Header primary size ????????
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Header primary size ????????

  1. #1
    Boat 502 76Miller's Avatar
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    Default Header primary size ????????

    Bassett offers a 2 1/2'' and the common 2 1/4'' when do you step up ??? If the motor is n/a and not blown is there any gains with the bigger primary ???? has anybody tested this on a dyno ??

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    Senior Member vee-driven's Avatar
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    i would say 2 1/4 with a n/a motor, because i think a little back pressure would be good.


    It's not that i don't care, I just dont give a sh!t!

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    Boats N Hoes Brad22CP's Avatar
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    What cubic inch?

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    Jackwagon Patrolman Rexone's Avatar
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    2 1/4 will yield more HP on most any N/A engine unless it's a prostock or something very radical. 1 7/8" or 2" actually works better on most but they don't offer them any more since water injection came about.

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    Boat 502 76Miller's Avatar
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    Quote Originally Posted by vee-driven View Post
    i would say 2 1/4 with a n/a motor, because i think a little back pressure would be good.
    Pat, your probably right. I was hoping maybe somebody has tested it before I buy another set of 2 1/4'' .

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    Boat 502 76Miller's Avatar
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    Quote Originally Posted by Brad22CP View Post
    What cubic inch?
    Its a 533ci. n/a jet boat.

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    Boat 502 76Miller's Avatar
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    Quote Originally Posted by Rexone View Post
    2 1/4 will yield more HP on most any N/A engine unless it's a prostock or something very radical. 1 7/8" or 2" actually works better on most but they don't offer them any more since water injection came about.
    Rex, have you actually tested this ??? Does more exhaust "scavaging" take place with the smaller pipe ? Just figured if there is gains to be made, the price difference is not much.

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    Jackwagon Patrolman Rexone's Avatar
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    Quote Originally Posted by 76Miller View Post
    Rex, have you actually tested this ??? Does more exhaust "scavaging" take place with the smaller pipe ? Just figured if there is gains to be made, the price difference is not much.
    I have not personally but have spoken with many who have over the years. 2" is generally considered about optimum (dry). When you add water 2 1/4" seems to work good. Note that all engines are different. If you have huge cam and heads you may need something larger. 2 1/2" on most N/A engines though would be considered too big. Only the dyno knows for sure on this though.

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    On a 409 1 7/8" seems optimum...2" looses power until over 6K rpm.

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