Engine 258 w/ cracked block... What Now?

[Bburkes419]

I have a 78 CJ5 AMC 258 i6 / 4.2l with a T-18 Transmission . I was getting ready to change out the exhaust manifold and discovered, under the manifold on the side of the engine block, a crack running from freeze plug to freeze plug. I have had this jeep for 4 years and put a ton into it. I couldn't figure out how I missed it. Well, it looks like it was covered with JB Weld, and it finally broke free. Under the shadow of the manifolds, the weld must have blended in with the block pretty well.

So, where to now? I have debated on trying to keep it as close to original as possible and getting a remanufactured AMC 258 i6 / 4.2l . However, a buddy of mine has suggested finding an LS motor. Thoughts?

The LS would obviously have more power and could be quite fun. I am very much leaning in this direction. So, any advice, things to watch for, things to watch out for would be appreciated.

Thanks,
Brett

 

[Manic Mechanic]

Unless you can do the work yourself and you know the motor doesn't need rebuilt you can easily get 20k deep in this swap. You will definitely need a new Transmission , drive shafts and fuel system. Possibly axles as well.

Cheapest fastest way would be a replacement AMC 258 i6 / 4.2l even a used one that needs rebuilt would get back on the road faster and vastly more affordable than an LS swap

 

[Apple]

I would look into fixing the crack if it is the only one or find a replacement short block and rebuild the head and put it back together.