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Thread: New 408.......no bottom end

  1. #26
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    Snap on scanners read sync backwards, where if it's plus 5 it's actually minus 5 . Set sync to 0 .
    In my opinion the Keith Black pistons are trash. Always use forged. With that cam your compression is low. You need 10.5 to 1 . Your tune is an issue, plus check gearing. Good luck.

  2. #27

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    Quote Originally Posted by packard1 View Post
    Snap on scanners read sync backwards, where if it's plus 5 it's actually minus 5 . Set sync to 0 .
    In my opinion the Keith Black pistons are trash. Always use forged. With that cam your compression is low. You need 10.5 to 1 . Your tune is an issue, plus check gearing. Good luck.
    I appreciate the reply.

    Never heard that about the snap on scanners. Seems odd that it would read backwards. I will try to get it to 0. I imagine that clockwise would advance and counter clockwise would retard?

    I didn't know Keith Black pistons were bad. I had read that had the highest amount of silicon in their alloy content which made them one of the better hypereutecnics available.

    Also as far as compression goes, it seems my research told me to keep my dynamic ration at less than 8.0:1 for pump gas. I am right there with my static compression and my current cam.

    Perhaps this is archaic literature and I read too much! It does seem that many people are running well over 10.5:1 on magnum motors with pump gas without problems. I believe too that most people are making a general guess at their compression when they say what it is. Piston dish, Cylinder head CC, head gasket thickness, piston to deck, gasket bore, top ring land depth......short of taking every single one of these measurements I think a lot of people could be off from what they think.

    I have heard of one 408 from PIE that has some pinging at 10.5:1 with aluminum Edelbrock heads but that could be the fuel or timing of course.

    Had to purchase a computer and have HP Tuners coming next week so I will begin the journey of learning to tune.

  3. #28
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    Quote Originally Posted by thomasfouraker View Post
    I appreciate the reply.

    Never heard that about the snap on scanners. Seems odd that it would read backwards. I will try to get it to 0. I imagine that clockwise would advance and counter clockwise would retard?

    I didn't know Keith Black pistons were bad. I had read that had the highest amount of silicon in their alloy content which made them one of the better hypereutecnics available.

    Also as far as compression goes, it seems my research told me to keep my dynamic ration at less than 8.0:1 for pump gas. I am right there with my static compression and my current cam.

    Perhaps this is archaic literature and I read too much! It does seem that many people are running well over 10.5:1 on magnum motors with pump gas without problems. I believe too that most people are making a general guess at their compression when they say what it is. Piston dish, Cylinder head CC, head gasket thickness, piston to deck, gasket bore, top ring land depth......short of taking every single one of these measurements I think a lot of people could be off from what they think.

    I have heard of one 408 from PIE that has some pinging at 10.5:1 with aluminum Edelbrock heads but that could be the fuel or timing of course.

    Had to purchase a computer and have HP Tuners coming next week so I will begin the journey of learning to tune.
    There is a lot that goes into how much compression ratio you can run with pump gas, it's not just compression:

    - Piston top design
    - Head chamber
    - Head material
    - Type of fuel injection
    - Quench area
    - Cam timing (intake lobe split, open/close events)
    - ECU software/programing, spark advance, timing
    - Rod ratio/dwell time (how long the piston is at top dead center)

    Not all these things contribute equally, some have a greater effect than others. Our 5.9s generally with Edelbrock heads and stock pistons can run 10 to 10.5 with about any cam on pump gas. If you want to go higher that on pump gas, you should start talking to the cam manufacture to make sure your intake lobes will bleed off enough compression so you don't have problems.

  4. #29
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    Quote Originally Posted by musky mike View Post
    There is a lot that goes into how much compression ratio you can run with pump gas, it's not just compression:

    - Piston top design
    - Head chamber
    - Head material
    - Type of fuel injection
    - Quench area
    - Cam timing (intake lobe split, open/close events)
    - ECU software/programing, spark advance, timing
    - Rod ratio/dwell time (how long the piston is at top dead center)

    Not all these things contribute equally, some have a greater effect than others. Our 5.9s generally with Edelbrock heads and stock pistons can run 10 to 10.5 with about any cam on pump gas. If you want to go higher that on pump gas, you should start talking to the cam manufacture to make sure your intake lobes will bleed off enough compression so you don't have problems.
    ^^this x2
    Flame propagation has a lot to do with what 'compression' you can run.

  5. #30
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    But seriously. Tune it first.

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    Quote Originally Posted by niebs View Post
    ^^this x2
    Flame propagation has a lot to do with what 'compression' you can run.
    That would be the first three on the list and quench. +1 on tune it first.

  7. #32



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    And how is your buddy, or you going to "tune" this thing?
    Asking for a friend of a friend,

    EDIT:
    - Piston top design
    - Head chamber
    - Head material
    - Type of fuel injection
    - Quench area
    - Cam timing (intake lobe split, open/close events)
    - ECU software/programing, spark advance, timing
    - Rod ratio/dwell time (how long the piston is at top dead center)

    DAFUQ.....LOL
    Just tune the fucking thing.
    11.27 @ 118.23
    2017 NM Mopar Challenge Series Champion

  8. #33

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    Quote Originally Posted by Adobedude View Post
    And how is your buddy, or you going to "tune" this thing?
    Asking for a friend of a friend,

    EDIT:
    - Piston top design
    - Head chamber
    - Head material
    - Type of fuel injection
    - Quench area
    - Cam timing (intake lobe split, open/close events)
    - ECU software/programing, spark advance, timing
    - Rod ratio/dwell time (how long the piston is at top dead center)

    DAFUQ.....LOL
    Just tune the fucking thing.
    HPTuners MPVI2 interfaced with AEM wideband through serial output to the software.
    We are going to get the fuel tables friendly over a few days. He has a draggy which will help gather performance data in relation to adjustments made. Then when we have it close I will rent a local dyno $100/hr to dial it in. Lots of information out there on how to tune. He has a considerable amount of experience tuning, just not in a jtec platform.

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