upgrading powerplant!!!!

hey guys,
i just recently got back from the 3rd annual Spring Scramble in the Ocala National Forest. it was an awesome event. met alot of good people and seen alot of cool jeeps. i think last count was alittle over 200 jeeps. i took my 81 cj5 which is pretty much stock except for the 32's i'm running. but it perfprm great. went anywhere the other rigs where going. so all in all good time and proud of my cj5. but now that i'm back and have some new knowledge of my jeeps capability. i am gonna do an engine swap so i can have more power in the thicker mud. i currently have a 258 with a t-176 4speed. i want to swap in a 304 from my other cj5. it is a 77 cj5 with a 304 and 3peed trans. all i want to do is swap motors. the 77 is a complete and running jeep just not in the best of condition body wise. what all will i have to do to make this work? any and all suggestion will be helpful.

 

might be easier to swap bodies

 

^^What I was thinking. I have been trying to think about what would be involved because I have had Jeeps 258's and ones with 304's. I think it would be a fairly easy swap and I wouldn't be worried about doing it. I am just trying to remember about the motor mounts and what is involved in that part. Since you have both Jeeps, it should be pretty simple. Look at what you have on the one with the 304 that you don't have with the 258 and swap those parts over.

 

I understand that you need the engine mounts (frame mounts) from the 304 chassis. Other minor things are different, like the radiator and cable routings. The 304 will bolt up to your existing T-176 bellhousing without any changes. You may need to reposition the transmission and cross-member, since the V8 is shorter than the I6.

If it were mine, I'd build up the 258. There's not that much displacement difference between the two engines, and you will get a lot of benefit from better breathing, a hotter cam and ignition upgrades. Put a 258 crank in a 4.0L block and you'll have a 276 cid I6, and use the 4.0L HO head and MPI ... more power than a 304, more reliable, better drivability and better economy. A somewhat milder combo of the 258 with GM TBI, a hotter cam, HEI and the 4.0L head should easily match the stock 304 power, and require no changes in your driveline. JMO.

 

I have a 78 Golden Eagle with a 304 in it. My cousing just gave me a good 258 but I am still probably going to rebuild it. I am just not to fond of the 304 so I was going to do a swap and put in the 258. I have a good 4.0 block though and after seeing your post this may be the way I go. I will have to keep you in mind for info if you don't mind whenever I can get around to doing it.

 

I agree, my 4.0 has more power than my 304, bottom end is great. My 304 is headed out.

 

Find a 4.0 head, weld the triangle water jackets up, put a stock 4.0 exhaust manifold on it and you have the best of both worlds. Or, take the crank out of the 258, install in the 4.0 block, and make a stroker out of it.

High5

Oops, I should have read Timgr post better. However, I agree with him all the way

 

thanks for all the advise! after pondering a bit i am gonna do one of two things. rebuild my 258 or look for a mid 90's 4.0 motor. what you all said about reliablity and economic advantage of a 6cyl. drove it home. you can't go wheelin if you can't afford the gas. lol

 

All true, but you can't beat the sound of a good running V8 IMO.

 

This is true and I will not let my 304 go to waste. Main thing for me is that I have a good 4.0 block and can get a head for it cheap that has been laying in our shop taking up space in the scrap metal bin for six months now. I have been asking myself what I could do with it. Now I know. Can't believe I didn't know it.


Oh great, I just realized something else. NOW I HAVE ANOTHER PROJECT!

 

HI-5,

How'd you get the 33's stuffed under your Jeep without a lift?