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OT, Jeep CJ7 motor

K

kennebunksawmill

Member
I drive a 1983 Jeep CJ7 with the straight 6 258 motor. I am planning on replacing my motor with a good used engine this winter (mine is just tired, I run a lift kit with oversize tires & pull a boat in the summer). My local junkyard has a good 304 Jeep motor out of a 70's Cherokee...does the 304 mount right up to my 5 speed, or do I need to buy an adapter kit?
 
Depends on the year of the 304 I think. AMC changed bell housing mounting sometime in the early 70's when they went over to the 258. The early 304, I think 70-73 I don't think will fit but later models should be a direct bolt in. Only thing you need to check is how the engines are ballanced. Some engines like the 300 Ford 6 are internally ballanced. When swapping in a 302 (direct bolt in) you also have to have the correct flywheel/torque converter as the 302 is externally ballanced. I know there are some really good Jeep forums out there so Google it.

Rick
 
You are downgrading going froma 258 to a 304, not much extra power for a lot more fuel, and a lot less pleasing torque curve. If you wanted more power I would say get a fresher 258 and look at some of the bolt-on doo-dads to make more power. In my opinion the 258 is on the top 5 list of motors, I don`t think AMC V8s made it on any lists, anywhere.
 
the Chevy 261 is the same engine. I think AMC shaved the head to drop the 3 cubic inches.
 
The 1971 and older blocks use a "small" bell housing bolt pattern that is exclusive to AMC and small Nash sixes. In 1972 the bell housing bolt pattern was changed to match the AMC V8's. The 1971 258 uses the "small" pattern, the only year 258 to do so. Bill
 
2X4, dont think so,never heard of that relationship of engine families.worked for AMC in the late 70's. this is from wikipedia.

"The company (AMC) designed an entirely new six-cylinder with a short stroke and seven main bearing crankshaft for 1964. This design was produced in various forms through 2006. "

for a start the 261 only had 4 main bearings Bill
 
You have to be careful and do your research. I know there are differences in the AMC V8 crank flanges depending on the trans the engine originally had. A Torqueflite crank can't be used with a manual trans in some years. There was also a difference if the V8 originally had a Turbo 400. I know this because I got burned once a long time ago, but can't remember the specifics.
 
(quoted from post at 22:35:04 08/24/12) I drive a 1983 Jeep CJ7 with the straight 6 258 motor. I am planning on replacing my motor with a good used engine this winter (mine is just tired, I run a lift kit with oversize tires & pull a boat in the summer). My local junkyard has a good 304 Jeep motor out of a 70's Cherokee...does the 304 mount right up to my 5 speed, or do I need to buy an adapter kit?
Click to expand...

Go ask these guys, they know their stuff.

http://theamcforum.com/forum/forums.html?SID=dc523bab8cb62c8ezz46725b78f1zf41
 
(quoted from post at 05:35:04 08/25/12) I drive a 1983 Jeep CJ7 with the straight 6 258 motor. I am planning on replacing my motor with a good used engine this winter (mine is just tired, I run a lift kit with oversize tires & pull a boat in the summer). My local junkyard has a good 304 Jeep motor out of a 70's Cherokee...does the 304 mount right up to my 5 speed, or do I need to buy an adapter kit?
Click to expand...

I have installed a late 70's 304 in a 87 wrangler,,, the 304 bolted up to the trans with a special pilot bushing but the rest was a nite-mare... Its not a EZ conversion and a waist of money,,, either stay with you 6 are use a 350 chevy,,, you can buy all that's needed for the chevy swap conversions are geared that way :wink:

Nuttin wrong with your 258 add GM HEI and GM a throttle body injection set up... A AX15 conversion is well worth the expense... I just did a 83 CJ7 with a 258 that had a Dana 300 transfer case...
 

How about a 242 (4.0l) block and head with a 258 (4.2) crank and rods. Cute little 4.5 "stroker" that will fit like a stock motor and run a little faster.

Tommy
 
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