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Discussion Starter #1
Hi all. I have a few questions about which engine I should put in the wife's CJ7 Jeep. I'll be fixing it up for her as it has sentimental value. No mudding, and only light to medium trails. We don't have any real interest in doing the difficult trails. The jeep has no engine or trans. I think it may be easiest if I just number these questions. So here they are:

1. Is there any reason I should use the ford inline 6 instead of the jeep 4.0L inline 6? The Ford is 300 ci, a 4.9L. That's even more than if you stroked and bored the Jeep 4.0L to a 4.7L. And I imagine that the Ford's torque is low in the rpm range, just like the Jeep engine. So if I went with the Ford, would I be getting a somewhat better engine? Whichever engine I end up going with, I do want it to have more than enough horsepower for the highway. That way we can drive the thing to the trails and not have to pull a trailer. I don't know how much the Ford 300 engine is known to make, when you leave it naturally aspirated. The Jeep engine is also a bit of a turd when it comes to horsepower though.

2. Should I go with a GM Atlas 4200 instead? They could be found in trailblazers and Envoys until 2009. It's another inline 6 engine, but of course more modern and making a good deal more power than the older Ford or Jeep engines. Apparently it's not difficult to make an Altas see 300hp/300tq naturally aspirated. Which are the numbers I'd like to see. I don't know if the old Ford and Jeep engines are going to do that very well. The Atlas is also all aluminum, but I'm not sure if that's any real help in a CJ7. It's probably a safe bet that it gets better gas mileage than the Ford or Jeep engines too.

3. Should I just do a V8? What are the main concerns when building a rig like this CJ7 that will only see light-medium trails? I like the idea of the inline-6 because you imagine that there would be more room under the hood. Nicer if you need to work on it. But if I want 300hp and torque, is a V8 a better choice? Road manners are also a concern here. It's her Jeep not mine, and I need to build it in a such a way that she enjoys driving it. A loud, shaky engine isn't the way to do that. If at all possible, it needs to be smooth and quiet.

4. What is the potential of an NA Ford 300 inline 6? Is it unlikely I could reach 300hp/tq with one of those, if I stay naturally aspirated? Does it have better potential than the Jeep 4.0L? And what are we talking about in terms of price, to build/buy a nice Ford 300?

Anyway those are my questions, thanks!
 

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There's not that much room under the hood of a CJ with an inline 6 of any flavor. In my opinion, the 300 is possibly the most over-rated engine Ford has ever produced, the folk lore surrounding them is just silly. They're a good engine, but they don't really do anything a 302 won't. The Jeep 4.0 is a great little engine, but they aren't exactly a powerhouse. If you're looking for an easy 300hp you're in for an uphill battle with either one. The 4200 is also great, it also really poorly supported by the aftermarket.

IMO the obvious answer here is a 289/302 if you want a Ford and you want 300hp easily. The parts to bolt a 302 into a CJ have been around for decades, they're cheap to make power with and they're a very compact engine that isn't bad to work on in a Jeep.
 

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Discussion Starter #3
I think the Ford 300's reputation comes from longevity. It certainly isn't power. You hear about people with 700k and 800k miles on them, and the vehicle still runs and drives. I was just curious if one could be made to make enough power for this jeep without a turbo.
 

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300 makes decent power when massaged. 302 fits WAY better in a CJ. 302 is a go to for short or tight engine compartments.
 

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Years ago a friend had about a 1967 or 1968 Ford Galaxy (huge car) with a 300 I6. He had a small Holley 4 barrel, headers, and a small cam and would hurt the feelings of many a v8 owner. His car would not outrun much of anything, but was so close that you had to go home and work on yours to widen the gap. So don't dismiss the 300 too soon.

That being said, I'd put in a 289/302 and call it a day. Light as a CJ is, it will be fun and given that the CJ is tall, narrow, and short, will certainly be, uh, exciting to drive. BTW, if you roll your own, try toget some early 289 heads. The later 302 heads had the ginormous Ford smog bump in the exhaust ports. The early ones did not have this and those 289s would outrun the 302s most of the time.
 

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Discussion Starter #6 (Edited)
You guys gave me an idea!

I've got a 1994 Mustang GT that I'm fixing up, as I'm a fan of the first gen SN95's. It's got a 5.0L in it! I want to do a Coyote swap in that car because, well, these old engines just don't measure up to the vicious Coyote. 750hp with an added supercharger. The old stuff has been replaced. Oh well, it was bound to happen eventually, just as one day it'll happen to the Coyote.

However, that old 302 may be just the ticket for the Jeep CJ7 once it's been rebuilt. It's got lots of low end torque just like the 4.0L would have. This could save me a lot of money as I already have the engine, and there's really not much wrong with it. The car runs and drives fine and it doesn't leak anything. Only thing is... it does have 178k miles on it. So I don't think I'd feel comfortable putting it in the Jeep without a refresh. Plus, you'd wanna add some power if you had it out of there. Aluminum heads and a cam, and whatever else you needed to go along with that.

If I'm gonna go with a V8, then I want to make 350hp and torque naturally aspirated. With fuel injection. Does anyone have the build for sheet for that? Which heads, cam, intake, etc will for sure make 350hp/tq 302? (again fuel injected)
 
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