what cam for 340 bored 0.30 over?

Small Block Mopar Engine

  1. MOPAROFFICIAL

    MOPAROFFICIAL FABO Gold Member FABO Gold Member

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    Stock cam
     
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    • rumblefish360

      rumblefish360 So close, yet so far away FABO Gold Member

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      I can not advise on head killing since I don’t know what piston you have or where it sits in the cylinder.

      The stock 340 cam would do fine.
       
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      • SGlez10

        SGlez10 68 Barracuda

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        Fair enough. Here are some pictures to give you more context. This is all a work in progress so I’ll have more details as parts come in.
         
      • 1Badcolt

        1Badcolt Well-Known Member

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        Why not call [ Racer Brown ] get one made EXACTLY for what you have versus what someone has on the shelf etc !
        2pm to 7 pm Jim @ 410-866-7660
         
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        • AJ/FormS

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

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          Yur gonna have to more specific.
          And yur gonna have to make a decision on automatic OR stick, the optimum builds are different.
          And the "2.96" gears are the first thing that has to go.
          The reason being that a 5500 rpm shift rpm, will get you about 60 mph at the top of first. That sounds pretty good, but you got no passing gear. So when you pull out to pass somebody doing 58mph, on the downshift,your rpm will jump to 3560 in second , or to 6000 in first, neither of which is any good to pull from. On the other hand 65=2390@zero-slip, in Drive, so that's nice.
          a 5500 shift is about a 5100 rpm power peak which is about a 224@ .050 cam, which is like a 268advertized cam, like a 340 was born with..
          So you gotta decide if yur keepin' the 2.96s or not, cuz the engine build is gonna be completely different for about every 10 to 15% gear change.
          And the next thing to be assessed is the 2500 stall. If you put a 2500 on the 2.96 gears, yur gonna need a hi-torque 360 to get moving. After 20/25 mph it will be fine, but getting there will be frustrating.

          So if you are ready to throw out the 2.96s and the 2500, then the next question is this;.
          Hiway or city? a 340 with a TorqueFlite, can barely do both in the same combo, so you are gonna have to prioritize one or the other. So if hiway, spit out a number that you are willing to cruize no higher than. From that we can back-calculate a gear ratio, and a possible stall.
          Then we can start on the engine.

          If you build the engine first, without regard to these things, then you are setting yourself up for disappointment.

          And here's why;
          With a TF, no matter what street rear-gear you run, you will never get into third gear below the speed limit. For example; top of second even with 3.91s is about 5000@65mph. If you are cammed for that, that is the best she is gonna do. Very few guys run more than 3.91s on the street because in drive, 65 is 3160@zero-slip with 27" tires; could be 100 to 150 higher depending on the terrain.
          The point is; there is no good reason to run a 7000rpm engine in such a combo, cuz the only way to see 7000 is if the tires are spinning, or if yur speeding. Spinning ain't winning.
          Furthermore;
          A bigger cam always moves the operating rpm up; this is immutable, because of the way it is designed. If the heads support it, the higher rpm will make more horsepower. But generally, the cam will steal some of that rpm off the bottom. So the engine gets hi-rpm power by trading away lo-rpm power.
          Riddle me this; how is this a good thing for a streeter?
          It isn't.
          And so, to overcome that loss of low-rpm power, you have to install a higher rpm stall-speed TC, so your engine is never forced to pull in that dead-zone.
          OK so now you got both ends covered..... right?
          What about passing gear? At 58mph, as before, your kickdown-rpm into second will be about 4500, and 5000 will be 64mph and 5500 will be 71, so if you are OK with ripping past grandpa with the engine screaming, this might be ok, except for one thing; 71mph will be 3450@zero slip, probably closer to 3600 at WOT, relaxing to 3550 to cruise with. That is way to high for me to cruise at. Relaxing to 65 mph will get you about 3250.Still too much IMO for an A-body. It could take a few tricks to make this not tiring, on anything but short hops..

          So this sorta gets complcated.
          Way beyond a simple answer with only this to go on;

           
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          • Gator

            Gator Mopar or No Car

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            In my 340 .030 I am running a .509 purple cam with Hyd flat tappets, 3500 stall, 750 eddy, RPM air gap intake, 727 tranny with shift kit, MSD and I love the way my girl runs... I did no major changes when adding the cam, just a complete rebuild...12 yrs later still running strong.....
             
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            • AJ/FormS

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

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              What rear gear?
               
            • Gator

              Gator Mopar or No Car

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              Ford 9" 3.89 gear
               
            • QuickDart360

              QuickDart360 Well-Known Member

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              What rear gears with your 292 mopar cam? I run this cam with 3.91's and my dart sport does very well in street driving conditions. I love how my car runs with this stick. Many dislike it but I think its great!:thumbsup:
               
            • QuickDart360

              QuickDart360 Well-Known Member

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              Oh sorry didn't see next post where you give gearing my bad.
               
            • QuickDart360

              QuickDart360 Well-Known Member

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              Only difference is I run a Victor 340 intake rather than my previous airgap. I don't miss airgap at all!:)
               
            • rumblefish360

              rumblefish360 So close, yet so far away FABO Gold Member

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              Have you track tested it?
               
            • AJ/FormS

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

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              With a 360,a clutch, and an A833;
              The powerpeak on that 292, in my engine was up around 5500. Of course it smoked 245s right thru first gear, and hit 5500 at about 67mph at the top of second (3.55s). But she didn't stop pulling until later, much later. In fact, she still barked the tires shifting into third at over 80 mph.
              In those days, she was my DD, and I started out running 245/60-14s, and 55mph was ~2600, and the fuel economy was atrocious. I soon had 275/60-15s on there.
              Furthermore, with a clutch, and even with over 180psi cylinder pressure, the bottom end was a lil lazy. It really needed more than 3.55s, and I never liked the "Mustang-esque" take off; where you gotta rev it out to something like 3500 and sliiiiiip the clutch out.
              I only had that cam for a season, then sold it. 3.55s is all I wanted to run. It was a lotta fun for a while.
              The guy who bought it, put it into a 318 Satellite with 4.10s,and a 904, and went racing. Last I heard he was a happy guy.
              I'm not dissing the 292 cam.
              I'm saying it was not a good fit for me.
               
            • rumblefish360

              rumblefish360 So close, yet so far away FABO Gold Member

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              It’s a good bracket cam like the 95% of the rest of there line is. Once in the power band, it’s good, below it, not so much.
               
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              • QuickDart360

                QuickDart360 Well-Known Member

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                No just a fun street car. Don't plan any track just cruise and enjoy.
                 
              • rumblefish360

                rumblefish360 So close, yet so far away FABO Gold Member

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                Roger that one.
                 
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