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  1. #1
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    Short flame arrestor HP 500

    Does anyone have any calculations on flame arrestor size and CFM?

    My brother is dropping the HP 500 in his 22 Donzi today. His old one is off a 525 SCI and we're pretty confident it is too tall to fit under the hatch... I think it is a 3" unit.

    I see Gaffrig makes a few 2" arrestors, but what is the right size to get? What kind of power loss, if any?

  2. #2
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    I have a eddie marine 8x2 s/s about as short as I've seen for a h/p use

  3. #3
    Charter Member # 55 Charter Member Griff's Avatar
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    If you go from 3" to 2" height, increase the diameter of the arrestor by about 1/3.

    An 8x3 arrestor has about 75 square inces of surface. A 12x2 has about the same.

  4. #4
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    Quote Originally Posted by Griff View Post
    If you go from 3" to 2" height, increase the diameter of the arrestor by about 1/3.

    An 8x3 arrestor has about 75 square inces of surface. A 12x2 has about the same.
    Is it strictly surface area or does the height / bend have something to do with it? I figured it was more than just surface area.

  5. #5
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    Causing the air to make a 90 degree bend is never a good thing. Thats why people run stacks when possible. But if your limited.....your limited. Not much you can do about that.



    Darrell.

  6. #6
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    Quote Originally Posted by DMOORE View Post
    Causing the air to make a 90 degree bend is never a good thing. Thats why people run stacks when possible. But if your limited.....your limited. Not much you can do about that.



    Darrell.
    very true. if it is between a few HP and a hole in the hatch the HP loses.

  7. #7
    Charter Member # 55 Charter Member Griff's Avatar
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    I doubt you will notice any difference in performance. It might cost you 5-8 hp which equals next to nothing in mph.

  8. #8
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    I went to a Gaffrig 10X2 for hatch clearance from a Merc 10X3. I ran the boat with it and without it on the same day with no change in performance. BTW Merc sells the stickers if you want it to look stock

  9. #9
    SB
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    If you still have choke towers on your Holley I'd sweat with a 2" unit.

    FYI: Ran a 350hp SBC 20ft boat on a bunch of tests, back to back runs the K&N 9x4 arrestor lost just over 1mph vs no arrestor.

  10. #10
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    Quote Originally Posted by SB View Post
    If you still have choke towers on your Holley I'd sweat with a 2" unit.

    FYI: Ran a 350hp SBC 20ft boat on a bunch of tests, back to back runs the K&N 9x4 arrestor lost just over 1mph vs no arrestor.
    Yup-I agree, my dominator carb does not have a choke tower.


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