Fuel Economy difference between 304 and 360

[Canadian CJ 7]

I am curious if there would be much of a difference with fuel economy between the AMC 304 and AMC 360? I am still on the fence deciding between the two engines to replace my AMC 258 i6 / 4.2l . I be happy with a engine around 225-250 hp for the my jeep and I know the AMC 304 would be up to it. I have a AMC 304 waiting on a engine stand to be rebuild, but I have come across a few 360's. I plan on putting in a T-176 Transmission and 355 gears and will be running 31 inch tires and a Edelbrock 600cfm 4bbl. What do you guys think?

Cheers, Brian

 

[gert]

Sounds like you have made the deceision if you already have a AMC 304 . A 360 will make more torque. If you only want 250hp and already have a AMC 304 go for it

 

[Old Dog]

It would seem that at the same RPM, the bigger the cid the more gas it would use.
But thats just logic speaking. I could be all wrong.

 

[Canadian CJ 7]

It would seem that at the same RPM, the bigger the cid the more gas it would use.
But thats just logic speaking. I could be all wrong.

Your not wrong Old Dog, makes total sense, that's why I ask you guys advice, my wife is no help to me in that department. lol.

Cheers, Brian

 

[Canadian CJ 7]

Sounds like you have made the deceision if you already have a AMC 304 . A 360 will make more torque. If you only want 250hp and already have a AMC 304 go for it

Hey Gert, I got the a complete AMC 304 for cheap $275 a while ago. Everyone says the heads don't breath well on the AMC 304 . There are some 360's around for sale, I was just thinking would I have to spend a lot on head work to make power on the AMC 304 , when the 360 heads have the bigger valve dogleg heads. Would it be cheaper to rebuild a 360 over a AMC 304 to make power in the 225 to 250 hp range. I am thinking a stock 360 would make that power on it's own, just add a RV cam, intake, 4bbl and headers and your more than there, I know doing this to the AMC 304 would wake it up also. Decisions, Decisions.

 

[coldwater]

So, are you building a racing mud bogger where you need high rpm's and high flow heads with monster torque and big horses? Or do you just want a V8 CJ. You have to realize that at some point, you're not pushing a 9,000 lb one ton truck or a 4,000 ld 1967 muscle care here. It's a tiny little tin cup of a CJ that is easily too over powered for it's own good, unless your racing it. A stock build on a AMC 304 will make a pretty stout and strong running engine. If you're going for big cubes big torque and big hose numbers, you shouldn't be asking about fuel economy! If that's what you're after, better stick with the torquey and efficent AMC 258 i6 / 4.2l . There's no middle ground where you're looking.

 

[IOPort51]

If you want a V8 I would say that Karma has brought you a AMC 304 , use it.

 

[Canadian CJ 7]

Thanks Coldwater for the reality check and kick to the bad side. lol.

Thanks IOPort for the advice to use what I have already.


It settled AMC 304 it is.

 

[coldwater]

Thanks Coldwater for the reality check and kick to the bad side. lol.

Thanks IOPort for the advice to use what I have already.


It settled AMC 304 it is.

Well, in the end, it is YOUR jeep, and you can and should make it yours. But It's pretty easy to get caught up in the "I need this!" lane, and go speeding off into !!!!$$$$!!!! land. That stocker AMC 304 will haul that little jeep like crazy, and If I were inclined to have a V8, and had the AMC 304 , that's what I would use.

 

[priceg]

I noticed on Wikipedia, depending on year model of the engine, the AMC 258 i6 / 4.2l had equal torque ratings to the 5.0.

 

[coldwater]

I noticed on Wikipedia, depending on year model of the engine, the AMC 258 i6 / 4.2l had equal torque ratings to the 5.0.

It has always come neck and neck with a AMC 304 on torque. Also, If I remember correctly, it builds it in a more usable rpm than the 8 as well.

 

[IOPort51]

I always find it amusing when someone used the phrase "fuel economy " and CJ in the same breath.

 

[gert]

Hey Gert, I got the a complete AMC 304 for cheap $275 a while ago. Everyone says the heads don't breath well on the AMC 304 . There are some 360's around for sale, I was just thinking would I have to spend a lot on head work to make power on the AMC 304 , when the 360 heads have the bigger valve dogleg heads. Would it be cheaper to rebuild a 360 over a AMC 304 to make power in the 225 to 250 hp range. I am thinking a stock 360 would make that power on it's own, just add a RV cam, intake, 4bbl and headers and your more than there, I know doing this to the AMC 304 would wake it up also. Decisions, Decisions.

On my CJ I was not satisfied with the lack of power my wornout 6cly had so I decided to go to an AMC V8 I was looking for the AMC 304 but settled on a 360 instead it has gobs of torque and horsepower with a 2bbl. I beleive you will be quite happy with a AMC 304 and have less broken parts at the end of the day,I also dont see what is wrong with swapping to some 360 heads if you want the better flow.?

 

[Canadian CJ 7]

Well, in the end, it is YOUR jeep, and you can and should make it yours. But It's pretty easy to get caught up in the "I need this!" lane, and go speeding off into !!!!$$$$!!!! land. That stocker AMC 304 will haul that little jeep like crazy, and If I were inclined to have a V8, and had the AMC 304 , that's what I would use.

Hi Coldwater, I had the AMC 304 in my 79 CJ7 and loved it. It was mildly done up, with Edelbrock components. I have the AMC 258 i6 / 4.2l in my current jeep, it's got lots of torque, but it doesn't have the get up and go like my V-8 had and I don't expect it to, because both engines are like apples and oranges. I guess watching the video of Scribes 79 CJ5 with the 360 on You Tube and being in my brothers 1973 CJ5 with a 327 Chevy as a kid and him banging the gears on the street had me thinking bigger is better but at what cost. If I am getting 8 mpg out of a 360, that would take some of fun out of it. I know there is some Jeepers out there that the 360 isn't good enough and try to fit a 401 in there Jeeps. I don't want to fill up my Jeep every hour I am driving it.

Thank you for your advice and I will rebuild my AMC 304 and give up on the 360. I think with me putting one piece axles and changing the gear ratio to 355 from 273 and rebuilding the AMC 304 with a Edelbrock cam, timing set, intake and headers that it will get up and go like my old CJ. For this year and probably next I will use the AMC 258 i6 / 4.2l and have memories with this engine, but I do miss my V-8.

 

[CJ]

~~~I also dont see what is wrong with swapping to some 360 heads if you want the better flow.?

!!! 360 heads on a AMC 304 will require cylinder notching, if you do not do this the valves will hit the cylinder wall.

 

[Canadian CJ 7]

On my CJ I was not satisfied with the lack of power my wornout 6cly had so I decided to go to an AMC V8 I was looking for the AMC 304 but settled on a 360 instead it has gobs of torque and horsepower with a 2bbl. I beleive you will be quite happy with a AMC 304 and have less broken parts at the end of the day,I also dont see what is wrong with swapping to some 360 heads if you want the better flow.?

Hey Gert, I know there are some clearance issues with putting the 360 heads on a AMC 304 , I have thought of that. Some people have put in bigger valves in the AMC 304 heads and have worked well. I guess I will investigate that more more when I get to that stage of the rebuild. I want the Jeep to be reliable and I'd be happy to be in the 225-250 hp range. The more torque and Hp I have the more things are likely to break because I have a heavy foot at times. I know I would enjoy the 360, because I like speed and power like most guys, but I have to be realistic to the cost of breaking stuff, which I would probably do. The Jeep will not be like my bullet proof Chevy 350 in my Nova SS that I poured 4 grand into the engine a could rev to 7500 rpm. Once you had that power and get up and go you miss it, but there is always a cost. It crossed my mind a few times at the time to put the 350 in my Jeep, but I didn't.

Cheers, Brian

 

[Canadian CJ 7]

I guess I should change this post heading from Fuel Economy between AMC 304 and 360 to Deciding between AMC 304 and 360. LOL. Thanks guys for your advice and suggestions. I am enjoying the process of restoring my CJ as well bouncing my ideas with you guys.

Cheers, Brian

 

[lukemon]

Set that AMC 304 up with an edlebrock intake, cam, carb, and some through the fenderwell headers with glasspacks and turn outs, and you'll have enough power to get some serious speeding tickets.

 

[Canadian CJ 7]

Set that AMC 304 up with an edlebrock intake, cam, carb, and some through the fenderwell headers with glasspacks and turn outs, and you'll have enough power to get some serious speeding tickets.

Hey Lukemon, is your AMC 304 set up with Edlebrock components and headers?

 

[CJ]

With very little work, a AMC 304 will wake up. The restriction they have is breathing. I sand dragged a AMC 304 for years.

Lunati cam, ported, Torquer II intake and other go fast goodies. It would scare you! AMC's need to breath! Gulp the air in...