whats better J or X heads

Mopar General Discussions

  1. dazedand confused

    dazedand confused Well-Known Member

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    So is there a difference between the J heads and the X heads for a low buget performance build ??? I have a pair of J heads with 2.02 valves .
     
  2. yellow rose

    yellow rose Overnight Sensation

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    Nope. Not a pinch of crap difference.
     
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    • dazedand confused

      dazedand confused Well-Known Member

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      its amazing how people are trying to get crazy prices for X heads? Im starting on a low buget 360 build
       
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      • Treblig

        Treblig Well-Known Member

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        I've heard of a "pinch of salt"....never heard of a pinch of crap, who would do that???:rofl:
         
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        • dazedand confused

          dazedand confused Well-Known Member

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          lol
           
        • 318willrun

          318willrun Utube channel 318willrun

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          It comes from him dealing with J par for 4 years... :D :D :D
           
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          • 318willrun

            318willrun Utube channel 318willrun

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            a lot of it is restoration money :)
             
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            • 66fs

              66fs FABO Gold Member FABO Gold Member

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              Untouched, X heads are better, by a small margin. Both are good. Ported is how good the porter is.
               
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              • ir3333

                ir3333 Well-Known Member

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                it may make a difference value wise for a '70 or earlier restoration.They will all support about 400 hp ..even the small 1.88 intake valve j heads and can be had quite cheap sometimes. Get
                an economical valve job you can put together a nice street engine without much expense...and they
                look so much nicer on a stock style muscle car.
                 
              • QuickDart360

                QuickDart360 Well-Known Member

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                I've seen a flow chart that shows the X head to outflow the J head and other factory heads. So X takes the win.
                 
              • abodyjoe

                abodyjoe Well-Known Member

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                Did both sets have the same valve size? Some j's Had the same large valves as the X heads. Others used smaller Valves.
                 
              • QuickDart360

                QuickDart360 Well-Known Member

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                Yes it was comparing the 2.02 valved j head and the x head. The j head with 1.88's fared even lower.
                 
              • SGBARRACUDA

                SGBARRACUDA ROY FABO Gold Member

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                I would like to see a bonified flow test that shows a X head in original form that out flows a 2.02 J head?
                 
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                • 318willrun

                  318willrun Utube channel 318willrun

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                  basically same head. I doubt there would be an advantage if both had 2.02
                   
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                  • toolmanmike

                    toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                    All X heads had 2.02 intakes. J heads had 1.88 or 2 02's.
                     
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                    • abodyjoe

                      abodyjoe Well-Known Member

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                      That's what I was saying.
                       
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                      • A56

                        A56 MoParAffliction FABO Gold Member

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                        :thumbsup:
                        even less value than salt?????
                         
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                        • toolmanmike

                          toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                          Let's put it this way, I have heard of X and J heads on the same engine. There can't be that much difference in flow between the two.
                           
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                          • 66jim

                            66jim Well-Known Member

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                            My belief is the X is more $$ because:
                            The letter X itself id more "exotic" than the letter J...LOL
                            X came on pre emission 340's which carried a "pettigree" no mutts allowed
                            Mopar hoarders have squirreled them for so long they have become Folklore.
                            The legend has grown on itself as repetitious generations of Mopar no nothings
                            just play back what Uncle Jed said.
                            Go ahead and pay more for the golden X it doesn't matter how many tests have proven same as J ...Uncle Jed said.....
                             
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                            • toolmanmike

                              toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                              And how about the Z or O heads. They were the same as the J heads. But the U and some O heads were the 340 TA heads. Just a designation letter.
                               
                            • 318willrun

                              318willrun Utube channel 318willrun

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                              put a 2.02 X head on one bank, and a 302 head on the other bank.. that way you have the low end torque covered and the 6k rpm range covered. Talk about street and strip.... :D
                               
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                              • toolmanmike

                                toolmanmike FABO MODERATOR Staff Member FABO Gold Member

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                                :rofl::rofl::rofl:
                                Don't say that. Someone will believe it.
                                 
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                                • MOPAROFFICIAL

                                  MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                                  Check the port volume.
                                  They're are differences.
                                  Floors are different from each other. Took years to notice it.
                                   
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                                  • dazedand confused

                                    dazedand confused Well-Known Member

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                                    Did not know that on the dimensions on the X heads . Ok well ill have to stick with these J heads since i bought them for $200. For the set with the 2.02 valves. Im going to have them milled down . I will be gasket matching the ports intake and exhaust . The valves will be cut back for flow and polished. Bowels cleaned up.
                                     
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                                    • Jadaharabi

                                      Jadaharabi FABO Gold Member FABO Gold Member

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                                      If a J head flows 250 cfm @ 400 lift.
                                      and an X head flows 250 @ 400 lift.

                                      Would it matter what letter is on the head?
                                       
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