Camshaft degreeing 101

Discussion in 'Street/strip 400/430/455' started by Jim Weise, Jan 16, 2011.

  1. Bens99gtp

    Bens99gtp Well-Known Member

    When you hone the mains, if done a few time or takes alot to get it square, the crank moves up closer towards the cam, this can require a shorter chain to keep it tight and the timing events correct.

    The honing process basically involves cutting the caps to make the hole pinched in the vertical plane........so you hone to get round........this removes material from the block causing the crank to now sit in a different distance from the cam.

    Similar processes with rod effecting piston to block distance at TDC
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    You aren’t missing anything. That is exactly what happens and the reason for the smaller chain lengths.
     
  3. 72'lark

    72'lark Active Member

    Thanks guys, the piece of information I was missing is that the caps are machined down in the vertical dimension. I am not familiar with that process and was assuming a tunnel bore or hone changed the internal diameter of the tunnel and would require oversized bearings. All makes sense now.
     
  4. Prairie Piston

    Prairie Piston Well-Known Member

    So it was asked previously and I think I know the answer but.. if a cam is installed straight up and it is one of the 9 out of 10 that is more than 4 degrees out let’s say retarded what is the measures effect. I understand that the torque moves down in the rpm band and in my mind hp must be lost as well. What I am wondering is... has this been quantified? Are we talking 3 hp difference or 20? Besides the torque peak happening earlier...how much is lost?
     
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Unless the cam timing is WAY out, advancing or retarding the cam just moves the power around. Advancing the cam causes all the valve events to occur sooner. Closing the intake valve sooner increases Dynamic Compression, boosting low end at the expense of top end power. Retarding the cam timing does the opposite, it closes the intake valve later which decreases Dynamic Compression and helping top end breathing and HP.
     
  6. SageSenior

    SageSenior Well-Known Member

    Hi Larry
    Would you happen to know how I can contact Mike Pesarchick on the V8 board?
    Thanks
    Tony Saggese
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Sure, he is No Lift,

    https://www.v8buick.com/index.php?members/no-lift.8033/


    Click on "Information", then "Start a Conversation", fill out the form. That will send him a private message on V8.
     
  8. SageSenior

    SageSenior Well-Known Member

    Thank You Larry.
     
  9. Stevem

    Stevem Well-Known Member

    Here’s some other important cam factors that seem to never get talked about, and just note that this info does not come from me but from someone with 60 years of making top notch power and writing a Cam program in 1997 that is based on his 35 years of juggling cams to find the best ones.

    The amount of overlap is a big determinent in how high the motor will rev and for any given amount of overlap there is a minimum compression ratio needed.

    There are two other determining factors 1) if it’s solid lifter cam or a hydro cam.

    Here’s a example for a 425 cid motor.
    To go to 6000 rpm with a solid cam it needs 72 degrees of overlap and a minimum 10 to one compression.
    This 72 degrees is determined by the numbers at .020” tappet lift which is what most solid lifter cams numbers are stated at.
    In terms of a hydro cam for this same 425 motor and due to these cam’s numbers to use are at .006” lift you would need to add 10 more degrees to that 72 needed for a solid cam.

    If you want this 425 with a solid lifter cam to go to 7000 rpm then the cam would need 80 degrees of overlap and a minimum of 12.5 compression.
    Note that this is not to say that any given motor will not rev to what I have used for a example of rpm, but for any given overlap amount if you do not have the needed compression then motors Hp it produces will long since have nosed way over by the time the target rpm is reached.

    a long with that too low of a compression will make for a weak torque band .
     
    Last edited: Feb 21, 2024
    VET, Mart and Dano like this.
  10. Mart

    Mart Gold level member

    Good!
     
  11. gsgtx

    gsgtx Silver Level contributor

    you thing they would do it at .050. at .006 the .050 numbers can be all over the place with the ramp speed of the cam. the .050 numbers will give you a more accurate power of the cam. I could be thinking wrong here. the compression part makes sense.
     
    Last edited: Feb 21, 2024
  12. gsgtx

    gsgtx Silver Level contributor

    different cams have different lifts with the same overlap. lift affects power range right.
     
  13. Tomahawk

    Tomahawk Platinum Level Contributor

    Lobe Seperation Angle and duration determine when the intake valve opens and when the exhaust valve closes which, if present, is overlap. For example, if the intake valve opens 8* BTDC and the exhaust valve closes 8* ATDC, the cam has 16* of overlap. If the intake & exhaust valves are not open at the same time, the camshaft does not have overlap.

    LSA, duration, and ICL (if installed advanced or retarded) are the most significant contributors to the cam's power range.
     
  14. 87GN_70GS

    87GN_70GS Well-Known Member

    If one were to spend time on the SpeedTalk forum one would realize there is not much truth to this. Overlap has very little to do with maximum rpm capability, but instead has to do with intake and exhaust duration amount.
     
  15. wkillgs

    wkillgs Gold Level Contributor

    Can Hyd and solid cams specs be directly compared, or do you generally 'subtract 10* @ 0.050" for a solid for sake of comparison ?

    Adv duration for a hyd is determined at 0.006" lift, a solid is 0.020" lift (and with 0.012" lash).
    @ 0.050", a hyd has had (0.050- 0.006)= 0.044" movement, while a solid has (0.050- 0.012)= 0.38" movement.
    Is that difference in initial lift completely compensated for in the ramps, or should we include that -10* 'adjustment factor' for a solid?

    Comp describes their cams based on their advertised duration, not the 0.050" duration. Joe pointed this out to me when I was looking at a solid.... he said go up one series when switching to a solid.

    It seems like manufactures should use a different lift point for their solid grinds, not the usual @ 0.050" duration.
    Is this correct?
     
  16. Guy Parquette

    Guy Parquette Platinum Level Contributor

    To degree my cam in correctly, 4 degrees advance. Had to skip a tooth and go from there with the 9 tooth gear set. I believe this is what makes a fast Buick versus a slow Buick. It’s a must do deal!
     
  17. VET

    VET Navy Vet, Founders Club

    I know this is a dumb question.
    Is there a major difference between a aspirated engines and engines that are turbo charged and supercharged?
    What i'am getting at, is there a major difference in the camshafts in these engines and compression rates?
    I noticed on the Red Eye Dodges that have huge amounts of horsepower and run in the 10 second and lower ET bracket, they don't have that bad ass cam rump. Why is that?
    I'am assuming they are using
    Hydraulic cams, yes/no?
     
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    My guess is variable valve timing.
     
    Guy Parquette likes this.
  19. DaWildcat

    DaWildcat Platinum Level Contributor

    That and high pressure direct fuel injection, not to be confused with the usual manifold FI.

    And we're all enjoying forced induction at ~14.7 psi depending on where you live. Bump that up a few psi with a compressor, and big power is available without sacrificing the drivability that a big duration, high overlap cam brings us.

    If you want even more, keep adding to the the forced induction and also add the valve open duration and overlap. The whole concept of having both valves open a bit is that the inertia of exiting exhaust can help draw in fresh air/fuel over and above what is pushing from the intake side.

    It's a matter of diminishing returns though, as exhaust gasses, while forced out by the piston, still face that same ~14.7 psi on the way out.

    Devon
     
    Last edited: Feb 23, 2024
  20. VET

    VET Navy Vet, Founders Club

    That's amazing coming from forced induction power.
    I wonder if the torque numbers are also high?
    I have to get a ride in a Red Eye to feel the power.
    That said, I love the rump of a cam. Having no cam rump, just feels strange in a muscle car. Vet
     
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