Engine Swap

Ok so i have to much time on my hand (have not worked in 2 weeks) back to work soon

I found a 1975 CJ5 Jeep
It has a V8 in it. I just cant justify feeding a V8
How hard would it be to drop a inline 6 in it???


Will the six bolt directly to the V-8’s transmission, or will an adaptor of some kind be necessary?

Probably not too terrible difficult. An I6 was a factory option (the AMC 4.2L I6 I think) You might have to change the motor mounts, but the Jeep should be pretty easy to work on. I don’t think you’re going to save enough in fuel to justify the costs involved in the swap though. The AMC straight 6 wasn’t particularly fuel efficient.

Unsure about adaptor.

Any idea about the difference in fuel efficiency ??

Not sure, the economy is more a function of the gearing and the brick-like shape. Is the v8 in good shape? Good compression? I’d think you might do pretty well getting it in tune, maybe put a good small bore 4 bbl on it, and same a LOT of time/money.

What’s the V8/carb setup in it now and what’s the 6 you’re thinking about?

You might consider a more common engine and transmission, say, GM, Ford, or Dodge. Iti will be easier to get parts in the future.

This engine should be a 304 AMC V8 unless somebody put a Chevy (very popular swap) in it. They were not known for being very fuel efficient (or lightweight either) but were hard to break. Rather than swap in a nearly 40 year old AMC big (258 cid) or little (232 cid) six which was available in those years would you consider upgrading the V8? This assumes it is in good shape to begin with.

You may be better off to swap the carburetor for an aftermarket fuel injection system. Holley Pro-jection (others are available) systems can be fitted to this engine and can make a big gain in economy, driveability and power. $1200 is a lot to spend but you’ll drop most of that putting in the six and won’t be as happy.

Its a big deal to put a 6 were the V8 is. The big problem is the motor mount (ie stand) is welded to the frame on Jeeps. To put a 6 you have to cut the mount out and replace it with one you cut from a Jeep with a 6. You wont gain any MPG with a 6. They get about the same. The motor to trans is not a problem. Just get a the 6 with the bellhousing and you are good to go. Oh to anybody that thinks that parts are to get for the or any of CJ type Jeeps is wrong. You can bulid one all new from parts if you want to spend the money. You want new body to any nut or bolt, it can be bought.


If you don’t want a CJ with a V8, why don’t you just buy a Cj with the 258 already in it?

Because its a nice jeep and the price is right. But still looking for the straight 6. I am a believer in inline motors

If economy is ALL you care about, you could try swapping an Iron Duke 4 into it. Standard power plant on postal Jeeps.

Drop a good 4.0 High output in it,should make a good package-Kevin

love the 4.0 high output