8 cyl. versus 6 cyl.

[Micha]

Newbie here, so go easy on me please. I am in the market for a CJ7 , owned a CJ5 over 30 years ago. Looked at one the other day and took her for a test drive. I must say that 6 cyl. did not impress me much. So now I found one with a 401 installed. Can't wait to check it out.
How much of a premium is the 8 cyl. over a 6 cyl. ?
Pros and Cons?
Thank you for your input...

 

[mriplaybass]

A healthy AMC 258 i6 / 4.2l is a great engine. Easy to work on, and dependable with plenty of power.

A 401 in a Jeep is probably the dream of many CJ owners. The reality of it is, unless the rest of the Jeep is set up to handle the extra power, (Transmission , Transfer Case , axles, etc.) and you just can't resist getting on the skinny pedal, you're probably going to break things.

 

[TnCJ]

I agree with MrBass.
Jeep CJ's are not built for speed. They aren't geared to go fast but to have lots of torque. The AMC 258 i6 / 4.2l [AMC 258 i6 / 4.2l ] engine is a proven performer and IMO the perfect engine for most all round driving situations.
Perhaps the CJ you test drove had a tired engine and needed some work?
You can pretty much put any engine under the hood with the right adaptors etc. Some engines are an easier swap, i.e. the AMC 304 , 360, 390 and even the 401 [I think].

 

[Lumpy Grits]

The 401 is a great engine.
Put one in my son's '5' about 20 yrs ago, so he could play in the sand.
Still going strong.
For 99% of jeep'n, the 6 popper is fine.
LG

 

[Posi]

The 6cyl is a good engine and so much easier to work on then a V8.
If geared correctly the 6 cyl is all you would every need in a Jeep unless you play in the mud or sand more often then not.
I have a 6 in my 77 and I'm very happy with it as is.
The 401 is a good engine as well. The 401 has a high nickle content which adds tensile strength unlike the AMC 304 /360.
The 401 will get you out of some slick spots with the skinny pedal but you need to make sure all else is up to snuff.
The 8 will throw off more heat and you'll stop at the pump more often.
Price you pay for owning a 401.
With my 401 I can pretty near lift the front tires off the ground in my 3B on a 3/4 throttle takeoff (full dis-closer - SOA front/flat springs).
You will never sneak up on anyone.
401 has a cool factor, different levels for different folks.

 

[Rockratt]

Like most Jeep engines the AMC 258 i6 / 4.2l is not seat of the pants impressive but is still probably my favorite engine. Add a descent cam, Weber carb and some gears on top of 33 inch and plus tires , it will break more parts offroad than most people want to replace.
The 401 is the dream setup but the factory running gear will never handle it if you use the skinny pedal much at all.

 

[Colorado Yeti]

I think the AMC 258 i6 / 4.2l is a great offroad / townie engine but is an utter dog above 40-50 mph. I hated driving our 1981 6-cylinder CJ7 up any mountain passes because I would get passed by everything. I have a 1976 CJ7 with a tired AMC 304 and it still flies up any passes doing 75-80 mph and still has 1/4 pedal left in it. I'm building a 401 for it now.

By the way, I did a 360 V-8 swap in our 6-cylinder '81 CJ above and our gas mileage actually increased because i didn't have to have my foot buried to the floor all the time to get it to go down the road.

To get back to your question, I would pay $2000-$3000 premium for a V-8 CJ. But that's me and I frickin' love V-8's. I would pay that premium just for the sound alone!!!

 

[Lumpy Grits]

I think the AMC 258 i6 / 4.2l is a great offroad / townie engine but is an utter dog above 40-50 mph. I hated driving our 1981 6-cylinder CJ7 up any mountain passes because I would get passed by everything. I have a 1976 CJ7 with a tired AMC 304 and it still flies up any passes doing 75-80 mph and still has 1/4 pedal left in it. I'm building a 401 for it now.

By the way, I did a 360 V-8 swap in our 6-cylinder '81 CJ above and our gas mileage actually increased because i didn't have to have my foot buried to the floor all the time to get it to go down the road.

To get back to your question, I would pay $2000-$3000 premium for a V-8 CJ. But that's me and I frickin' love V-8's. I would pay that premium just for the sound alone!!!

Much of that 'dog' comes from your R&P ratio.
Along with the condition of the engine(blow-by etc).
I have no issue run'n 65-70mph on level ground in mine.
LG

 

[Colorado Yeti]

Much of that 'dog' comes from your R&P ratio.
Along with the condition of the engine(blow-by etc).
I have no issue run'n 65-70mph on level ground in mine.
LG

You are absolutely correct there my friend. The '81 CJ7 I was referring to had 2.73 gears, which is absolutely criminal in a Jeep no matter what engine you run.

The argument is a no-win on both sides. I will probably never convince the AMC 258 i6 / 4.2l fans that a V-8 is better and I would never think of owning another 6-cylinder CJ after owning ~ 30 CJ's in my life, some with 6-cylinders and some with V-8's. To each their own...I love all CJ's no matter the flavor.