CFM for 8-71
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CFM for 8-71

  1. #1
    Junior Member Lotsahorsepower's Avatar
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    Default CFM for 8-71

    Will twin Holley 750's deliver enough fuel for a 600 C.I. Big M,
    Dart 320's,.660 lift roller,8-71 starting at 1:1 overdrive
    in a 26Ft. DCB Cat? Got the boat used with this combo
    but I sure would like a second or third opinion.

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  3. #2
    gn7
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    Quote Originally Posted by Lotsahorsepower View Post
    Will twin Holley 750's deliver enough fuel for a 600 C.I. Big M,
    Dart 320's,.660 lift roller,8-71 starting at 1:1 overdrive
    in a 26Ft. DCB Cat? Got the boat used with this combo
    but I sure would like a second or third opinion.
    LINK: Blower carb sizing



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    not with the big m. sorry just kidding.

    I would think you need min of two 950 or a pair of doms modded for blower app. and i feel your going to have to spin a 8-71 over quite a bit to fill 600 cubes. also i would check the rest of the full system can provide anough full to feed such a monster and keep your investment from burning a few pistons up.

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  6. #4
    gn7
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    The 750's are good to about 6000 Rs at 1 to 1 on the blower. If you spin the motor or blower faster, your going to need more carb. The 8-71 on a 600 incher is good for about 5lbs boost at 1-1, if it is good shape. Maybe 6 if it is fully stripped.



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    Junior Member Lotsahorsepower's Avatar
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    The Supercharger is fully striped and fresh.
    I hope the weather holds out long enough to
    finish the rigging and get a few runs in this year.
    Boating in Ohio is short but SWEET.

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    You could make alot of power with the blower and bigger carbs. 850 cfm holleys or more . Search the internet. I run dominators. Blowers love dominators.

  9. #7
    gn7
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    Quote Originally Posted by gn7 View Post
    The 750's are good to about 6000 Rs at 1 to 1 on the blower. If you spin the motor or blower faster, your going to need more carb. The 8-71 on a 600 incher is good for about 5lbs boost at 1-1, if it is good shape. Maybe 6 if it is fully stripped.
    Quote Originally Posted by DEL51 View Post
    You could make alot of power with the blower and bigger carbs. 850 cfm holleys or more . Search the internet. I run dominators. Blowers love dominators.
    I don't think Lotsahorsepower misunderstood this. But some did.
    It won't make one HP more with 950s or Dominators, unless he speeds up the blower or runs the engine passed 6000.

    Maybe this is lost on some, but you aren't feeding a motor. Your feeding a blower. A 8-71 running 6000 Rs can't move 1500cfm. So what good is 2 Dominators.



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    Blowers love the Big Carbs, Maybe it is more than a stamped cfm number on the box. But with my experience the more the better. Wanna Fight?

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    gn7
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    Quote Originally Posted by gn7 View Post
    The 750's are good to about 6000 Rs at 1 to 1 on the blower. If you spin the motor or blower faster, your going to need more carb. The 8-71 on a 600 incher is good for about 5lbs boost at 1-1, if it is good shape. Maybe 6 if it is fully stripped.
    Quote Originally Posted by DEL51 View Post
    Blowers love the Big Carbs, Maybe it is more than a stamped cfm number on the box. But with my experience the more the better. Wanna Fight?devil
    No. I don't care to fight. Your the one with the knowledge here. I want you to tell me how a 8-71 turning 6000 Rs can move more air thru a set of Dominators than it can thru a set of 750s. How many cfm does a 8-71 move in one revolution. Its fixed. It can only move so much per revolution, and no more. So how many CFM per revolution.



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    Quote Originally Posted by gn7 View Post
    No. I don't care to fight. Your the one with the knowledge here. I want you to tell me how a 8-71 turning 6000 Rs can move more air thru a set of Dominators than it can thru a set of 750s. How many cfm does a 8-71 move in one revolution. Its fixed. It can only move so much per revolution, and no more. So how many CFM per revolution.
    I KNOW , I KNOW ,

  13. #11
    just a ski boat with bark Carnivalride's Avatar
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    Quote Originally Posted by Lotsahorsepower View Post
    Will twin Holley 750's deliver enough fuel for a 600 C.I. Big M,
    Dart 320's,.660 lift roller,8-71 starting at 1:1 overdrive
    in a 26Ft. DCB Cat? Got the boat used with this combo
    but I sure would like a second or third opinion.
    This formula gives you the cfm requirement
    ((cid x rpm)/3456) x ((boost/14.7)+1) = required cfm
    example:
    ((600 x 6000)/3456) x ((6.5lbs/14.7)+1)
    ((3600000/3456) x ((.442177)+1)
    (1041.667 x 1.442177) = 1502cfm


    note: this is much easier when plugged into an excel spreadsheet.
    Quote Originally Posted by gn7 View Post
    Carnivalride, you really need to find some other hobby. You have no talent for this boat thing

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    Senior Member Hallett's Avatar
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    didn't want to run dominators when I built my blown 598 I talked to a few people
    decided to run 1050 4150's quick fuel carbs gave them all the motor info had them
    wet flowed seem to work real nice. no need for dominators

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    gn7
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    Its not a matter of running Dominators or not. Its a matter of if the blower needs that much carb. Curious Hallett. What is it you don't like about Doms


    As Carnivalride posted, its about 1500 cfm on 600 inch motor running a 8-71 turning 6000 RPM blower speed. My formula comes up with 1467, which is close enough. Havasubyou seems to think it needs 2100. Don't know why he thinks that. I'm certain he some pretty vast knowledge carbing a supercharger that has escaped BDS, RBS, and the Blower Shop.



    Carnivalride: What I really want was the CFM per revolution of a 8-71.
    Del51, feel free to jump in.



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    Last edited by gn7; 09-29-2010 at 09:50 AM.

  16. #14
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    Quote Originally Posted by alkyexpress View Post
    I KNOW , I KNOW ,
    PICK ME, PICK ME!! I don't doubt for one second you do



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