383 magnum versus 383 big block

Magnum Engine Swaps

  1. dukeboy_318

    dukeboy_318 Our Lives, Our Fortunes and Our Sacred Honor. FABO Gold Member

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    on my desktop dyno, they have an option for "aluminum aftermarket head" select it, and the flow numbers are close to the eddy heads he mentioned. You can adjust based off the advertised flow from eddy if you want.
     
  2. toolmanmike

    toolmanmike FABO Staff Staff Member FABO Gold Member

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    I have Desktop Dyno 5. I don't see that option.
     
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    • dukeboy_318

      dukeboy_318 Our Lives, Our Fortunes and Our Sacred Honor. FABO Gold Member

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      hmmm thats just a newer version of mine, I'm on 3. is there a little valve looking button thing near the drop down menu for the heads?
       
    • toolmanmike

      toolmanmike FABO Staff Staff Member FABO Gold Member

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      Nope

      Capture.PNG
       
    • dukeboy_318

      dukeboy_318 Our Lives, Our Fortunes and Our Sacred Honor. FABO Gold Member

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      Hmmm I’ll run it later when I get on my laptop. I doubt it makes a huge difference
       
    • AJ/FormS

      AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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      As for the trans you can bolt that onto any SBM
      As for roller lifters, that is a benefit.
      As for a roller cam, at your stated useage, I doubt the Magnum is much if any advantage. The clearance ramps on hydraulic roller cams are very long and very slow... sometimes nearly three cam sizes greater from advertised to .050,never mind to fully closed.This allows a lot of cylinder pressure at low rpm, to escape back up into the intake. And for a streeter, the vast majority of it's time is spent where? Riiight, at low rpm. And that blows the efficiency angle right outta the water. So, IMO you'd be better off with a fast-rate FTH cam and best would be a solid lifter, narrower than 112 LSA. The point being; In this case I see very little advantage to a Magnum.
      Also;it is impossible to build a 318 to 383 with a 4 " stroke;even at 3.91 bore, it comes to 384.25. And can you even find a Magnum with round bores at 3.91 bore? IDK .....
      By the time you clean up the cylinders to round and straight, at .020, the cubes have climbed to 388. You'll be in the same pickle as the later 396 Chevelles.... which were actually 402s , as if it made a difference,lol.
       
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      • qkcuda

        qkcuda Well-Known Member

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        To answer a few questions I had $1,000 and a lot of time invested in my ported 452's so I would probably do a budget aftermarket head on either build. I have a 500 stroker in the cuda so I am not shy about using a big block. To be honest I have been thinking about more of a cruiser than a race car lately. Something I could drive 8 hours to Carlisle. One of my dream cars is a 66 or 67 Charger. The 383 thing is to be able to run the 383 four barrel badges (I know that is my warped mind). I realize that as soon as you bore either engine they are bigger than that. Thanks for all your responses.
         
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        • qkcuda

          qkcuda Well-Known Member

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          Also I run a hydraulic roller in the 500 now. I've had it with flat tappet cams after one ruined my 400. What cam would you use in the magnum stroker?
           
        • toolmanmike

          toolmanmike FABO Staff Staff Member FABO Gold Member

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          Best thing to do is talk to the cam grinder. Way too many choices to choose from here.
           
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          • dukeboy_318

            dukeboy_318 Our Lives, Our Fortunes and Our Sacred Honor. FABO Gold Member

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            Oregon cam grinders.
             
          • toolmanmike

            toolmanmike FABO Staff Staff Member FABO Gold Member

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            I went back in and changed the valve sizes. That made a difference. The 383 comes out on top now. It's still a very inaccurate comparison on my part.
             
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            • dukeboy_318

              dukeboy_318 Our Lives, Our Fortunes and Our Sacred Honor. FABO Gold Member

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              Whats a roller cam do in that big block 383?
               
            • toolmanmike

              toolmanmike FABO Staff Staff Member FABO Gold Member

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              That could take all week to compare. Lol Too many choices.
               
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              • 66jim

                66jim Well-Known Member

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                383 B motors are extremely rugged, stroked 318?
                 
              • toolmanmike

                toolmanmike FABO Staff Staff Member FABO Gold Member

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                Yep. A tough comparison really. Similar cubic inches but that's it.
                 
              • dukeboy_318

                dukeboy_318 Our Lives, Our Fortunes and Our Sacred Honor. FABO Gold Member

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                say a similar one that one would run in the stroked 318?
                 
              • MRGTX

                MRGTX Well-Known Member

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                Are these calculations taking into account the better exhaust path that's possible with the small block? Last I knew, those manifolds or headers on the big block A body cars will be compromised to clear the steering, torsion bars, etc.

                This is the very first thing that came to my mind...if the difference is only 75lbs, it's not as big of a deal as I was thinking but this is significant...worth almost a tenth in the quarter mile.

                I realize that the OP mentioned that this was already a heavy car (running AC to boot) but weight and weight distribution are significant factors in how the car is going to drive.

                I love big blocks as much as the next guy but I'd lean toward saving some trouble and sticking with the small block. Add in aluminum manifold, heads, water pump, some light pullies, electric fans, and you'd be way lighter than an iron head big block and you would be on your way to a better driving experience, IMO.
                 
              • Willyrd

                Willyrd Well-Known Member

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                Yeah those are little baby valves for the displacement
                 
              • Willyrd

                Willyrd Well-Known Member

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                If you wanna go off the shelf I'd do like 108 lsa for that hot boy chop and 7000 degrees of duration and 3 inches of lift. Just messin with ya. Definitely keep the duration up and the lsa down though
                 
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