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The difference between these?

This is a discussion on The difference between these? within the Internal Engine forums, part of the LSx Technical Help Section category; Besides the obvious change in lift and LSA. 248/254 629/622 113 248/254 622/614 112 I am guessing they would be ...

  1. #1
    Slow'er'Ass Mr. Luos's Avatar
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    The difference between these?

    Besides the obvious change in lift and LSA.
    248/254 629/622 113

    248/254 622/614 112


    I am guessing they would be almost the same driveability and power output. Am I right?

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    down with the lot lizards blackhawk01's Avatar
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    I would say that the bottom one would give you better torque in lower RPM's, and the top one would probably give you better torque in the higher RPM's....hell i dont know lol just a guess

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    could you ask for a dyno profile from the mfg?

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    Whose lobes are they? Not all lobes are created equal

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    Senior Member Wheeler99WS6's Avatar
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    I would think they would be within a couple hp of the other. Yeah the lift is minutely different but with the 112 LSA (lower lift) the powerband would come a tad sooner so the lower lift wouldnt make too much of a difference except on top end I would say. Just my .02$

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    Slow'er'Ass Mr. Luos's Avatar
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    Quote Originally Posted by Marc 85Z28 View Post
    Whose lobes are they? Not all lobes are created equal
    Comp XE-R blanks.

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    Moderator Firebirdjones's Avatar
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    There are alot of hidden variables not listed, such as intake centerline,,,telling you whether or not there is any advance ground into the camshaft as compared to the LSA. This could make these 2 cams completely different in power band and HP output.

    As mentioned, the ramp profiles can be changed as well. Comp has a new style ramp out that has a faster opening rate but closes the intake valve sooner on the back side of the lobe.

    You would really need the cam card to closely compare the 2 camshafts.

  8. #8
    Quote Originally Posted by Mr. Luos View Post
    Comp XE-R blanks.
    For both cams? If so power and driveability should be near identical. The only difference would be where in the RPM range the power occurs due to ICL and LSA differences - and that would be minimal.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Marc 85Z28 View Post
    For both cams? If so power and driveability should be near identical. The only difference would be where in the RPM range the power occurs due to ICL and LSA differences - and that would be minimal.
    Intake centerline and Lobe seperation angle differences minimal???

  10. #10
    Quote Originally Posted by Firebirdjones View Post
    Intake centerline and Lobe seperation angle differences minimal???
    When talking about only a degree or two as we are here, absolutely!

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Marc 85Z28 View Post
    When talking about only a degree or two as we are here, absolutely!
    We aren't talking a degree or 2 here though. The intake centerline was not listed with these cams in this post,,,,only the Lobe seperation angle,,,which of course is only 1 degree change...but there isn't an intake centerline listed so we really don't know how many degrees we are actually talking about here.

    Knowing the intake centerline is also important when selecting camshafts,,,as this tells you how much (if any) advance is ground in the camshaft,,,,and gives you an idea of where the installed position should be.

    These cams may have 112 or 113 degrees of lobe seperation but the intake centerline could possibly have for argument sake lets say,,,,108 degrees,,,which would mean the 112 lobe seperation cam would already have 4 degrees of advance in it.

    Then lets say the 113 lobe seperation camshaft has 113 degrees of intake centerline,,,,which tells you this cam has no advance at all in the grind. It could even go the other way and have retard in it.

    With that said,,,,installing both of these cams in the straight up position,,,,would yield two completely different acting camshafts,,,,one with 4 degrees of advance and the other with no advance,,,,,which in turn changes the outcome.

    The cam with 4 degrees of advance in the grind,,,,would produce more torque down low,,,,a little less HP and torque up high. Also the advance would help to produce a little smoother idle,,,a little more idle vacuum,,,and also creates more cylinder pressure,,,this also moves the intake valve closer to the piston,,which makes piston to valve clearance an issue and needs to be checked.

    What I was getting at is,,,,,these intake centerline numbers are not listed,,,so to ask how these camshafts compare is nearly impossible to answer without more information,,,,notably from the cam card.
    Last edited by Firebirdjones; 01-14-2008 at 04:36 AM.

  12. #12
    I understand all that But even if there is a 4 degree difference between the two cams, we're talking about the powerband moving up or down only a few hundred RPM at most. And a single degree difference in LSA or ICL will affect idle quality, but again will be so minimal it's hardly noticable. IMO you're focusing too much on the details and losing sight of the overall picture. I could be dead wrong, but most cams that size for that particular engine have an ICL that varies no more than 2 degrees from the LSA, and it's usually advanced.
    Last edited by Marc 85Z28; 01-14-2008 at 06:23 AM.

  13. #13
    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Marc 85Z28 View Post
    I understand all that But even if there is a 4 degree difference between the two cams, we're talking about the powerband moving up or down only a few hundred RPM at most. And a single degree difference in LSA or ICL will affect idle quality, but again will be so minimal it's hardly noticable. IMO you're focusing too much on the details and losing sight of the overall picture. I could be dead wrong, but most cams that size for that particular engine have an ICL that varies no more than 2 degrees from the LSA, and it's usually advanced.
    It's the details like this that seperate the fast cars from the extremely fast cars.

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    Slow'er'Ass Mr. Luos's Avatar
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    Okay, both grinds are called the same name. The 112LSA version is just an newer version.
    I 'assume' they are VERY similiar.

    Thinking I will jump up on the duration a little anyways.

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