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  • 4.0 head on 258

    Looking for info on what is the best year (if one) for the 4.0 head conversion on the 258. Any experience with Clifford intake, exhaust and 40IDF carbs along with a DUI performance Dist. HEI system?

  • #2
    The 4.0 head came on 1991 and newer Jeeps. Any head will do. You will also need to grab the valve cover and exhaust manifold off of the donor vehicle. If you can, get the stuff off of a Cherokee. The manifold is supposed to be stronger. Mine came off of a ’91 Cherokee. I’m not familiar with the Clifford products. I’m using the stock intake with a 38/38 Weber that does great. I am running an HEI out of a ’78 Chevy straight 6. The head was a big improvement. It also added low end torque also. Something I was not expecting. The HEI put a stop to all pinging. I now run this engine on 87 octane gas with the timing set at 6 degrees BTDC. I also have a small Comp Cam in this engine. Part number X4250H I put the smaller cam in because I didn’t want to lose low end torque, but now, after the head change, I wish I had gone larger. Hope this helps.


    • #3
      4.0 head on 258

      Thanks for the reply. I guess I'm off to the junkyard. Clifford Performance suggested to 40IDF card with upgrades. Any one have any pros or cons with this carb. What about headers and exhaust?