Jeeperinthemud
New member
hey i was thinking about getting a cj7 and i was wondering how the 4.2l engine that it comes with runs, is it crap or does it run as good as the 4.0 ho
4.2 questions
- Thread starter Jeeperinthemud
- Start date
Bounty__Hunter
Super Moderator
RE: 93 wrangler radiator?
Depends a whole lot on what carb it has on it. Tough to get any carbed engine to run as good as the 4.0L HO, but it's still a good engine. It's preferred to ditch the stock Carter carb and go with a Motorcraft carb or FI.
Depends a whole lot on what carb it has on it. Tough to get any carbed engine to run as good as the 4.0L HO, but it's still a good engine. It's preferred to ditch the stock Carter carb and go with a Motorcraft carb or FI.
those motors are great. i would have kept mine if it didnt kick the bucket on me. it was a mystery motor that was swapped in after AAMCO messed up the oil pump in my mint running/performing 4.2 and made it seize 30 miles after picking it up from getting the transmission rebuilt. anyway, when they run good, they work great. when they are crappy, they are real junk. (i guess you can say that about anything... but its night and day with these motors.) Anyway, the carb is the biggest determining factor in whether or not it will run good or not. I got the MC2100 from my old 4.2 for sale with adapter and 10x3 K&N filter/edelbrock air cleaner for sale for $150 shipped if you decide you want it.
jay79cj7
New member
RE: Re: I am a Murderer
I have put 10k or so on my 4.2 in the past couple years and it has run great. I even have the original Carter carb on there. They have a bad reputation, but can work well. (That's why they used them for so many years.) I know mine will eventually succumb to the poor performance that everybody else has, and it sounds like swapping carbs is not too tough if necessary. The 4.2 has a reputation of lasting a long time.
I have put 10k or so on my 4.2 in the past couple years and it has run great. I even have the original Carter carb on there. They have a bad reputation, but can work well. (That's why they used them for so many years.) I know mine will eventually succumb to the poor performance that everybody else has, and it sounds like swapping carbs is not too tough if necessary. The 4.2 has a reputation of lasting a long time.
RE: sick people in the world
The 4.2 and the 4.0 are basically the same engine with a different bore/stroke, for the most part. The longer stroke 258 is a low rpm, stump pulling machine. Maximum torque output happens almost as soon as it starts turning up. The 4.0 is a shorter stroke/ bigger bore combination that runs alot better in the mid-upper range, but reaches peak torque at quite a bit higher rpm, which isn't the best thing for slow speed offroading. The 4.0 feels more sporty, especially with a manual transmission and some good gears.
The neat thing about a 258 is that they are pretty tame in factory form, but it can be turned into a little monster with some simple and common mods. Horsepower can be brought up to and beyond the level of an HO 4.0, while retaining the low-end torque producing qualities of the longer stroke. It takes money to make a 258 run as good as an HO 4.0 on the street. Emissions regulations really played hell with the 258s ability to breath. Head flow sucks, camshaft sucks, intake sucks, exhaust sucks.....do I need to keep going?
The 4.2 and the 4.0 are basically the same engine with a different bore/stroke, for the most part. The longer stroke 258 is a low rpm, stump pulling machine. Maximum torque output happens almost as soon as it starts turning up. The 4.0 is a shorter stroke/ bigger bore combination that runs alot better in the mid-upper range, but reaches peak torque at quite a bit higher rpm, which isn't the best thing for slow speed offroading. The 4.0 feels more sporty, especially with a manual transmission and some good gears.
The neat thing about a 258 is that they are pretty tame in factory form, but it can be turned into a little monster with some simple and common mods. Horsepower can be brought up to and beyond the level of an HO 4.0, while retaining the low-end torque producing qualities of the longer stroke. It takes money to make a 258 run as good as an HO 4.0 on the street. Emissions regulations really played hell with the 258s ability to breath. Head flow sucks, camshaft sucks, intake sucks, exhaust sucks.....do I need to keep going?
Tug-n-pull
New member
RE: Regarding the Site...
Bounty hunter nailed it you get a motorcraft 2150 on there and it is a dynamo! tug
Bounty hunter nailed it you get a motorcraft 2150 on there and it is a dynamo! tug
Are you asking about how a properly running 4.2 compares to an HO 4.0?......or are you wanting to know what carb works best to make a 4.2 run properly? There are many more variables involved in how an engine is going to perform than what carb it has sitting on top of the intake.
LVRockCrawler
New member
i LOVE the 4.2 (bone stock w/the Carter on her) i had a 4.0 in my 91 and the main diff. ive noticed (now it has been a couple years) b/w the 4.0 and my 4.2 is the 4.2 has MUCH more bottom end torque - its a lot tougher to maintain smooth speed in the low end on rough trails - like i saw someone post b/4 - the 4.2 has enuff torque to "pull the devil out of hell!" - i dont really miss the FI on the 4.0 except for when i'm getting into weird angles and worried about the carb starving or flooding....thinking about the TBI swap i saw on an old episode of "trucks" where Stacy did it on a CJ8....
GaryMB
New member
RE: Re: RE: New engine and transmission for my 84 CJ7
i have an '84 cj7 w/258 and carter carb. I love the bottom end torque; if you step on the gas the jeep leaps forward (and then with it's amazing 113hp accelerates a little). The carter carbs tend to become worse as they get older (rough idle, harder starts, sometimes just dies, etc.), and a a new carb will have the best results. MC2100's are a good and cheap carb swap. To gain about 40hp, put a 4.0L head on the 4.2L (you will need to plug up some water passages, though). If you really want the best of both worlds, put the 258 crank and piston rods in the 4.0L, assuming your transmission is up to it. BTW, i saw that trucks episode too...TBI would be nice for hills and those off-camber situations.
i have an '84 cj7 w/258 and carter carb. I love the bottom end torque; if you step on the gas the jeep leaps forward (and then with it's amazing 113hp accelerates a little). The carter carbs tend to become worse as they get older (rough idle, harder starts, sometimes just dies, etc.), and a a new carb will have the best results. MC2100's are a good and cheap carb swap. To gain about 40hp, put a 4.0L head on the 4.2L (you will need to plug up some water passages, though). If you really want the best of both worlds, put the 258 crank and piston rods in the 4.0L, assuming your transmission is up to it. BTW, i saw that trucks episode too...TBI would be nice for hills and those off-camber situations.
