# 1989 4.2 Yj



## PLOWMAN45 (Jul 2, 2003)

anyone know the horsepower/tourgue ?


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## Danscapes (Jan 12, 2008)

Not enough, junk the motor and swap it out with a 350


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## PLOWMAN45 (Jul 2, 2003)

i just want the old specs


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## theplowmeister (Nov 14, 2006)

Wow danscapes you got a Little to much testosterone?

That Cherokee engine which is the same motor had 177 HP and 225 Ft/Lb torque.


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## tvpierce (Aug 7, 2003)

Here you go: (I copied the text below from this site: http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=277060 )

_The 258 used in '87-'90 Wrangler YJs uses a computer controlled Carter BBD. 
It is very simlar to the 258 used in '82-'86 CJs, but performance suffers 
due to emmission controls.

AMC 258 I6
Bore x Stroke	3.75" x 3.90"
Displacement	258 (4.2L)
Compression Ratio	9.2:1
Horsepower (net)	[email protected]
Torque (net)	[email protected]
Main Bearings	7
Valve Configuration	OHV
Fuel 2bbl Carter BBD_

And no, that's not a typo. 112hp is the spec for that year 258. (Mine is an '85 so it's just slightly better but not much: [email protected], 210ft/[email protected]) But the real strength of these engines is the torque. Not so much the amount of it -- 210 is much lower than what a V8 puts out -- but the fact that it comes on at such a low rpm. My 258 puts out 210 ft/lbs at 1800 rpm. At 1600rpm, it's at about 85% of that. At 1400rpm, it's at about 75% of that. That's 157 f/lbs at 1400 rpm! That's just above a fast idle! I looked for hp/torque specs for a Chevy 350, and came up with this Camero page:
http://www.camarosource.ca/main_new_site.php?url=new_site/faqs/2nd_gen/answers.htm

Scroll down to the hp/torque chart. Then look at the 1975 and later specs. A 350 V8 putting out 155 [email protected], and 245ft/[email protected] I'd have to see the dyno chart, but I'd bet my left nut that at 1400 rpm, it's quite a bit below my 258's 157ft/lbs.

For people who don't understand the relationship between work & hp/torque, the V8 seems like a better powerplant, because it has higher gross numbers. But experts will tell you that inline 6 engines (by Jeep, Ford, Chevy, Dodge, etc.) are widely consider the ideal engine for work applications, like plowing.

BTW: the 177hp, 225 ft/lbs that Plowmeister quoted sounds like the spec for a 4.0 ltr. -- much higher hp, slightly higher torque, but it comes on at a much higher rpm.

jp


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## PLOWMAN45 (Jul 2, 2003)

i always new it low on horsepower but high on the torque


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## theplowmeister (Nov 14, 2006)

Nope what I quoted is for a carberaded 4.2 (I got the numbers of the web) and 115 Hp sounds very low. the 4.0 had 198 HP and the torque was around 180 - 205 I can't remember I've had both engines in my jeeps.


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## PLOWMAN45 (Jul 2, 2003)

the only way to make that engine right is a new manifold and 4 barrel holley


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## tvpierce (Aug 7, 2003)

theplowmeister;509370 said:


> Nope what I quoted is for a carberaded 4.2 (I got the numbers of the web) and 115 Hp sounds very low. the 4.0 had 198 HP and the torque was around 180 - 205 I can't remember I've had both engines in my jeeps.


I'm not trying to be difficult,  but the #s I quoted were also from the web -- for what that's worth. I certainly could be wrong, but your hp #s sound *way* high for a 258 -- where did you find them?

Not that this "JeepOffRoad.com" web site is the be-all, end-all... but according to them, you're very close to the specs of a 4.0:

http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=261542

Amazing stat when you look at it: the 210 ft/lbs of torque on the 4.0 doesn't come on until 4000 rpm. That's aweful for in L6.

jp


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## theplowmeister (Nov 14, 2006)

WOW we sertinly got difrent answers. tomarow I'l look in my owners manual but I know the torque is way lower than 4000 rpm It's runing out of pep by then. Off road its a real low end tugboat. and pushing snow its got lots of low end ba**s I have a SHO with high end torque and the Jeep aint it.


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## theplowmeister (Nov 14, 2006)

WTF My owners manual has NO info on HP or Torque...... NON:yow!::yow!::crying:


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## tvpierce (Aug 7, 2003)

theplowmeister;510090 said:


> WTF My owners manual has NO info on HP or Torque......


Frankly, I'm not surprised.

I bet there's a whole chapter though on using the stereo and optional DVD player. And yet another on using the cup holders.

A sign of our times.

jp


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## watchamakalit (Jan 11, 2004)

tvpierce;510141 said:


> Frankly, I'm not surprised.
> 
> I bet there's a whole chapter though on using the stereo and optional DVD player. And yet another on using the cup holders.
> 
> ...


Spoken like a true CJ owner.:salute:


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## tvpierce (Aug 7, 2003)

This write-up in Wikipedia gives a good explanation of the advantages of the inline-6 design.

http://en.wikipedia.org/wiki/Straight-6

Here's an excerpt from it that will make you feel good about your 258:

Another noteworthy straight-6 engine family was introduced by American Motors (AMC) in 1964. These engines were used in a variety of AMC passenger and Jeep utility vehicles. They were also assembled and marketed internationally. Some markets (such as Mexico - by VAM) built their own specialized versions. This engine is considered to be one of the best ever made and it received modifications and upgrades as engine control technology improved.[13] It is noteworthy that this "modern era" I-6 was produced continuously for 42 years (even after Chrysler's buyout of AMC in 1987) all the way through 2006. It featured a durable design with a cast iron block and cylinder head, hydraulic lifters (with non-adjustable rockers), and seven main bearings. Since the cars were designed to take the weight of an optional V8, AMC found the easiest way to solve it was by making the straight-6s much stronger and heavier than they needed to be. As a result, the engine blocks were so sturdy that they were used in race cars in the Indianapolis 500. In the 1978 race, an AMC 199 cu in (3.3 L) engine produced 875 horsepower (652 kW) at 8,500 RPM with 80-inches of manifold pressure.[14]

A significant step was taken by Kaiser Jeep with the 1963 Tornado straight-6, the first U.S. designed mass-produced overhead cam (OHC) automobile engine. However, it was complex (by 1960s standards) for civilian vehicles in the U.S., but continued to be installed in military Jeeps and was also produced through 1982 by IKA in Argentina.

(Here's the link to the whole inline-6 entry http://en.wikipedia.org/wiki/Straight-6 )


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## tvpierce (Aug 7, 2003)

theplowmeister;509797 said:


> I have a SHO with high end torque and the Jeep aint it.


Hey PM,

First off, I have total Jeep envy after looking at your latest pix of your new Boss V in another thread.

Secondly, how do you like that V6 in the SHO? I know it was disigned with/by Yamaha, and is supposed to be a real screamer -- and quite smooth. I always thought it was a shame Ford didn't use it in anything else... especially a RWD, like maybe a special edition Mustang.

How do you think it stacks up to a small V8?

jp


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