To Rebuild Or Replace?

[n4thornton]

Ignoring cost, I'd like to get everyone's opinion on the best route for my 85 CJ. I'm doing a full tear down and rebuild of the vehicle but I'm not sure which direction to go with the engine. I'm considering replacing the AMC 258 i6 / 4.2l with a 350 small block but, have also thought about just rebuilding the AMC 258 i6 / 4.2l ... The Jeep is not a daily driver and will be used for the occasional run up to the dunes, some mild offroading but nothing too crazy. Is it a waste to spend the extra money to put the 350 in for what I will be using it for?

 

[mdeluca]

AMC 258 i6 / 4.2l ... It is more than just swapping in the v-8. The rest of the driveline will need to be beefed up as well... brakes included. That is my understanding anyway.

Except for maybe the dunes, the AMC 258 i6 / 4.2l will do it. Its no sprinter. We cruise the mountains, light off-road, exploring, camping and the AMC 258 i6 / 4.2l is more than adequate.

 

[RiverandSand]

The engine swap while not cheap it is very satisfying. If you choose to go V8 the least expensive route would be the AMC 304 -360, will drop in with the least amount hassle as earlier jeeps came with the AMC 304 . The T-4 or T-5 Transmission are weak and should to be swapped out though, the auto Transmission will bolt up to the AMC motors and can used. The Dana 300 TC, Dana 30 front axle and AMC20 will handle the added power. Novak is a good site to read up on jeep engine swaps, it will give you good idea what is involved.

 

[gert]

I love the originality of having an AMC motor in a Jeep over swapping another manufacturer engine in, the AMC 258 i6 / 4.2l really is a great reliable engine.

To have some fun and more power you can grab a complete 4.0 with harness and make a 4.6 stroker using your crank and it would be fuel injected to boot


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[cglax6]

The engine swap while not cheap it is very satisfying. If you choose to go V8 the least expensive route would be the AMC 304 -360, will drop in with the least amount hassle as earlier jeeps came with the AMC 304 . The T-4 or T-5 Transmission are weak and should to be swapped out though, the auto Transmission will bolt up to the AMC motors and can used. The Dana 300 TC, Dana 30 front axle and AMC20 will handle the added power. Novak is a good site to read up on jeep engine swaps, it will give you good idea what is involved.

When Uncle Sam decides to start paying me again, I'll be able to continue working on my 351w engine swap. I currently have a recently rebuilt AMC 304 in it if you're interested and can wait a few months. It has a little over 3k miles on it and runs just fine...please don't judge me! I'll be parting with my T-18 because I already have a Ford T-18 ready to go for the 351w.

 

[n4thornton]

I love the originality of having an AMC motor in a Jeep over swapping another manufacturer engine in, the AMC 258 i6 / 4.2l really is a great reliable engine.

To have some fun and more power you can grab a complete 4.0 with harness and make a 4.6 stroker using your crank and it would be fuel injected to boot


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I agree, having the original AMC 258 i6 / 4.2l in there is a draw for me, not to mention the impact on my wallet. Cleaning up the original and adding some mods for a little more power might be just right, however, watching videos of guys dropping the 350 in the CJ really gets me thinking....

 

[Kane]

For ripping dunes you need the 350. I swapped one in my CJ5 and built the motor pretty good. The power in a light weight CJ5 was ridiculous. I bought a CJ5 that was already converted and swapped everything around and then sold that Jeep with my old drive-line for the same price that I paid for it. If you want to have fun on the dunes then even a bone stock 350 will be worth it.

 

[Lumpy Grits]

Ignoring cost, I'd like to get everyone's opinion on the best route for my 85 CJ. I'm doing a full tear down and rebuild of the vehicle but I'm not sure which direction to go with the engine. I'm considering replacing the AMC 258 i6 / 4.2l with a 350 small block but, have also thought about just rebuilding the AMC 258 i6 / 4.2l ... The Jeep is not a daily driver and will be used for the occasional run up to the dunes, some mild offroading but nothing too crazy. Is it a waste to spend the extra money to put the 350 in for what I will be using it for?

Get an AMC v-8. It's pretty much a bolt in deal.
LG

 

[gert]

Get an AMC v-8. It's pretty much a bolt in deal.

LG

Yep that’s what I did and you can go straight to the parts store for your swap parts and the 360 is really powerful


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[Manic Mechanic]

im partial to the AMC 258 i6 / 4.2l myself i use mine for road cruising and off roading and rock crawling. its a great motor just do a few simple upgrades like gm hei ignition and dump the carter carb for either a ford mc2100 or fuel injection

 

[n4thornton]

Get an AMC v-8. It's pretty much a bolt in deal.
LG

Well now you got me thinking.....Any specifics on what else would need to be upgraded? Driveline? Engine mounts?