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304 Vs. 258 Advantages

Discussion in 'Intermediate CJ-5 and CJ-6 Tech' started by Everett Reed, Nov 28, 2018.

  1. Nov 28, 2018
    Everett Reed

    Everett Reed New Member

    Southeast Missouri
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    First let me say, I'm not trying to start a fight. I am only trying to decide which direction to go.

    I have a '74 with a rod thrown out of the side of a 232. I own a 258 out of a '77 and a 304 out of a '73 as optional replacement engines. Either option will be rebuilt prior to install.

    I've never owned a Jeep with a V8 and have never seen the need for anything more than the I6. I also know the 304 is extremely popular with the jeep crowd.

    Is there any advantage to the stock 304 over the 258?
     
  2. Nov 28, 2018
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
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    258 is a great engine.. I have never had one, but a buddy of mine did. He never had any trouble with it. There seems to be plenty of support for it, more than the 304. I had a cj5 with a 304, never had any trouble with it either.

    The later 304 and 258 had similar HP ratings...
     
  3. Nov 28, 2018
    rejeep

    rejeep Sponsor Sponsor

    Rochester, NY
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    if you are rebuilding, the 304 wins hands down..
    you can do a lot more machine work for little money and get more bang for buck results..

    I built a high dollar 258 years ago in my YJ.. biggest mistake ever!!
    for the money I put into it I could have done aluminum heads and bore out a 304 to a 360..
    im not saying a 258 is a bad motor.. for reliability it wins hands down.
    but with even a modest budget and a rebuild you will be happier with the V8
     
    FinoCJ likes this.
  4. Nov 28, 2018
    Daryl

    Daryl Sponsor Sponsor

    Bonney Lake, WA
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    Small block Chevy and never look back. Neither AMC motor is worth having in my experience.
     
    Dphillip, mike starck and tarry99 like this.
  5. Nov 28, 2018
    tarry99

    tarry99 Member Sponsor

    Northern California
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    Well If your already going to spend money on the rebuild of either AMC option................I must agree with Daryl.........Chevy V8 maybe V6 .....Unfettered power, reliability and support..........crate motors are out there along with any adaptors you need.....
     
  6. Nov 28, 2018
    Chilly

    Chilly Active Member

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    If it were mine I'd find a running 258 for cheap and slap it in. Another 232 should be free. Run it.

    The 232 was probably driving a T14, which wont take much abuse. Certainly not up to handling a 360 (you cant bore a 304 out to 360, by the way). Might last with a 304 if you dont horse it.

    There is a lot to be said for a SBC conversion. Inexpensive engine option, but you need to look at total cost. What transmission will you use? For sure NOT the T14. What xfer case? Adapters usually end up at $500 from engine to tranny, another $500 from tranny to xfer case. Are you able to tear into tranny and xfer case to change shafts if needed, or will you be farming that out? Will you need different length driveshafts? Probably. Have a MIG welder? Youll need new motor mounts and they probably wont line up to existing holes. The 232 radiator will be inadequate. SBC will need headers that either hug the block or run through fender wells. So need a new exhaust system. Throttle linkages, clutch linkages. Moving cross member.
     
  7. Nov 28, 2018
    rejeep

    rejeep Sponsor Sponsor

    Rochester, NY
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    yeah option (C) is prob the best sensible option, but when it comes to Jeeps and spending money sensible isn't always factored in..
     
    Everett Reed likes this.
  8. Nov 28, 2018
    Chilly

    Chilly Active Member

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    Rebuilding a 258 should hit you too hard if you farm out just the machining. Just dont try to do silly stuff like strokers and big cams. If the 258 isnt totally trashed just have it bored, new bearings (hopefully crank and rods measure up OK), gaskets.

    Disassemble the heads, check for sloppy valve to seal fit, burned valves, broken springs. Lap in the valves, put everything back where it came from. New valve stem seals, of course.

    Thats what Id do if I wanted to drive the Jeep. If you like working on them, or need it to have better long-term reliability then do something different I guess.
     
    Everett Reed likes this.
  9. Nov 28, 2018
    Chilly

    Chilly Active Member

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    A 4.0 EFI swap is another option. More work than rebuilding the 258, less work than a SBC.
     
  10. Nov 28, 2018
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    Nothing wrong with the 232. Has more cubic inches than the 225 V6 that everybody fawns over. Don't know if a good running 232 would be free, but if you have the '77 258 that has good compression and oil pressure, no reason not to use it.

    Doubtful. A healthy 304 is no match for a T-14 IMO. Members here have blown up the T-14 in a 225 Jeep. I expect you could bore out a 304 block to make a 360, but it would need sleeves to reinforce the cylinder walls. A 360 core would be much cheaper. And then you get the superior 360/401 heads too.

    The 304 stripped of all its emissions equipment will make a lot more power than a 258.

    I would not hesitate to drop in a 4.0L HO with its excellent Mopar/Bosch multiport fuel injection, but I think it's too much engine for a T-14.
     
  11. Nov 28, 2018
    Everett Reed

    Everett Reed New Member

    Southeast Missouri
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    Thanks to all that input your thoughts.

    After looking at the responses, it appears that unless I am going to be hotrodding the engine that there is no advantage in the 304 over the 258.

    I'm old enough now that I don't need to get every once of power out of everything I own. 110 horses is enough for the little 5 in my opinion and the torque curve is in about the right place.

    Small Block Chevy install is not something I would ever do. I don't mix breeds.
     
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  12. Nov 28, 2018
    Chilly

    Chilly Active Member

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    A preventive maintenance rebuild of the T14 might be a good idea while you have the engine out. Never be an easier time. If it shifts OK just pop in some new bearings and seals.
     
  13. Nov 28, 2018
    Everett Reed

    Everett Reed New Member

    Southeast Missouri
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    I agree. This is a frame off rebuild. I'm not building a museum correct/quality Jeep but it will be a complete rebuild from axles to interior as the old girl was just about beyond salvage. I will be tearing everything down to parade rest and stacking it back up as close to new condition as I can. I've got a couple of Jeeps to pull parts from. There is a '77 CJ7 and '73 CJ5 that are donors for this project.
     
  14. Nov 28, 2018
    homersdog

    homersdog Tulsa, Ok Sponsor

    Tulsa, OK
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    I am a little late to the discussion but if you just want a dependable Jeep the Rambler/AMC straight six was in production from 1964 to 2006 when ironically it was replaced by Chrysler 's 3.8 V6 in jeeps. The AMC straight 6 is extremely reliable, durable, smooth, torquey and there certainly no shortage of parts for them. You can get a fuel injected 4.0 (258) also. I am sometimes jealous of intermediate guys on here because they don't have to scrounge for parts as much as us Dauntless guys do.
     
  15. Nov 28, 2018
    sterlclan

    sterlclan Member Sponsor

    exploring the...
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    Yeah a six is fine,but nothing like a v8 rumble...
     
    Chilly likes this.
  16. Nov 29, 2018
    Chilly

    Chilly Active Member

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    Take your pick: rumble under the hood or jingle in your pocket. :D More holes to bore, more pistons to buy, fewer parts options, higher price. Not horribly expensive but a few hundred dollars more Id say.
     
  17. Nov 29, 2018
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    The '77, if a 3-speed, will have a T-150 transmission. This transmission is somewhat stronger than the Borg-Warner T-14 that came standard with a 232 in 1974. The T-150 is a Ford passenger car 3-speed built under license by Tremec for Jeep. It was the standard transmission for CJs 1976-1979; 232, 258 or 304. It will bolt up, but there will be small differences that you should be able to handle: slightly shorter overall length (OAL), different bell housing, different clutch parts... should be manageable though.
     
  18. Nov 29, 2018
    Everett Reed

    Everett Reed New Member

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    That's good to know. I'll try and get a look it and see if it is a manual. The '73 with the 304 has a locked up transmission in it.
     
  19. Nov 29, 2018
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
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    The '73 transmission will be a T-15, which is the strongest 3-speed Jeep offered in any platform. The T-15 was used as the standard transmission in V8 Wagoneers and J-10s and held up just fine. Worth saving for parts if it's not salvageable. It's a Borg-Warner transmission like the T-14, and the engine side will be identical to the T-14. The OAL is a little longer, but that would be the only external difference to the T-14.
     
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  20. Nov 29, 2018
    IrishCJ6

    IrishCJ6 Member

    Wicklow Ireland
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    I had a T150 behind my 360 for about 8 years, not sure on the abuse it had prior to me but I abused it until it finally spat the dummy. Now replaced with a T18
     

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