1. #1
    scjeepguy's Avatar
    scjeepguy is offline Junior Member
    Join Date
    Apr 2008

    replacing 4.2L 6 with a 304 V8


    I am in need of a little help and advice. I bought a 84 CJ7 with a 4.2L 6 in it and the motor needs replacing or rebuilding. I found a 304 that I bought at a good deal and I am planning on switching them out. The current transmission is a the T5 5 speed. I was wondering if anyone has any experience with this type of swap and if I will need to do any modifications to make this work. My friend thinks that the swap should be just a simple switch but I wanted to make sure. Any help would be greatly appreciated.



  2. #2
    Bounty__Hunter's Avatar
    Bounty__Hunter is offline Moderator
    Join Date
    Nov 2002
    Southern Illinois

    Re: replacing 4.2L 6 with a 304 V8

    I think it'll bolt in with CJ v8 motor mounts.

  3. #3
    lah2420's Avatar
    lah2420 is offline Senior Member
    Join Date
    Mar 2004

    Re: replacing 4.2L 6 with a 304 V8

    A friend of mine went through that a couple of years ago. I can't remember all the details, but here's what I remember. First he had fits with the wiring harness. Some of the wiring had to be lengthened because it was on the wrong side. Also, some of it that went to the side of the 4.2 had to go to the top or front of the 304. He used his T5 and after fixing the transmission twice, is now looking for an automatic. He also twisted the rear axle tubes. It seems that the 304 was so fond of spinning the tires that he would allow it to do so any time it wanted to. The tubes let go on him. I don't know how much of the trouble was due to the motor and how much was due to him though.

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