New Engine?

New Engine?


Ames, IA
1975 CJ5, Basically stock except for electronic ignition.
My Jeep has a standard 232 6 cylinder with a T14 transmission. I am thinking about finding an old 258 and rebuilding it from the ground up. Bore it out, a healthier cam, intake manifold, headers, probably a Holly carb. Just soup up a 6 cylinder instead to stuffing a V-8 engine in there. Is this a good idea? Would it be worth the effort? Keep in mind this is something that I would be doing just for fun. I could work on the engine for as long as I wanted to or as long as my stock engine lasts. Just tell me if I'm crazy or not. If not, would a different transmission be in the mix? Thinking that maybe a four speed would be a better match. I know this is probably way out there. I'm just playing around with it in my head right now.
I was thinking of doing the same thing. But keeping my auto tranny. My thought is it would be an easier swap, plus I won't have to worry about having so much power. Don't want to break drive line parts while out wheeling

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How much are you wanting to spend on soaping up a 258? I love the 4.2 motor they are a great motor! If your looking at getting a straight 6 I would go with a 4.0. If I knew how much I was going to spend on my built 258 I would have gone with a 4.0 and stroked it.
If your wanting to know how much I spent on mine PM me and I will tell you.
Now I'm not trying to tell you not to build a 258. My 4.3 is supposed to be rated at 225 hp
289.9 torque at the fly wheel. I do mean 4.3 because I bored it out 0.030
Just soup up a 6 cylinder instead to stuffing a V-8 engine in there. Is this a good idea? Would it be worth the effort?
I think it's an excellent idea. Just don't get high expectations of horsepower out of that 6.

I have had a 258 and a 304. I think they are both great engines. That 258 could roll over rough terrain at idle speed, without giving it any gas.

I like the list of mild modifications you mentioned. Just don't go gonzo with turbo, high compression or anything like that. If you want big block horsepower get a big block but then you'll be opening a whole other can of worms. A few months ago a magazine had an article about someone that got several hundred horsepower out of a AMC strait 6. It was insane but it doesn't sound like you are out to set any records.

Keep in mind the intended use of your jeep. Jeeps are made for off-road. Beware of parts that promise high horsepower. High horsepower comes at high RPMs. When selecting a cam and intake make sure you will still get the low end torque.

Good luck and keep us posted.

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