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Original Message
CFM formula
By Bob - 04/11/2005 5:33:56 PM; IP 138.163.0.44
Take the radius of the bore squred times pie times the length of the stroke times the number of cylinders. This computes the CID. You need to figure this out because it will change every time the motor bore and stroke changes.

R Sqrd X Pie X length X # cyl= CID.

Take the CID and divide it by 1728.There are 1728 CI's for every cubic foot. Since CFM deals with cubic feet you convert this.

427/1728=.247=CFD

What you need to know now is the the MAX RPM, redline RPM.

Take the CFD and multiply by half of the MAX RPM this will give you the proper CFM carb for the motor. Lets say the redline is 5500 RPM.

.247 X (5500/2)= CFM

.247 X 2750=679 CFM
This thread, so far...
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Collapse <a href=../ForumFE/reply.aspx?ID=24488&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24488" onclick="return false;">which carbs to use BJ/BK or BC/BD?</a>&nbsp;-- <font color=#0000ff>Greg Westphall, <i>04/08/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24488', contentMargin: 60, icon: $('anchor24488') }); </script>  which carbs to use BJ/BK or BC/BD? -- Greg Westphall, 04/08/2005
 My suggestion is BJ/BK based on: -- Wayne K., 04/08/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24497&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24497" onclick="return false;">I use the BJ /BK</a>&nbsp;-- <font color=#0000ff>Royce, <i>04/10/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24497', contentMargin: 60, icon: $('anchor24497') }); </script>  I use the BJ /BK -- Royce, 04/10/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24502&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24502" onclick="return false;">What camshaft might you recommend?</a>&nbsp;-- <font color=#0000ff>Greg Westphall, <i>04/10/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24502', contentMargin: 60, icon: $('anchor24502') }); </script>  What camshaft might you recommend? -- Greg Westphall, 04/10/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24506&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24506" onclick="return false;">RE: What camshaft might you recommend?</a>&nbsp;-- <font color=#0000ff>giacamo, <i>04/10/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24506', contentMargin: 60, icon: $('anchor24506') }); </script>  RE: What camshaft might you recommend? -- giacamo, 04/10/2005
 RE: What camshaft might you recommend? -- walt, 04/26/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24507&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24507" onclick="return false;">RE: What camshaft might you recommend?</a>&nbsp;-- <font color=#0000ff>giacamo, <i>04/10/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24507', contentMargin: 60, icon: $('anchor24507') }); </script>  RE: What camshaft might you recommend? -- giacamo, 04/10/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24511&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24511" onclick="return false;">Agree with Giacamo. N/M</a>&nbsp;-- <font color=#0000ff>Royce, <i>04/10/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24511', contentMargin: 60, icon: $('anchor24511') }); </script>  Agree with Giacamo. N/M -- Royce, 04/10/2005
 I can't convince him (dad) to change -- Greg Westphall, 04/10/2005
 RE: What camshaft might you recommend? -- rick, 04/20/2005
Collapse <b>CFM formula</b>&nbsp;-- <font color=#0000ff>Bob, <i>04/11/2005</i></font>CFM formula -- Bob, 04/11/2005
 Btw -- Bob, 04/11/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24536&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24536" onclick="return false;">That CFM formula is for 4V applications</a>&nbsp;-- <font color=#0000ff>Royce Peterson, <i>04/12/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24536', contentMargin: 60, icon: $('anchor24536') }); </script>  That CFM formula is for 4V applications -- Royce Peterson, 04/12/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24538&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24538" onclick="return false;">This formula is for any Carb Eng</a>&nbsp;-- <font color=#0000ff>Bob, <i>04/12/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24538', contentMargin: 60, icon: $('anchor24538') }); </script>  This formula is for any Carb Eng -- Bob, 04/12/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24539&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24539" onclick="return false;">RE: This formula is for any Carb Eng</a>&nbsp;-- <font color=#0000ff>Bob, <i>04/12/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24539', contentMargin: 60, icon: $('anchor24539') }); </script>  RE: This formula is for any Carb Eng -- Bob, 04/12/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24541&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24541" onclick="return false;">The formula provided is for a non compressible fl</a>&nbsp;-- <font color=#0000ff>Greg Westphall, <i>04/12/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24541', contentMargin: 60, icon: $('anchor24541') }); </script>  The formula provided is for a non compressible fl -- Greg Westphall, 04/12/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24542&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24542" onclick="return false;">Sometimes practical experience counts for more...</a>&nbsp;-- <font color=#0000ff>Gerry Proctor, <i>04/12/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24542', contentMargin: 60, icon: $('anchor24542') }); </script>  Sometimes practical experience counts for more... -- Gerry Proctor, 04/12/2005
 RE: Sometimes practical experience counts for more... -- Bob, 04/15/2005
 RE: Sometimes practical experience counts for more... -- walt, 04/16/2005
 RE: The formula provided is for a non compressible fl -- rick, 04/20/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24558&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24558" onclick="return false;">It sure doesn't work for an 8V 427.</a>&nbsp;-- <font color=#0000ff>Royce, <i>04/13/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24558', contentMargin: 60, icon: $('anchor24558') }); </script>  It sure doesn't work for an 8V 427. -- Royce, 04/13/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24560&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24560" onclick="return false;">Guess I am saying it wrong.....</a>&nbsp;-- <font color=#0000ff>Royce, <i>04/13/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24560', contentMargin: 60, icon: $('anchor24560') }); </script>  Guess I am saying it wrong..... -- Royce, 04/13/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24575&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24575" onclick="return false;">Gee, now you're responding crankily to yourself. :-) [n/m]</a>&nbsp;-- <font color=#0000ff>Mr F, <i>04/13/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24575', contentMargin: 60, icon: $('anchor24575') }); </script>  Gee, now you're responding crankily to yourself. :-) [n/m] -- Mr F, 04/13/2005
 Lol! n/m -- Royce, 04/14/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24587&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24587" onclick="return false;">RE: which carbs to use BJ/BK or BC/BD?</a>&nbsp;-- <font color=#0000ff>walt, <i>04/16/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24587', contentMargin: 60, icon: $('anchor24587') }); </script>  RE: which carbs to use BJ/BK or BC/BD? -- walt, 04/16/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24597&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24597" onclick="return false;">Not original camshaft, Oregon Cam Grinders</a>&nbsp;-- <font color=#0000ff>Greg Westphall, <i>04/16/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24597', contentMargin: 60, icon: $('anchor24597') }); </script>  Not original camshaft, Oregon Cam Grinders -- Greg Westphall, 04/16/2005
Collapse <a href=../ForumFE/reply.aspx?ID=24632&Reply=24488><img src=../images/reply.png width=30 height=10></a>&nbsp;<a href="#" id="anchor24632" onclick="return false;">.050 duration 6250-B & 6250-C Cams</a>&nbsp;-- <font color=#0000ff>Greg Westphall, <i>04/18/2005</i></font><script type="text/javascript"> new HelpBalloon({ dataURL: 'replyb.aspx?ID=24632', contentMargin: 60, icon: $('anchor24632') }); </script>  .050 duration 6250-B & 6250-C Cams -- Greg Westphall, 04/18/2005
 RE: .050 duration 6250-B & 6250-C Cams -- walt, 04/24/2005
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