just one more cam selection thread

Small Block Mopar Engine

  1. QuickDart360

    QuickDart360 Well-Known Member

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    Ahh the old 292/508 mopar purple stick!!:thumbsup: would need to be advanced quite a bit but will give an idle note like no other cam!!:D
     
  2. roccodart440

    roccodart440 Well-Known Member

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    Well, I had my heads done by IQ52 as well as the intake and custom roller. That cam has a split duration and I wasn't going to argue with him.

    Now there may have been a reason for it, such as a proportionally small exhaust valve or he thought it needed a bigger header than I run. Point being, I'm sure there was a good reason and it surely isn't going to hurt anything.
     
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    • yellow rose

      yellow rose Overnight Sensation

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      What heads? Usually they split the duration and open the LSA to make RPM after peak last longer but they give up a ton in the gear change.

      I very rarely ever want to see a split unless it's on alcohol.
       
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      • Wyrmrider

        Wyrmrider Well-Known Member

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        Just another reason I do not like "one size fits all" cams
        you notice how late motors with better exhaust may even use exhaust shorter duration than intakes
        best to use head flows to pick durations along with all the rest of needed inputs
        rule of thumb is early stock exhaust ports with stock manifolds and restrictive exhaust needs more duration- but even then not as much as some popular catalog grinds
        late heads and headers do not need much duration difference but still need a different lobe
        Best to calculate each lobe individually
        the intake lobe has to match piston demand - which is none at TDC that's header pull-the intake is contoured to the demand- which is also stroke/ rod length related
        whereas the exhaust is opening under pressure and wants to open quickly to bled down pressure - but not too early to lose expansion/ power/ mileage
        Intake closes as piston is coming up and closing tries to keep intake gas flowing as long as possible without reversion
        obviously full power rpm intake close curve is different than driving down the street mostly hardly any throttle opening
         
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        • AJ/FormS

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

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          Just to expand on that a lil;
          In my experience; there is a night and day difference between a Hughes HE2330AL and a Hughes HE3037AL.
          For the smaller cam, the numbers are;
          270/276/110+4/53 overlap/119 compression/108 extraction.
          With this cam I was able to gear the engine down to 65mph =1600,( with double overdrive; A833od plus GVod)and the car returned phenomenal fuel mileage. Some would say impossible numbers.
          The larger one is;
          276/286/110+4/61 overlap/116 compression/103 extraction.
          This cam would not pull the numbers. I figured the problem was the headers pulling raw fuel past the open valves during overlap, at the 1600 rpm. So I bumped the stick back one gear and 65=2240, and voila I'm on the right track. Cruise vacuum is up, and so is the fuel mileage.
          To cover the loss of 119less 116 degrees of compression, I milled the decks to equalize the cylinder pressure, no problem there.
          But the 108 less 103=5 degrees less extraction cannot be overcome so easily. And because of this, and I guess the 61 versus 54 degrees overlap, fuel mileage has dropped to 50%. Well, I changed to 295 tires from 275s at about the same time, so that mightof also contributed to the problem.. All in all I was very sad when that smaller cam dropped lobes.
          But the point is this; IMO, there exists, in my combo at least, a switch point between these two cams, and I'm gonna go out on a limb and say it's probably in the split pattern, and my engine liked it. Heckya it makes waaay more power, with the larger cam. But I really miss the fuel-mileage.
          I already have ideas for my next cam,lol.It will be a solid FT.
           
          Last edited: Sep 6, 2019
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          • roccodart440

            roccodart440 Well-Known Member

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            Fully ported (345cfm ip) 2.20 valved eddy rpms with custom solid roller from comp. I forget the exact specs but 250 something duration at .050, .650ish lift and 112LSA.
             
          • yellow rose

            yellow rose Overnight Sensation

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            Crap. I was thinking small block. Makes more sense now.
             
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            • JoePole1

              JoePole1 A dude in a B body FABO Gold Member

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              Reviving. Hey Scott.....Any feedback on your cam/lifter/spring choice?
               
            • scott657

              scott657 Well-Known Member

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              Haven’t even gotten to it yet
              I have chosen a Lunati 701 cam
              For when I get to it. Seemed to be a good consensus for that cam in about a 9 to 1 engine
              Plus or more likely minus a couple of points
              The
               
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              • Wyrmrider

                Wyrmrider Well-Known Member

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                keep posting post cranking comp when you get it together and mech comp
                 
              • scott657

                scott657 Well-Known Member

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                I will.
                 
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