How To Pick Your Camshaft 101

Mopar Racers Forum

How Do You Pick Your Cam?

  1. I let my builder pick whatever he/she says I should

    8 vote(s)
    17.4%
  2. I copy someone’s build

    3 vote(s)
    6.5%
  3. I use various methods from research/experience

    28 vote(s)
    60.9%
  4. The one at the bottom of the catalog page

    1 vote(s)
    2.2%
  5. I read all the guru posts and am too confused, I’m selling the damn car!

    2 vote(s)
    4.3%
  6. Most lumpy rumpity rumpity they got!

    4 vote(s)
    8.7%
  1. 12many

    12many Well-Known Member

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    Yes, all the confusion with encyclopedic novels, numbers and calculations, the terms, durations, area under the curve, lifter diameter, Chevy lobes, Mopar lobes etc is all just hogwash! This site and the sound clips are all you need. Pick the sound you like best and buy that cam! :lol:Camshaft Sounds | Library of Camshaft Sounds
     
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    • yellow rose

      yellow rose Doctor of Thinkology.

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      I have a general idea of what I *THINK* I want or need as far as what the head flows, the CR, header size, gear ratio, transmission type and ratios, clutch or converter and some other stuff.

      Then it's the cam grinders job to either say yup, you're on it, or he tells me I'm completely off the reservation and smoking hippie lettuce.

      The last cam I bought I new I wanted to net .600 lift (that's about all the lift you can get on production rocker gear) and I was 100% sure I wasn't going to accept a split pattern cam that reduced intake duration, added exhaust timing and blows the LSA out to make the shift RPM the same as the correct cam. That I want having. That's stupid. Especially with a stick car. Three times you drop down to the torque peak (you should be anyway) and have to pull that back. Reducing intake area and adding exhaust area and opening up the LSA is a mid range killer. For all the whining I hear about bottom and mid range power, and yet they let cam grinders convince them that that method is the way to go. It's stupid if you want an engine that spends most of its time in the middle. Why give that up? Because most guys don't want to learn to tune a carb. Most guys take the easy way. And most cheap EFI systems don't like a cam with "tight" LSA's so they get compromised on cam timing.

      It takes a lot to convince me I'm overboard on what I want. I can be moved a bit here and there, but I've been doing this since the 1980's and I've seen all this dual pattern, 4 pattern, wide LSA's and that type of garbage.

      If you have production based cylinder head architecture and you are running more that a 108 LSA I'd bet everything I have and some stuff I don't you are leaving power and driveability on the table.

      My very BEST W2 and W5 stuff, my BEST stuff with 55 degree seats on the W5 heads and more work into them than a reasonable man would do, all that, and the widest LSA I ever ran was 109 and I though that was two degrees too wide. I'd have given up a bit at 8800 to get a touch more in the gear change.

      Just my .02 from years of breaking crap and fixing junk.
       
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      • skep419

        skep419 It's only money, you can always make more

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        -Change them frequently and find the middle ground.
         
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        • rumblefish360

          rumblefish360 So close, yet so far away

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          Cam selection can be really complicated. It takes a while to learn this stuff. The amount of lobe shapes is , well, crazy. While I’m far from an expert on the subject, I read a lot of the experts words. From there, I can now say I can make a decision while being a little informed.

          A lot depends on what the target is. Driver, hot rod, street/stripper etc.... I get the whole lobe thing pretty good. And the different lobes out there can bend your mind up pretty good. As a basic direction when people ask me about a cam, after the above direction is discussed and the running gear to be used and the cars weight.... A cam can be selected. Hence the many questions asked before such a answer is given.

          For the sake of and just for the sake of simplicity, I can offer the following which is a bit of a over simplification of the matter, but it will work to a large degree for most people out there willing and wanting to take a stab at a cam selection. And if you don’t mind wrenching and experimenting, then by all means, DO IT!
          It was The only way to learn before the internet. And I had a ton-O-fun doing it!

          Duration;

          Is the rpm band. The duration @ .050 lift is a good way (but not the end all) to find out where the cam will generally operate. The rpm band of which it operates in is effected by a few things. Those being:
          Engine size in how the bore and stroke relationship is. A lot of stroke? Lower rpm peaks. Short stroke engine? Higher rpm peaks.
          Cylinder heads stock? Lower rpm peaks. Ported (& how well ported is also a key!) Higher rpm peaks.
          And there’s more kids!! We will leave that for another day.

          A split duration cam can help extend the operating rpm range slightly. It was originally done to help poor flowing exhaust ports. It is possible to use a single pattern cam. (And this is where those dang head flow numbers come in handy.)

          For guys with stock converters, keep the duration @.050 @ 218 or less. You won’t have to change your converter for street duty. That’ll save you some bucks that you should roll over into head work or better heads all together.

          Center line.

          Will produce the rhythm of the exhaust - or not.... LOL!

          At a 112 or higher C line, the idle will be smooth. It is also good for fuel injection, more so on earlier systems.

          At 110 or 108, THAT Muscle Car sound is now present. The idle can be muscular to a little choppy.

          At some 108’s and the lower 106 C lines, the idle can become rough to radical. Lower than that and your probably racing and know this stuff already.

          Lift:

          I always suggest getting as much lift as your heads can handle. More the merry. If your stock or enhanced stock heads flow well to .500, then a .500 lift can will do well.

          If your ported heads flow well to .600, then get a cam that goes to .600. Or as close as possible.


          A little more lift than the head flows isn’t a bad thing. Just keep it limited for most street duty where the car is actually used a lot.
          If your trying to extract more than the average bear on a hot rod, go another .030, street stripper, - .050 inch an lift. Generally I don’t recommend more lift than the head is capable of for street, hot rods and lower powered street strip machines. It’s really not needed. Just grab what you can. It’s a few extra HP over a low lift cam. Since they cost the same.......

          How Quick the valve lifts is also something you should look into. I personally would like to lift the valve by the cams lobe rather than extra rocker ratio because that is extra stress you can avoid on the rocker on down.

          BUT! A quick opening valve is, IS POWER!

          There can be an issue with quick opening valves on low & medium level cars. Noisy valve trains is the biggest complaint. Failed lifters is next I think. I hear it a lot.
          And generally it is not needed even though the engine will appreciate it.
          But I just can’t recommend a super trick, magical atomic bomb cam lobe with a lift that is stupid fast for the average guy here.

          The higher the performance the higher the maintenance!
          Remember that on your current or next build. When it’s with big and radical cams, you will be changing out springs. The more radical the cam and it’s lift, the shorter the springs life span.

          And that’s about it in a nutshell. An over simplification that will work for you on your street car, hot rod & mild to mid level street/stripper. (Small blocks under 500 hp. Which is quit a bit on the street.)

          The MP engines book had a “Tip” section that gave combos with part numbers. And yes, it included cams.

          That’s my take (& story) & I’m stickin to it!
           
          Last edited: Jan 14, 2020
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          • PRH

            PRH Well-Known Member

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            Take everything about your particular combination into account....... then select the lobes and lsa that will best help reach the desired goals and expectations....... and then order it up.:usflag:

            Or......go to the bottom of the page.
             
            Last edited: Jan 14, 2020
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            • my68barracuda

              my68barracuda Well-Known Member

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              This is good stuff. Starting with understanding the target and the vehicle is critical in getting the cam right. The cam characteristics set the personality of the motor. That is why it is important to get it right. At the same time remember, the actual cam is likely in the middle to bottom concerning cost when compared to engine components, and for most engines, the cam can be changed out over an ez weekend. Picking the right cam is not like picking the perfect body color. Get the wrong body paint color (or the wrong body shop) and it can be huge project getting it right. Want to try a different cam,
              not gravy, but not a showstopper.
               
              Last edited: Jan 14, 2020
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              • 273

                273 Well-Known Member

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                Depends on what’s it’s for, highly competitive racing is gonna take R & D lot of trail and error and with your experience probably a good builder in the field along working closely with a cam company.

                less serious race efforts still probably best to try a few different grinds to dial in your combo.

                a weekend warrior can get by with close enough.

                street with little or no race time best off being conservative and going one or two steps down from what a weekend warrior would pick.

                Anything less than what would get you 2hp ish per cfm would be a performance compromise, which is everyone short of full race effort.
                 
              • DentalDart

                DentalDart Well-Known Member

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                ... Um... You lost me after "can be complicated." :rofl:

                I'll just start a camshaft selection thread on FABO if I don't like the one I'm installing and watch the fireworks ensue. :popcorn:
                 
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                • skrews

                  skrews Well-Known Member

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                  The one at the bottom of the page. They save the best for last.
                   
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                  • rumblefish360

                    rumblefish360 So close, yet so far away

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                    To much like an AJ post?
                    :lol:
                     
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                    • Garrett Ellison

                      Garrett Ellison Amateur driver on public roadway, do not imitate.. FABO Gold Member

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                      This thread (or at least the camshaft sounds page) should be a sticky.
                       
                    • 12many

                      12many Well-Known Member

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                      Although my post had a more light hearted intent, and we got some serious reply’s, I will add in all seriousness that “sound” does play a part in cam selection for many. Duh! But, I know from reading many’s posts on this forum that picking a cam for sound is frowned upon as one of the worst criteria for picking a cam. I see nothing wrong with really digging a certain idle cadence, I think that’s the correct term. If you’re say, in the pits at the strip, or a stock car race listening to cars idling and certain ones really give you whatever, goosebumps or a “thrill up your leg” :eek: (not for a certain past president though!) what’s wrong with wanting that? If you can spec a cam along with the performance you want that’s a win win. One with messed up timing to get that? I’ll pass. Making good timing choices, maybe even some concessions for the performance goal along with the idle sound can be done I say. It’s not always about maximizing every last inth sometimes. Hell, I run heavy ass Keystones on my van when I could gain by running some Weld or other lightweight rims. Nope. It’s the looks too. And the same goes for sound. In this instance, give me good timing events on a 106 and I’m good....could listen to that idle all daylong like listening to a babbling brook:thumbsup: Poser out:lol:
                       
                      Last edited: Jan 14, 2020
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                      • rumblefish360

                        rumblefish360 So close, yet so far away

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                        A cam for its idol characteristics or cadence?
                        Sure. Why not?
                        See makers of the radical idle cam(s) below.
                        Howards cams
                        Hughes Engines
                        Comp cams

                        Or like said before, just go to the bottom of the page...
                         
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