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Thread: Cam timing advance?

  1. #1

    Cam timing advance?

    Looking for thoughts from those I trust most, yeah you guys.
    As some of you know I have certainly had some trials and tribulations with my Olds 455. As it stands now, the fresh engine build has proven to be reliable. The issue I’m having is it seems to labor after 3500 RPM. My first thought is a simple ignition timing advance issue. I will certainly be working through that as soon as the lakes thaw.

    The purpose of this post is.
    i received a call from my engine builder yesterday. He also feels something is not as good as it could be. So he’s been researching the issue and is proposing advancement of the cam by 2 degrees. He’s thinking this will help the Olds spin a little easier at those RPM’s above 3500. He’s been great on this project and won’t even give me a bill until we are both happy. Going on 3 years of perfecting this engine. I can’t possibly ask for more than that.

    So Guys, what’s your thoughts on advancing the cam???

    This engine build was straight out of the book “Practical Olds Build” with the most aggressive cam my wet logs would allow.

    According to the chart floating around, this thing is currently making 330hp.

    Thanks in advance

    Bob

  2. #2

    Re: Cam timing advance?

    I am no Olds expert, by any means. But I do understand the attributes of cam timing. as a general rule, advancing the cam timing, will give you a little more on the bottom end, and retarding, the cam, gives you a little more on top. that is if you have the piston to valve clearance to do it.
    It's Impossible to Lose Your Footing, If Your On Your Knees"

  3. #3
    Rob Hawes White Lightning's Avatar
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    Re: Cam timing advance?

    My first thought is fuel being lean at that RPM/throttle opening. If it were me I'd put a wide band O2 meter in the logs and read it at different throttle openings/load situation. It very well may be a carburation problem.
    Rob
    Rob Hawes-Anchorage Rod Works-Anchorage, Alaska
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  4. #4

    Re: Cam timing advance?

    I guess I’ll have to check that too. But it sure seems to be running rich. Only one way to find out.

  5. #5
    Rob Hawes White Lightning's Avatar
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    Re: Cam timing advance?

    Quote Originally Posted by wardjr View Post
    I guess Iíll have to check that too. But it sure seems to be running rich. Only one way to find out.

    What carb are you running?
    Rob
    Rob Hawes-Anchorage Rod Works-Anchorage, Alaska
    "Alaska Hawaii, Shipping Here Is Terrible!" (AH, $hit Club)

  6. #6

    Re: Cam timing advance?

    Holley 750 double pumper

  7. #7
    Rob Hawes White Lightning's Avatar
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    Re: Cam timing advance?

    Quote Originally Posted by wardjr View Post
    Holley 750 double pumper

    Is it doing it at WOT or part throttle?
    Rob
    Rob Hawes-Anchorage Rod Works-Anchorage, Alaska
    "Alaska Hawaii, Shipping Here Is Terrible!" (AH, $hit Club)

  8. #8

    Re: Cam timing advance?

    The thing is, it’s not necessarily doing anything wrong. It simply feels as though it’s fighting itself above 3500 RPM regardless of throttle position. It simply feels “for the lack of a better word” Unhappy. Whether or not it will spin faster is really another issue. But in my limited experience, it should spin easier. If that makes any sense at all.
    For example, before the build and running a really leaky pump. That engine could spool up above 5000 RPM. Now I realize that was mostly due to a lack of load. The point is that it sounded and felt happy doing it. The feel of the new build is as if it is internally laboring.
    What I’ve learned so far is that I probably want to retard (not advance) the cam timing to achieve higher revs. This thing makes loads of torque and pushes the boat with ease. It’ll hop on plan damn near instantly and runs great all the way up to 4400 RPM.
    But as I say it’s not happy about it above 3500. I’m not suggesting that it is doing harm to itself. Just that something isn’t tuned as well as it should be.

  9. #9
    Redeye1620's Avatar
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    Re: Cam timing advance?

    Advancing or regarding the cam to try and achieve your goals is just masking a poor choice of the cam. Get some advice from a custom cam grinder. That's what I did for my ford and couldn't be any happier. The cost was only $50 more than off the shelf cam. Good luck
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  10. #10

    Re: Cam timing advance?

    Sounds like the primary jet is to small.
    76 Marlin Dolphin AMC 401 panther h450
    77 Marlin Dolphin Ford 460 panther g450

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