Rustang GT, Jeez give the old 258 a break.
Fast forward to now. You can go buy brand new cars with over 400hp that pass all of our even stricter emissions laws.....but how much more torque is that great 4.0 making today than the 4.2 was 25 years ago? 10-15 and at a higher rpm, right? With comparable head flow and cam timing, a 4.2 will eat a 4.0. The 4.0 is easier though.
The reason the stroker is so attractive is becuase you're combining the main characteristics that distinguish these two great engines. You get the bigger bore of the 4.0 with the longer stroke of the 4.2.

[laneiac]

Junkpile is right, the 4.2 isnt a bad engine at all, but if you can go the 4.0 route do it. Less headaches and work in the long run.

[jeepmaster]

screw the 4 cly.. if you're gonna mess w. the engine it doesnt make any sense to go smaller.. i mean LESS power, you know you want MORE, plus MORE gas $$

[TwistedCopper]

The 4.2 will pull up a hill alot stronger than a 2.5L. I know, I've had both.