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Unread 07-04-2008, 04:47 PM   #1
SilverRubiSC
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Pros and cons of 360 swap versus 304 swap

Hey guys,

Im looking at an 85 CJ7 that has an AMC 360 swap. The 360 was taken out of a J10 truck and rebuilt. Just curious what the advantages and disadvantages are of having the 360 instead of the 304. I see more 304 swaps so is there something I should look for before buying the one with the 360? As far as overall horsepower what is the difference? Im sure the gas mileage is about the same which is not a big deal. Any advice would be appreciated!!!

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Unread 07-04-2008, 06:00 PM   #2
SuB8HaVeN
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Gas mileage should be about the same, but the AMC 360 V8 will make much more power than the AMC 304 V8. IMO, the 304 V8 really isn't too much of an upgrade over the 258 I6.
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Unread 07-04-2008, 06:05 PM   #3
BESRK
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The 360 will have all the advantages of a 304 PLUS more power. No disadvantages over a 304.
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Unread 07-05-2008, 07:37 AM   #4
The Keith
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The 360's power will make weak spots in the drive train even more weaker. The 258 and 304 spec's are pretty close to each other, but the 360's torque and HP numbers would make me wince if it was pushing my stock set up.
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Unread 10-09-2009, 08:01 PM   #5
Jeremy_C
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I think Im gonna have to go with the 360, although I've heard different things about it. Mainly the Gas MPG, some say you'll get as low as 5-8mpg, and others say they get upwards of 15-18mpg.

My jeep is lifted 4inches, 35x12.50 tires. I guess it has stock axles, I just dont want the thing breaking in half if i drop a 360 in it. lol
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Unread 10-09-2009, 09:25 PM   #6
mylittlecj5
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For the record, I have a built up 360 (done by the PO, so I really don't know whats inside). It also has a 670 TA carb, headers, CDI ignition, Teamrush'ed, yada yada yada. Stock drivetrain other than that. Running 35" Super Swampers, and I beat the snot out of it in the mud and some rocks. The only failures I've had were 1 front axle U-joint (during a race, full throttle turns) and destroyed the rear spider gears, twisting the driveshaft in the process, again during a race, (5000 RPM launch off the line). I'd say the stock drivetrain would hold up to moderate driving even with a 360.
I love the power of my 360, and would never trade it for a 304. Seems easier to get parts for it, also.

I'll start worrying about breaking the stock drivetrain when I locate and install a 401!
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Unread 10-10-2009, 12:30 AM   #7
Jeremy_C
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What I wanted to hear man. Thanks.
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Unread 10-10-2009, 04:29 AM   #8
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Another point of interest is that 304's came stock in some CJ's where as 360's did not. So there is not really a swap ratio. I have a 360 and really like it. Enjoy!!
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Unread 10-10-2009, 12:41 PM   #9
Andy5150
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I have a 360, an I love it. It ain,t a mileage champ, but its got all the power you,ll ever need, and it sounds great. As far as breaking driveline parts, a big factor is how you drive it. If you,re a person who regularly has one of those "Hey,hold my beer" moments, there will be breakage.
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Unread 10-10-2009, 03:48 PM   #10
spcmac249
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The 360 has any where from 20-50 more horsepower than the 304 and 10-20lb/ft more torque. the difference being the latter numbers are with dual exhaust.
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Unread 10-10-2009, 04:27 PM   #11
CaliDaze
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Yea I think Im going to start a 360 build. Ive put too much money into this 304 and not getting enough out of it. I think ill just beat the snot out of it while building the 360 on the side.
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Unread 10-10-2009, 06:53 PM   #12
h2ojeep
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Does everything interchange with the between the 304 & 360?

Is the MC 2100 enough carb for the 360?
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Unread 10-10-2009, 07:21 PM   #13
mylittlecj5
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all the external stuff will interchange between all the AMC V-8 engines. There are a few differences, Like different exhaust manifold bolt sizes on later 360s compared to early ones. But the good news is all the money you spent on headers and manifolds will change out to the new motor with ease.

here is a good site for ya...
Bulltear.com - Home
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Unread 10-11-2009, 07:59 AM   #14
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Quote:
Originally Posted by h2ojeep View Post
Is the MC 2100 enough carb for the 360?
If the venturi is the 1.21 (numbers located on the throttle linkage side of the carb inside a small circle).

My question is - Why go with a 2 barrel when you can enjoy 4?

Later, T.J.
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Unread 10-11-2009, 12:12 PM   #15
h2ojeep
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Quote:
Originally Posted by JavaTee View Post
If the venturi is the 1.21 (numbers located on the throttle linkage side of the carb inside a small circle).

My question is - Why go with a 2 barrel when you can enjoy 4?

Later, T.J.
Thanks for the info on the needed larger venturi. As to enjoying the 4 BBL, cant see its worth it:

AMC Engine comparison
Jeep Engine: AMC 360 V8

I used the above noted web site to compile this information. Bear with me, I’m an analyst and numbers are a second language for me, especially when put into a simple study. I am accountant/finance experienced and educated and worse still a shade tree engineer. A real engineer may “tear” up my concept up with details, but in general (just as the specs below are general); I will stand by my conclusions.
  1. Engine CU................... Bore.....Stroke......... HP@RPM...........Torque@RPM
  1. 401 w/4bbl .................4.165.... 3.68..........315...4400...........320...2800
  1. 360 w/ 4bblcarb ..........4.08...... 3.44..........195...4400...........295...2900
  1. 360 w/ 2bbl carb .........4.08...... 3.44..........175...4000...........285...2400
  1. 304 w/2bbl carb ..........3.75.......3.44..........150...3200..... ......245...2400
  1. 258 inline 6 (4.2L) .......3.75........3.9...........112...3200....... ....210...2000
  1. 232 inline 6 (4L?)..........3.75.......3.5...........100...3600 ...........185...1800
When you look at the specs of each engine on one page, there are some reveling conclusions to make. To start off, when ever you see stroke increase, generally power (torque) also increases with the same amount of energy. It is the exact same science as when you get a longer crow bar, longer thus more power to energy ratio but the other related physics also mean you are probably moving slower.

In term of jeep use, I am more impressed with the 258’s torque at 2000. I have a 304 because of the decisions I made when looking for the jeep (I wanted a 258, but found a jeep with almost no rust and a great history of being driven only 600-700 miles per year on a hunting lease for the last 16 years before I got it). But I am pleased with the 304 and would not go to the trouble to change to the 258. The 304, with the MC 2100 2 bbl carb, will get to a scary 80 mph quick enough and drive 70 easy all day long; runs great in trail conditions, so there is plenty there. I am getting 12 MPG regardless of what I do and while not great, I am OK with that.

In what I want to do with a jeep, I want my power (more so torque) at a lower end of the RPM range. My primary use for a jeep is for off road use, and I am more impressed with the torque at the lower rpm.

If I were using my jeep for street driving and getting somewhere quick, the 360 with the 4bbl would be better (by comparison) and I would be running street tires and NOT off road tires.

Off road is where my priorities lie, and I see the jeep not so much as a “quick” vehicle. (and I am not trying to be critical, my boat is a 18ft with 200hp, very quick. Again different priorities)

I was of the opinion that more 360 were made than 304 and could conclude that more parts are available for the 360. My 304 is strong and sound but now has 100000 miles and I have been thinking about getting another 304 to build up (stock).

After reading this thread, the 360 (w/2bbl) looks very good. The 2 bbl 360 with the 40 extra ft/lb of torque (285-245) at the same rpm as the 304 (see crow bar comparison above).

To pick up only 10 ft/lb of torque (295-285) by going to a 4 bbl on a 360, and the cost of 500 (2900-2400) more rpm needed, hardly seems worth it.

As to the 360, if engines and parts are easier to come by, then better still. All this as long as it would be a fairly easy exchange when “stabbing” a 360 where the 304 was.

If the exhaust headers are not the same, then maybe I need to find a 360 with exhaust headers included. Does anyone know if the exhaust pipe connections are the same between the 360 and 304?

I would love to see some specs on the both the 304 & 360 with the 401 (3.68 stroke) connecting rods if the block/ head would clear the extra stroke.

The 310 ft/lbs at 2800 rpm of the 401 looks really good (more like wow), but I could see a lot of broken parts in my future, a engine and parts hard to come by and too too frequent trips to gas er up.


And making a table on this presentation is not very easy

Last edited by h2ojeep; 10-11-2009 at 12:43 PM..
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