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Thread: 496 HO Headers

  1. #1
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    496 HO Headers

    I recently purchased an F29 DCB with Twin 496 HO Motors. And love everything about the boat except the hole shot. I am looking for a bit more kick out of the hole.

    Has anyone out there installed any of the following and what kind of increase/decrease did you get?

    CMI Headers, Dana Marine Vortex Exhaust or Hardin Marine Headers? All claim appx 48 HP increase per motor.

  2. #2
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    Here's a link to an article I wrote after extensive testing. Unfortunately I wasn't able to get a set of the CMI's to test.

    http://fullthrottlemarine.com/496%20...%20Article.htm

    You will notice a significant low end torque improvement, especially with the tubular headers.

  3. #3
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    Excellent information. Thanks for sending. Anyone out there have CMI header stats like this I can look at?

  4. #4
    Platinum Member Platinum Member verbi69's Avatar
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    What kind of HP #'s would be had if the computer was not remapped and the 496 run with 87 octane....and only run to the 5000-5100 rpm insted of 5400 rpm??
    thanx,
    mike
    Lazy & Crazy

  5. #5
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    You'd lose about 20-25 HP running the stock HO program.

  6. #6
    Commercial Member Commercial Member HaxbySpeed's Avatar
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    I put a set of CMI sport tubes and a K&N arrestor on a 496HO in a 22' donzi classic. It picked up 3.5mph. The boat is quite light so it's hard to judge holeshot but the midrange acceleration is noticeably stronger. Hope that helps...

  7. #7
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    I put a set of Dana exhaust on my 496HO Donzi 22 classic picked up 1-2 MPH more mid range torgue, and about 300 rpms. also went from a 25 pitch prop to a 26P......oh it also sounds good too....

  8. #8
    Platinum Member Platinum Member verbi69's Avatar
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    Thanks bobl....I actually printed your article a couple of weeks ago as I found it interesting. I want to put a Raylar 103 kit in my silencer this winter if not shortly. The only thing I dont want to do is run 5500 rpm or 93 octane fuel or race gas......headers are still a thought too along with the 103 kit. All this info helps...
    Thanx,
    mike
    Lazy & Crazy

  9. #9
    Offshoreonly Advertiser Offshoreonly Advertiser Whipple Charged's Avatar
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    Quote Originally Posted by verbi69 View Post
    What kind of HP #'s would be had if the computer was not remapped and the 496 run with 87 octane....and only run to the 5000-5100 rpm insted of 5400 rpm??
    thanx,
    mike
    20-25hp between 5000 and 5400.

  10. #10
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    Headers for sure CMI's are tested and true.

    Im sure you know that if you prop it down you will gain inital pick up but loose top speed.

    I'd say do the headers first and then go from there.


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