V8 to 4.2 swap questions

[Bunky67]

I'm getting ready to swap out my AMC 304 for an AMC 258 i6 / 4.2l AMC 258 i6 / 4.2l 6 cylinder my Jeep is a 77 and the engine is a 1985. I have a 3 speed manual in my CJ5

I would like to use my carburetor, and radiator at least. I know the flywheel is different.


Do I have to change the frame mounts?

Is there anything else I need to do or change?

 

[Saddle Tramp]

The passenger side motor mount will need to be relocated (driver’s side is the same) but if you are careful when removing the mount from the frame it can be reused. The engine to bell housing bolt patterns are the same between the CJ I6 & V8 so you should be able to just bolt right up.

 

[Jimbos76cj]

I'm getting ready to swap out my AMC 304 for an AMC 258 i6 / 4.2l AMC 258 i6 / 4.2l 6 cylinder my Jeep is a 77 and the engine is a 1985. I have a 3 speed manual in my CJ5

I would like to use my carburetor, and radiator at least. I know the flywheel is different.


Do I have to change the frame mounts?

Is there anything else I need to do or change?

Like already said one side frame mount is different. The only other thing to look at is the attachment point of your Z-bar.. I think it bolts to the Transmission so it should be the same. yes you will need a different flywheel. Make sure you have the ignition module and parts from the AMC 258 i6 / 4.2l when you install it into the CJ.

 

[duffer]

Why????? Even if I had a good AMC 258 i6 / 4.2l I wouldn't do that swap. Find a 360 and bolt it in.

 

[Bunky67]

Why????? Even if I had a good AMC 258 i6 / 4.2l I wouldn't do that swap. Find a 360 and bolt it in.

I don't need the added power, and I just like the AMC 258 i6 / 4.2l and it was cheaper and easier then finding a good 360

 

[OldC7]

Cant help on the swap but I like the AMC 258 i6 / 4.2l much better than the 360 also.

 

[coldair]

The AMC 258 i6 / 4.2l is a great motor for a jeep.

 

[Bunky67]

As far as the Clutch Will the 77 AMC 304 Clutch disk and pressure plate bolt to the AMC 258 i6 / 4.2l or do I have to buy a new pressure plate and Disc ?

 

[fuzzy]

Bunky, I am doing the I6 to V8 swap, I have the frame and engine mounts/ frame brackets you need and you have the brackets I need, maybe we can swap or I will buy your frame and engine brackets from you. Just reply to this post if interested... Thanks

 

[Bunky67]

Fuzzy
I haven't even started pulling my engine and my frame mounts appear to be fabricated, not original, (my CJ5 had a frame off restoration a few years back) so I can't really help you right now, Sorry

I would like to see a photo of your passenger side mount if this is possible

 

[79cj7bogger]

Same swap was done to mine before I got it. Went from 79 AMC 304 to 77 AMC 258 i6 / 4.2l wiring was redone clutch flywheel motor mounts. And a single barrel carb was put on same radiator though

 

[79cj7bogger]

One thing I would recommend if your rebuilding the AMC 258 i6 / 4.2l get a hedman. Dual port header and wrap them

 

[coldair]

How about you swap in a 4.0 head and put an 4.0 header on the AMC 258 i6 / 4.2l ?

 

[79cj7bogger]

Can't remember what it is but my buddy is thinking of doing a 6 equals 8 set up

 

[coldair]

Can't remember what it is but my buddy is thinking of doing a 6 equals 8 set up

Clifford proformance is what your looking for. I waited 3 months for them to grind a cam for my AMC 258 i6 / 4.2l I got tired of waiting and ordered a comp cam.