304 vs. 258? Which way to go???

[Texxas]

Well here is the situation...I have the option to put in a AMC 258 i6 / 4.2l six cylinder or a AMC 304 into my 1983 CJ7 project. As of now I am thinking I will leave the stock Dana 30 front axle and Dana 20 rear (with new one piece axle shafts). I am not going to be doing any heavy off roading or major abuse...light stuff around the ranch. Jeep will be a daily driver...we live in the mountains (hills to Arkansansans...mountains to a Texan

Would like to hear pros and cons. Whichever engine I pick will be tuned and professionally installed.

Thoughts???

Thanks!

Texx

 

[hole]

For a DD I cant help but give the nudge to the 6 cyl personally. Mine is FI and is one heck of a runner. Also the 15-18 mpg is a plus!

 

[ken98k]

I like the AMC 258 i6 / 4.2l in my CJ5 . Seem to be plenty of power, (for me) lots more power than the 2.5 L in my YJ.
Did you mean AMC20 rear? I think the Dana 20 is a Transfer Case .

 

[CJim7]

The AMC 258 i6 / 4.2l is a great engine. Great lowend torque, 7 main bearings, simple to work on, and reliable.

The downside is the 4500rpm engine redline. Because of the design of the motor, you simply run out of engine when you need it. That's where having the V8 is nice.

Power-wise, you really aren't gaining much with a AMC 304 over a AMC 258 i6 / 4.2l , and mileage will be very close to the same if not a bit lower with the V8 depending on how you aspirate it.

 

[gert]

Hmmmm the AMC 304 is a small V8 and you live in the hills the 6cly has gobs of torque. I would say it will boil down to what do you want? how much are you willing to spend to get it...if you do the V8 I highly reccomend a new oil pump which is $300 Does either motor need a rebuild? are you willing to spend the money for it? I personally like the V8 as I swapped to a 360 and I have enjoyed the heck out of it

 

[CJim7]

...if you do the V8 I highly reccomend a new oil pump which is $300 :

Just to clarify that....
The oil pump is integrated into the timing cover which is the expensive part. When shaft clearance is compromised, you lose oil pressure causing you to have to buy an entire timing cover to fix the problem.

Rebuilding the pump itself is dirt-cheap.

 

[jeepy]

This is a no-brainer. If you just want reliable, get the AMC 258 i6 / 4.2l , it is more reliable.
If you want anything more than that AT ALL, get the AMC 304 .

Yep, the AMC 304 should probably have the oil pump/housing rebuilt. But put a 4 barrel carb and and some degree of free exhaust on it and that AMC 304 will blow the doors off any AMC 258 i6 / 4.2l . Power is your friend on the hills, and also when you crossed that ditch just a little too slow on your farm.

I see that you already have one 6 cylinder Jeep. Why have two?

If you are concerned about fuel mileage.....Sell it!

 

[Cheepjeep85]

AMC 258 i6 / 4.2l will run forever, you probably won't ever have to do anything else to it, good torque, decent mpg. a stock AMC 304 doesn't make that much more power than a stock AMC 258 i6 / 4.2l . the AMC 258 i6 / 4.2l will also be cheaper to build. sure it don't sound like a v8, but i believe it is the better motor of the two, if you want a "real upgrade" then go small block chevy.

 

[Old Dog]

I vote for the V8.:madjeep:

 

[CJim7]

if you want a "real upgrade" then go small block chevy.

Nu-huh....401 or even 360 :booze:

 

[gert]

Nu-huh....401 or even 360 :booze:

LOL I LOVE MY 360

 

[Cheepjeep85]

Nu-huh....401 or even 360 :booze:

yeah or that, but i am a chevy guy on top of a jeep fan. i like a mix

 

[Texxas]

I like the AMC 258 i6 / 4.2l in my CJ5 . Seem to be plenty of power, (for me) lots more power than the 2.5 L in my YJ.
Did you mean AMC20 rear? I think the Dana 20 is a Transfer Case .

Yes AMC20 Rear sorry about that.

Texx

 

[Mattduran]

Really if your using this as a farm jeep not as an offroader, and keeping it basically stock I would go with the AMC 258 i6 / 4.2l . There a solid motor and all you would need for your purposes it sounds. They are easy to find parts and better on gas. I luv my beefed up AMC 304 but pretty big into off roading. Good luck!

 

[CJim7]

yeah or that, but i am a chevy guy on top of a jeep fan. i like a mix

psst...dont tell any of my Jeep friends, but if my 401 ever goes south, Im dropping in a 454

 

[Texxas]

psst...dont tell any of my Jeep friends, but if my 401 ever goes south, Im dropping in a 454

:drool: Now that is awesome lol!!!

Texx

 

[CJ]

psst...dont tell any of my Jeep friends, but if my 401 ever goes south, Im dropping in a 454

 

[fcb212003]

I had the same question and did some research. Everything pointed to staying with the AMC 258 i6 / 4.2l .

 

[BigAl77cj5]

My CJ5 has a AMC 304 that has been gone through by one of the previous owners. Seems to have lots of power. I love it. My dad wanted a 360 for his CJ7 said he wouldn't put a AMC 304 in it. After he drove my five a few times he was trying to con me into trading him for is AMC 258 i6 / 4.2l . I was like yeah right I'll keep my v8.

 

[Cheepjeep85]

psst...dont tell any of my Jeep friends, but if my 401 ever goes south, Im dropping in a 454

i knew you were an ok kinda guy.