any benefit to swapping heads?

Discussion in 'Small Block Mopar Engine' started by djais1801, Jul 31, 2018.

  1. djais1801

    djais1801 FABO Gold Member FABO Gold Member

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    I am not knowledgable mechanically so forgive me in advance. I have a 72 demon with a 340 block 69 and 360 heads with a purple cam 282/482. The 360 heads are 1.88 intake 1.62 exhaust.
    I have a complete set of X heads with 2.02 intake and 1.60 exhaust...
    this is a 4spd street car with a weiand dual plane intake and 2.25 stock exhaust manifolds. 355 rear sure grip.

    Will I have any noticeable power/torque swapping the heads?
     
    Last edited: Jul 31, 2018
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    • brian6pac

      brian6pac Well-Known Member

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      Probably looking at 25 - 30 HP boost just doing the swap, I'm sure some people will disagree but you will feel the difference for sure. What cam do you have ?
       
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      • djais1801

        djais1801 FABO Gold Member FABO Gold Member

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        Purple shaft 282/482 I believe-it was in there when I bought it
         
      • yellow rose

        yellow rose Doctor of Thinkology.

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        I LOVE that car!

        If it was mine, I probably wouldn't do the head swap unless you think the heads on the car need a valve job or needs guides or something

        I LOVE THAT CAR!!!!
         
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        • djais1801

          djais1801 FABO Gold Member FABO Gold Member

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          Thanks for the compliment...you don’t see white demons everyday which is what got me❤️❤️
           
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          • brian6pac

            brian6pac Well-Known Member

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            Yea I got to say that thing sounds sweet, really nice ride,
             
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            • djais1801

              djais1801 FABO Gold Member FABO Gold Member

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              For 25hp the juice is worth the squeeze
               
            • Treblig

              Treblig FABO Gold Member FABO Gold Member

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              As long as it sounds as good after as it does right now!!!!:steering:
               
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              • flyfish

                flyfish C8H18+N2O = :-D

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                I would not bother swapping heads unless it is a ported aftermarket head (that is a lot of work for 20 ish hp, and stock heads don't flow for crap). There are easier ways to grab another 20-25hp.
                 
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                • brian6pac

                  brian6pac Well-Known Member

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                  It's just a few bolts, It's not that hard
                   
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                  • toolmanmike

                    toolmanmike FABO Staff Staff Member FABO Gold Member

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                    Nice! It's up to you but I wouldn't worry about 20 horse. It is perfect the way it is.
                     
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                    • mderoy340

                      mderoy340 Well-Known Member

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                      I'd leave it as is and enjoy what you have. With stock exhaust the gain will be small. Nice ride!
                       
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                      • Frnknsteen

                        Frnknsteen FABO Gold Member FABO Gold Member

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                        I just had a chance to listen to your video and I have to agree. It sounds great! I agree with above that with stock porting, and stock manifolds you probably won't notice enough gain to be worth the effort.

                        You say it has "2.25 stock exhaust manifolds". Are you saying you are running 2 1/4" exhaust with stock manifolds? What mufflers are you running? Any drone at any particular RPM? I'm curious because I am running 2 1/4" pipes, and I'm not really sold on the sound of the Magnaflow mufflers I put on, but there's no drone. My car had Flowmasters dumping in front of the rear axle, but there was a HORRIBLE drone about 1200-1500 RPM, so I'm nervous to go back to Flowmaster mufflers.
                         
                      • 72bluNblu

                        72bluNblu FABO Gold Member FABO Gold Member

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                        The only difference between those two sets of heads is the size of the intake valve. The ports and chambers are the same size (at least they're supposed to be), if you put 2.02's in the 360 heads they'd flow exactly the same as the X's. Swapping the 360 heads for the X's wouldn't buy you much at all with regard to cfm flow. If you had some port work done on the X heads it might be a different story, but your engine set up isn't super aggressive to take advantage of a lot of extra head flow anyway.

                        You can look at some flow numbers here, some of the 1.88/1.60 heads are shown as flowing just as much or more than some of the 2.02/1.60 heads. I would expect most of the time the 2.02/1.60 heads would flow a little better, but given the factory tolerances that's not always the case. It's no massive improvement anyway.

                        Cylinder Heads Flow Data at 28" H2O

                        I doubt you'd notice any "seat of the pants" difference at all. And of course you run the risk of changing the compression ratio for the worse, stock head chamber volume was anywhere from 65 cc's up to 72cc's. The X's weren't any better than the 360's for chamber volume, and there's always a chance you have a set of 360 heads that are on the smaller chamber side and a set of X's on the large side. So you could actually lose compression ratio. Now, more than likely they're pretty close to the same size and any difference would be minor, but you never know. I have a set of later 308 heads that have 65cc chambers.
                         
                      • perfacar

                        perfacar Well-Known Member

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                        for your information, the 1.88 does have more port velocity = more air in engine. we've tested both heads, the 1.88 will stay with a 2.02. port velocity is what you need.
                         
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                        • brian6pac

                          brian6pac Well-Known Member

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                          If you put a set of X heads on advance the cam 4*, new chain if it needs it, you need to degree it and see where it is but I believe 108* ATDC is spec for that cam, you will have a bigger power gain than you think.
                           
                        • stroked340

                          stroked340 Well-Known Member

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                          WOW..nice car I wouldn't bother with the head swap but when you do upgrade change that cam..MUCH better ones on the market now..
                           
                        • rumblefish360

                          rumblefish360 so close yet so far away

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                          Flawed data table, disgraced machinists (bullshiters and hacks) additions were let in. The tables are to wide and varied.

                          A stock head w/1.88 will pick up flow with a larger valve and no other work added or done. It’s been shown and proven for deacades.

                          To the OP;

                          However, FWIW, I wouldn’t do the swap unless the next set of heads were 2.02/1.60 & bowl ported and relieved in the pushrod pinch area (made wider) with headers. Your leaving a hell of a lot of power on the table!
                           
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                          • Gamedog

                            Gamedog Well-Known Member

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                            Dammit she sounds good.

                            As to your question, nope heads don't do anything. Do yourself a favor and go ahead ship those X heads to me I'll PM you my address.

                            :p
                             
                          • Wyrmrider

                            Wyrmrider Well-Known Member

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                            OK
                            High compression or low compression 340
                            If High and you have marginal gears you can do it but you can also get a flat spot or bog which is no fun till the rev's come up then you get the 20 hp at the top end
                            Low compression 340 do not even think about it - velocity in both cases you have to get the velocity up with the bigger valves which means flow at a higher rpm
                            x2 on the amount of gain with stock exhaust- which is the bottleneck in SBM stock heads
                             
                          • brian6pac

                            brian6pac Well-Known Member

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                            Never seen anyone put in smaller valves to make more power!
                             
                          • Wyrmrider

                            Wyrmrider Well-Known Member

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                            I'm not talking about making more top end power
                            I'm talking about taking off up hill from a light with a 4 speed and 3:55 gears
                            I want to be able to let the clutch out and drive off
                            no high rpm starts or clutch slipping
                            and I definitely do not want a bog after letting the clutch out or a bog when I step on the gas cruzing in 4th
                            been there- done that
                            big difference between a low compression and high compression build for what you can get away with
                             
                          • rumblefish360

                            rumblefish360 so close yet so far away

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                            Your the only one talking about compression, transmission & gears while the OP is asking about 1.88 vs 2.02 heads. I’ll assumed there chambers are within 2cc of each other and not the wild NHRA listed swings in cc’s.

                            Simple question in, simple answer out.

                            Why you and AJ make mountains out of mole hills is beyond me.
                             
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                            • Demonic

                              Demonic Well-Known Member

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                              ^ This. You have good heads, ready for a little work. Add in new valve job, guide check, avoid the factory ski jump valves, a light cut to true them and a thin head gasket. You'll be happy.
                               
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                              • Wyrmrider

                                Wyrmrider Well-Known Member

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                                not mountains out of moleholes
                                you do not want the dreaded BOSS 302 syndrome in your mopar
                                you want instant response and torque when you hit the gas
                                the 10 hp he would gain up top without headers is not worth it
                                really want to wake it up take those 2.02 valves and put some 30 degree seats on them and cut them down to 1.94-`1.96 (whatever it takes to get some margin)
                                then figure out the difference in curtain areas