Measuring cam lobes

Engine, Trans & Driveline

  1. Paul_G

    Paul_G Well-Known Member

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    The 383 is apart for a refresh. The cam is a Crane HMV 278-2, 222/234 @50, 467/494 lift, 114 LSA. I measured the cam lobes looking for variance, and I found it. The exhaust valves range from 1.591 to 1.598. The intakes range from 1.571 to 1.580, except one lobe that is 1.543. That is .030" smaller than the average. I am reluctant to re use this cam.
     
  2. zyzzyx

    zyzzyx FBBO Gold Member FBBO Gold Member

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    Yes, do not use it! Get a new one/new lifters
     
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    • kramer

      kramer Well-Known Member

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      Hey Paul how do you like that cam in the 383 how does it idle and what type of gears are you running behind it? The cam specs look pretty good for a nice streetable 383.
       
    • Cranky

      Cranky Banned Staff Member FBBO Gold Member

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      Look at the old lifters and see what the wear looks like. That will tell you even more....
       
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      • Paul_G

        Paul_G Well-Known Member

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        The lifter on that lobe is flat.
         
        Last edited: Nov 22, 2020 at 5:28 PM
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        • Paul_G

          Paul_G Well-Known Member

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          Very happy with how the engine performed with good plugs. Idle was smooth at 850 RPM, just a little cammy. 3.23 gears, with a 4 speed. Good mid range torque. Engine was getting tired, fouling plugs and smoking. Hence the rebuild.

          Looking on Summits website they have a similar cam to that one.
          https://www.summitracing.com/parts/sum-6401

          Duration at 050 inch Lift:224 int./234 exh.
          Valve Lift with Factory Rocker Arm Ratio:0.466 int./0.488 exh.
          Lobe Separation (degrees):114
           
        • 4mulas

          4mulas Well-Known Member

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          Is this a new cam or old? Also, I think you should measure the base circle in each one then the cam lift, multiple by the rocker ratio before thinking one may be too worn out. Perhaps the lobe that is lower than rest has/was made with a smaller base circle too
           
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          • Nate S

            Nate S Well-Known Member

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            Measure not only the peak but the base circle. It’s the difference you care about not the overall. These numbers may be fine if the base circle is proportionally smaller when the overall is smaller. Best bet is throw it in a block and indicate it. It may in fact be junk, but it may be fine too.
             
          • Paul_G

            Paul_G Well-Known Member

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            That is what I will do when I get the block back.
             
          • khryslerkid

            khryslerkid FBBO Gold Member FBBO Gold Member

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            That's the cam I'm using in my 440. I'm getting by with the stock converter and 3.23 gears. It's a single bolt cam. It does require a heavier spring than stock. I cut the valve guides down a little for retainer clearance. I didn't use the 911 springs they recommend, they're too heavy. I went a smidge lighter. It's all in "My Photo Garage". I like it :)



             
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