Swapping 258 for a 304

[Georgia Jeep]

I have an excellent AMC 304 in my 73 CJ5 and my 77 CJ5 has a "tired" AMC 258 i6 / 4.2l . Besides changing the motor mounts, is there anything anyone can think of that I need to be concerned about. I'm wondering if the leaf springs,the Transmission and Transfer Case can handle of 304. The 77 is not used for off road, it is used simply for driving around town.

 

[Saddle Tramp]

Go for it. Other than relocating the passenger side motor mount plus a few minor wiring mods and the like the 304 will easily swap over as the motor to bell housing bolt pattern is the same for all the AMC I-6s and V-8s allowing you to mix and match just make sure to use the proper pilot bushing for your transmission. Most likely you have either a T150 or a T18 in your 77 which is about as good as it gets from the factory.

 

[73CJ]

Unless the 73 is in bad shape, there are many good things in the 73. Dana 44 axle, bigger Transmission access cover.
Q
The 73 should have a T-15 and a Dana 20 Tcase. 77 would have had a T-150 and a D20. I've seen plenty T150s fail behind a AMC 258 i6 / 4.2l . I don't care for the T-AMC 150 .

You could drop the whole drivetrain in the 77. Better swap in the D44 rear axle as well. Tha AMC20 can/ will spin an axle with a V8.

 

[Saddle Tramp]

Unless the 73 is in bad shape, there are many good things in the 73. D44 axle, bigger transmission access cover.
Q
The 73 should have a T-15 and a D20 Tcase. 77 would have had a T150 and a D20. I've seen plenty T150s fail behind a 258. I don't care for the T-150.

You could drop the whole drivetrain in the 77. Better swap in the D44 rear axle as well. Tha AMC 20 can/ will spin an axle with a V8.

Actually the T14 was used behind the AMC I-6 in a CJ through 1975 but the 304. The T14 is considered for the most part a lighter duty transmission. The T150 as far as coming unglued due to power isn’t bad and would hold up better than the T14; at least that is my opinion. The frame on the 77 is better than the 73 and the Dana 44 in the 73 could be swapped into the 77 too.

 

[CJim7]

You'll need to relocate the fuel line to the driver side. I simply extended it from its current location and crossed it over at the front crossmember, just along the base of the radiator.
Obviously, your exhaust will need modified. You shouldn't have to change driveline lengths. The radiator should be swapped out.

 

[xena1]

Go with the MORE Bombproof motor mounts. A little costly, but makes the job a whole lot easier. One piece from block to frame. I also used an aluminum cross-flow radiator which keeps the 360 cool even in the hottest weather

 

[Georgia Jeep]

When I bought the 77 it was literally in pieces (see pics). I spend a couple weekends putting it back together (to take stock in what I had). Bought a wiring harness out of an 83 and modified it to fit the 77. Then I fired it up (I expect this was the first time it ran in several years). At this point I knew I had something to work with. After careful thought, I sold the 73 with the AMC 304 . The AMC 258 i6 / 4.2l just made better sense for what I wanted it for.

I have decided to do a complete frame off restoration and the work has already started.

 

[Georgia Jeep]

Assembled the Jeep from a million pieces.....cranked it then turned around and disassembled everything to begin the restoration......

 

[Georgia Jeep]

Sent the motor out to a machine shop to get all of the machine work done....60 over on the bore, 20 over on mains and connecting rods, standard cam, new cam bearing, new pistons, new oil pump, new valves, water pump, fuel pump, thermostat....

 

[Georgia Jeep]

While the motor was out to the machine shop I decided to do a little repair on the tub...

Cut out the bad stuff and welded in a Classic Enterprises patch panel....

 

[thiswontbetooexpensive]

Looks great!