Can you school me? - Cams...what's what?

Discussion in 'GM Powertrain' started by Springthing, Jul 30, 2010.

  1. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    I baaaaarrreeeely understand cams when it comes to vehicles. I know what they do, I know you can get different ones. But what's the difference?

    Are they able to add HP? Torque?

    What do they mean by an aggressive cam?

    What are the downsides of getting a more aggressive cam?

    Do they have a big influence of the rumble guys like me like to hear trucks (and muscle cars) have?

    Anyone care to share their thoughts, ideas, and comments on the subject? If you get too technical my eyes will glaze over. Any chance you dumb it down for me?

    Thanks in advance!
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Ok well you know that a cam has lobes that open the valves to feed the cylinders.. Basically a cam boils down to 2 different terms "lift" and "duration" there are numbers attached to both of these words that get into the technical side and only mater per motor and use.
    But as the word lift implies it is the amount of Lift that is put into the lifter and therefore how far the valve will open.
    And the word duration (ie:time) is how long the valve is open.
    The higher the lift and duration the more air is pulled into the cylinder and therefore the more "aggressive" the cam becomes. But the more aggressive you make the cam the less streetable you make the motor since it wont idle well, and is designed to make power in a certain range. Hence the loooope looooope looooope, of a modified muscle car at idle sounds as compared to the faster lope lope lope of a truck motor.
    Any cam maker can make a cam that will suite the needs of the user for power in a certain range. Like a truck needs torque down low, and muscle car needs torque and lots of HP in the upper RPMS to make it go really fast
    Then you get into the editorial of Torque and HP.. Where torque is how fast you can go and HP is how fast you get there..
    2 people like this.
  3. j-schmizzle

    j-schmizzle Rockstar 4 Years 1000 Posts

    thanks for the CAMS 101.
  4. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Great post Murdog really hit the nail on the head.
  5. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Nice right up murdog94. If I can add one thing. When shoping for a truck cam you want more increase in lift than in duration for more torque to get the heavy truck moving. I've seen guys put cams made for cars into truck motors and wonder why they don't work well. I always call several cam manufactures to get there recommendations. A few phone calls can save alot of misery.
    1 person likes this.
  6. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Thanks, Murdog! Awesome info to have. Let me post one more follow up questions, then. Would there be any use in getting a cam replaced in a rebuilt/new/crate motor, or should that cam in there be perfect for the application as it?

    Thanks again, great replies.

    STB, also great information to have. I've learned something new today!
  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    The cam supplied with the engine should suffice for your application I dont remember you mentioning a lot of trailer towing, but if you want a little more rumble from your engine your better off putting a new cam in while the engine is out of the truck and you can break in the cam with the rebuilt engine.
    An RV cam could increase mileage and torque and give her a little bit more of a mean sound, big blocks already get a nice rumble with decent mufflers tho.
  8. Als09Sierra

    Als09Sierra Epic Member 5+ Years ROTM Winner 1000 Posts

    This is great info. Murdog that really simplifies it. You mention there are numbers for lift and duration, what kind of ranges would be stock versus a more aggressive cam for a truck?
  9. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

  10. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    As to this i can only really refer you to this site since this is a good explanation, i googled it after seeing this question, since what i know about cams i read when i was a teenager reading about building engines in Hot Rod magazine, and now if i have a specific application i actually call the comp cams guys and have them help me out. So here you go
    This should give you some insite?
    And if you have the AFM (active fuel management), then you really cant do a cam and will actually waste time/money since there is variable valve timing included which uses oil to increase or decrease the needed lift and duration for the best fuel efficency and to run the AFM.
    Basically auto makers are really making it harder and harder to make power NA (naturally aspirated), that is why if people say they want more power and already have headers/tune/cold air/ underdrive/overdrive pulleys/and in the case of the 03 up silverado the Edelbrock fast react Throttle body which opens it something like .05second quicker with partial input and .100 second faster when you drop the hammer all the way. Is to go with forced induction (turbo/supercharger) since the 07 up GM trucks are basically impossible to really modify and not spend more money that the truck will be worth (such as the posted article about the $320K camaro, and that actually uses and old school BBC motor)

    Oh and Spring exactly what TBplus said is what i would do. When the 5.7 in my 98 lets loose that is exactly what i will be doing or if i have the money i will be going with forced induction which will requre a custom grind! BUT i cant type what Tim the Tool man Taylor does but MORE POWER!!! woohooo
    Hope this is some more help.. And thanks a lot for the compliments on the post guys!
    Last edited: Jul 31, 2010

Share This Page

Newest Gallery Photos