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Someone please explain camshafts to me!

Discussion in 'The Garage' started by johnnieg, Jan 8, 2004.

  1. johnnieg

    johnnieg 1/2 ton status

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    I was looking on Jegs at a Comp Cams Extreme 4X4 cam but don't understand how lift, grind and duration affect performance. Also, how hard is it to swap a cam? Do I have to pull the engine? Are there any other mods I need to do in order to get the best performance out of it?
    Here is a link to the Jegs product list click here
     
  2. SUBFAN

    SUBFAN 1/2 ton status

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    You should be looking at cams that are designed to work with your computer....

    At this time, the best advice I can give you is to go to the Comp Cams web sight, and fill out one of their reccomendation forms. In a few days, they will give you what they recommend.

    BE HONEST when you fill that thing out.... /forums/images/graemlins/thumb.gif
     
  3. gravdigr

    gravdigr 1/2 ton status

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    and swapping a cam does not require pulling the engine. But you will need to remove the radiator and grill along with everything on the front of the motor to get the timing chain cover off as well as the intake and valvecovers to get the lifters and pushrods out.
     
  4. Z3PR

    Z3PR Banned

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    249-CL12-239-3 ******************************************************************************* Grind: 262
    Duration: 218°/226°
    Lift: .462''/.480''
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    and swapping a cam does not require pulling the engine. But you will need to remove the radiator and grill along with everything on the front of the motor to get the timing chain cover off as well as the intake and valvecovers to get the lifters and pushrods out.

    [/ QUOTE ]

    You'll also have to cut the radiator support or beat it out of the way, because a cam won't come out otherwise.

    To further understand camshaft specs, check out www.compcams.com, there is a through explanation of how all the specs factor in.

    If you're unsure of what cam you should use, call them. They'll give you a recommendation.
     
  6. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    OK, to help you understand cams when reading specs, here are a few ideas to help you:
    bigger cubic inch motors like bigger lift cams. for example.
    A 350 SBC with a 454" lift 218 duration cam will make a lot of midrange power along with being torquey but also having good top end. A 454 big block would need a bigger cam like around 480 to 500" lift to make it's power in the same RPM range as the smaller 350. make any sense? It takes more lift and gas/air to feed more cubic inches.

    Using a 350 and looking at cam numbers, you would get...

    a good idle, nice torque, good fuel mileage would be like a 400" to 420" lift 200 to 210 duration cam.

    a noticeable idle, more power and torque, does a little better with a good breathing exhaust and intake would be like a 440" to 470" cam. and 215 to 220 duration.

    a rougher idle, lots of middle to upper RPM horsepower, needs good breathing components and a stall converter, would be like 480" to 520" lift with 224 to 244 duration.

    very rough(pumped classic muscle car) idle, big upper RPM power, needs good breathing components and a high stall converter, would be like 550" plus lift and 255 plus duration.

    I wen't off comp cams energy and magnum cam series, I highly recommend comp over anybody else. /forums/images/graemlins/thumb.gif
     
  7. Z3PR

    Z3PR Banned

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    [ QUOTE ]
    I highly recommend comp over anybody else.

    [/ QUOTE ] Highly agree, Comp cams are #1 in my opinion. /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    rjfguitar,

    You're a little bit off. Lift has nothign to do with the size of the engine. Although cams with more duration usually also have more lift, this is not always the case. Compare one of Comp's more agressive cams like the Xtreme Energy series to a standard cam and you'll see that more lift and less duration still makes a torquey motor, even with high lift numbers. Simply looking at one specification doesn't give you enough information about the cam.

    One thing that should always be considered is lobe seperation angle. Two cams that a are seemingly similar in specs except for lobe seperation can be drastically different.
     
  9. Thunder

    Thunder 3/4 ton status

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  10. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    rjfguitar,

    You're a little bit off. Lift has nothign to do with the size of the engine. Although cams with more duration usually also have more lift, this is not always the case. Compare one of Comp's more agressive cams like the Xtreme Energy series to a standard cam and you'll see that more lift and less duration still makes a torquey motor, even with high lift numbers. Simply looking at one specification doesn't give you enough information about the cam.

    One thing that should always be considered is lobe seperation angle. Two cams that a are seemingly similar in specs except for lobe seperation can be drastically different.

    [/ QUOTE ]
    I agree about the lobe seperation and I don't know a ton about cams but I do know some about lift and duration and that an "agressive" cam in a 350 and a 454 with the same specs as the 350 seems milder in the 454 than the 350.
    from what I have seen, big blocks just take more lift and duration to make power in the same RPM range and same characteristics as a small block with a smaller cam. The biggest small block cam I have ever seen was like 650" lift and the biggest big block cam I have seen had like 833" lift.

    I wasn't really trying to explain a bunch of technical stuff to the guy...just try and give him an idea on getting familiar with cam numbers and being able to relate them to what characteristic it would give in a motor. /forums/images/graemlins/smile.gif
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Generally speaking, it's the duration that makes the most difference in RPM range and what is tolerated by what size engine. More lift usually comes automatically with more duration, but this isn't always the case, and in recent years, more and more shorter duration cams are coming with more lift (which means faster ramps) which equals more vacuum and more torque for us!!
     
  12. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Well then I will be in good shape when I go AFR heads with 1.6 ratio roller rockers. That will bring me to 218 duration and 484" lift. /forums/images/graemlins/thinking.gif
     

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