Please Help Me Decipher My Cam Specs Sheet

Small Block Mopar Engine

  1. AJ/FormS

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

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    I've been preaching something like that for years, except straddling the power peak and that's why I rebdachit out of my combo. And maybe why it goes 93 in the 1/8th. IDK, I just like the sweet sound of 8 little KB107s flailing about in brotherhood with screaming pipes, at 7000. I could care less if it might go quicker or faster,shifting earlier; I ain't pulling the stick 'til I get my fix!,lol.
    That's also why I don't do automatics, the TFsplits (.59-.69) are quite wide, and it's easy to fall off the cam. If you don't have the TM or pressure, there you are waiting for something to happen. The 2-3 ain't so bad, but the engine still needs a heck of a powerband; about 2000rpm. My combo is only 1250/1350ish. I'm thinking of getting something like a 282/288/100 tight-lash solid next go-round... hyup ~195psi/~181VP and Caltracks should do it.
    Quick; how fast will it go,lol. I don't care,obviously, 181VP is only good for one thing; showing off. I mean that's supercharged 408 territory.
     
  2. nm9stheham

    nm9stheham Well-Known Member

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    Similar thinking..... I think of straddling the torque peak because:
    • Torque is what accelerates the car, regardless of the HP numbers; keeping the torque numbers as high as you can over time is the goal
    • Straddling the HP peak means that the torque to the wheels will fall off at the upper end of the operating RPM range, versus what it could be operating lower down
    I'm pretty sure that the HP curve, as it changes quickly over time, produces a misleading view in terms of energy put into the car. The HP curve of the engine is partly do to RPM changes, not real energy put into the car. (But I gotta think about this more....)
     
  3. Mattax

    Mattax Just the facts, ma'am FABO Gold Member

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    I think you've got that concept right. Its one way to make power is with a higher revving engine.
    Power is energy over time. So its related but not the same, so that part you've got partly rightly depending on how you want to at it.
     
  4. MOPAROFFICIAL

    MOPAROFFICIAL Well-Known Member

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    "Mildly ported" by the right person will give you the 245-250cfm you need to make those dyno number. Respectable power given that.

    Now if they were 180+cc intake runners, can be done no problem, they wouldn't choke the rpm.

    I rev mine 6800 or so with j heads@186cc port and 280 cfm .

    I edited, only here do words disappear from my posts and lead to the opposite of what I'm saying.
     
    Last edited: Oct 17, 2018
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    • forphorty

      forphorty Well-Known Member

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      A high stall torque converter can help shift recovery quite a bit, therefore not as easy to "fall off the cam". With the 9.5 Dynamic converter in my 440 car, the RPM at WOT never drops below about 4500 regardless of the shift point.
       
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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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        I don't have a TC, so can't take advantage of that feature ,but I know what you mean
         
      • nm9stheham

        nm9stheham Well-Known Member

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        Which is pretty much what the clutch packs in top-fuelers do anymore. If you listen to them on a run, the RPM's stay pretty constant after launching..... keeping the engine RPM's around the torque peak.

        Here is an interesting article related to that. It can get confusing as they go back and forth between torque and HP, but makes the point the peak acceleration occurs when the engine RPM's settle in around peak torque. There is a lot of discussion of HP in relation to budgeting the energy distribution between different energy losses (which is the way to do that computation since a lot of those losses are most easily worked with as HP) and what gets left to accelerate the 'car'.
        FORGET 8,000 HORSEPOWER ... TOP FUEL IS NOW OVER 10,000 HORSEPOWER! [National Dragster]
         
      • Wyrmrider

        Wyrmrider Well-Known Member

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        Back when running sports cars we straddled the hp curve
        you want it pulling as good or better after the shift
        but not drop off a cliff if you are are stuck in traffic and have to corner a few hundred rpm lower that you would like and not want to downshift- you still want it to pull
         
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        • MobileCustoms

          MobileCustoms Well-Known Member

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          Well, low and behold, I was reorganizing all the 'stuff' in my car's trunk and found the actual cam card. LOL...
          Thanks again for the previous input and thoughts. I have a new converter on order from PTC
          Here's the cam card:
          Cam Card - Specs.jpg
           
        • nm9stheham

          nm9stheham Well-Known Member

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          Curious.... what stall speed is the new TC coming with? That is a darned hefty cam.
           
        • B3RE

          B3RE B³ Racing Engines

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          While the lobe acc rates are going to have an effect on rpm capability, you should be revving higher than that with a cam of that size. With what I know about roller rocker geometry, if you did nothing but bolt the rockers to the stands, the geometry is not right and will cause more valvetrain instability. That will further hurt rpm potential, and kill parts in a hurry. Do a search for rocker geometry here, and you will find a bunch of information, as well as links to tech articles, that will be very helpful.
           
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          • MobileCustoms

            MobileCustoms Well-Known Member

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            That makes sense, thanks. I will look into that.
             
          • MobileCustoms

            MobileCustoms Well-Known Member

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            3200-3400 is what they suggested
             
          • nm9stheham

            nm9stheham Well-Known Member

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            Makes good sense; tnx.
             
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            • MobileCustoms

              MobileCustoms Well-Known Member

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              @B3RE , Thanks again for the insight. I think you may be correct but I'd like to chat briefly if that's OK...
               
            • B3RE

              B3RE B³ Racing Engines

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              Sure, I'll be around until 5pm edst. 717-497-6572
               
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              • MobileCustoms

                MobileCustoms Well-Known Member

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                Thanks, Mike! I read your Tech Series articles on Rocker Arm Geometry... really great info and well-explained! I sent you an email and will be giving you a call shortly!
                -Doug
                 
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                • MobileCustoms

                  MobileCustoms Well-Known Member

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                  UPDATE:
                  I will probably start a fresh thread for this rocker geometry correction but wanted to follow up here first. I contacted Mike @B3RE Racing Engines and he hooked me up with a custom geometry correction kit. What a great guy to deal with! I'll be putting my engine on the dyno again next Friday, the 28th and will post up the new results afterwards.
                  Here's a photo of the roller sweep on the valve tips, before and after the kit. I'd say this is a huge improvement.

                  Rocker Geometry - FIXED.jpg
                  Rocker Geometry Kit.jpg
                   
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                  • stixx

                    stixx FABO Gold Member FABO Gold Member

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                    Smokin...!
                     
                  • RustyRatRod

                    RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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                    Yes, them other two cats are blind.
                     
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