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Old 11-16-2012, 04:54 PM
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Holley 650 HP flow numbers

Anyone have any idea how much CFM a Holley 650 HP flows out of the box?

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Old 11-19-2012, 07:40 AM
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Originally Posted by Richiehd View Post
Anyone have any idea how much CFM a Holley 650 HP flows out of the box?

think you answered your own question
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Old 11-19-2012, 08:21 AM
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Originally Posted by gearheadslife View Post
think you answered your own question
the "650" is a label, not a flow measurement, none of the holley's flow what their label is, all the basic holleys are under and the HP's are a little over.

It'd be neat to see a spreadsheet of all of the common carbs on a flow bench, I think people would be really surprised by what some of them really flow.
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Old 11-19-2012, 08:31 AM
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Originally Posted by ap72 View Post
the "650" is a label, not a flow measurement, none of the holley's flow what their label is, all the basic holleys are under and the HP's are a little over.

It'd be neat to see a spreadsheet of all of the common carbs on a flow bench, I think people would be really surprised by what some of them really flow.
correct me if I'm wrong.. but I'd think a 650 cfm car that didn't flow that or at least -1% or 650+ would be false advertising
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Old 11-19-2012, 09:33 AM
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My actual 650 was on a flow bench.It flowed 641 and after installing an 850 base plate it flowed 773cfm,,,now how do we know the flow bench is accurate?a different flow bench might offer different numbers.
What I cared about was improvement,or increases
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Old 11-19-2012, 09:57 AM
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Originally Posted by gearheadslife View Post
correct me if I'm wrong.. but I'd think a 650 cfm car that didn't flow that or at least -1% or 650+ would be false advertising
You would be wrong as Holley doesn't promise any particular flow, its just a label. They're not the only ones that do it either- most carb companies do. From what I recall Demon carb's are actually better than their label would indicate though (I think they're the only "non race" carb that is).
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Old 11-19-2012, 11:01 AM
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Originally Posted by vinniekq2 View Post
My actual 650 was on a flow bench.It flowed 641 and after installing an 850 base plate it flowed 773cfm,,,now how do we know the flow bench is accurate?a different flow bench might offer different numbers.
What I cared about was improvement,or increases
I agree! Heres a little adition vinnie

Years ago the Society of Automotive Engineers provided a standard for Airflow that's still used today. For 4-barrel carburetors that number is measured airflow at 1.5" pressure drop, or used on a flowbench is 20.4" water. For example a 750cfm carburetor should flow 750 (cubic feet per minute) at this pressure drop. A carburetor has fuel flowing through it which actually displaces some airflow (usually around 8%), so this should actually be flowed with fuel or wet flowed. Tests are not absolute but averages not including, temp, atmospheric pressure, temp, or engine efficiancy

Jester

Last edited by painted jester; 11-19-2012 at 11:14 AM.
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Old 11-19-2012, 11:12 AM
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Your engine needs X amount of airflow to reach a certain power level efficiently. The formula for CFM consumed is (CFM = CID x RPM x VE 3456). Here CID = Cubic Inches; & VE = Volumetric Efficiency. This is just a rough estimate as VE number is the basic efficiency or cylinder filling of the engine. Let's take a typical small block chevy 383ci stroker engine at 6500 rpm assuming 100% VE. Plug in the numbers & you get a CFM requirement of 720. Street motors might be 90% & a good race engine might be 125% with a single carb! But put on a tunnel ram or a high rise race intake and cfm climbs drasticly because of the velocity of the ram effect aiding the engines ability to flow more air !! throwing that formula out the window

I thought this might help

Jester
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Old 11-19-2012, 06:49 PM
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OK< I got some interesting answers, kind of what I expected. My question was posted because I know a Holley 650 is advertised as flowing 650 cfm, we all agree on that. However, the HP, not the Street HP, should by theory flow more, because of modifications and polishing of the veturies. I wondered if anyone had actually seen any numbers. Im running 355, World Heads, solid lifter cam and wet exhaust on my 16 foot Jersey Skiff. We can turn 7000 no problem, and the mid range creates awesome acceleration. I was thinking of going to bigger carb but would hate to lose the midrange.
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Old 11-19-2012, 07:04 PM
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you could use an out of the box 850
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Old 11-19-2012, 07:16 PM
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I agree

Jester
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Old 11-19-2012, 07:37 PM
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Quote:
Originally Posted by Richiehd View Post
OK< I got some interesting answers, kind of what I expected. My question was posted because I know a Holley 650 is advertised as flowing 650 cfm, we all agree on that. However, the HP, not the Street HP, should by theory flow more, because of modifications and polishing of the veturies. I wondered if anyone had actually seen any numbers. Im running 355, World Heads, solid lifter cam and wet exhaust on my 16 foot Jersey Skiff. We can turn 7000 no problem, and the mid range creates awesome acceleration. I was thinking of going to bigger carb but would hate to lose the midrange.
properly built and tuned a bigger carb will NEVER cause a loss of power in the mid range or even off idle.

That old wives tale comes from people who can't build and tune carbs.
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Old 11-19-2012, 08:41 PM
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As always, thanks for the input. I may step up to a 750. Tunnel ram is out, if you knew the type of skiff you would see why. Besides it wouldn't fit under the hood!!
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Old 11-19-2012, 09:03 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
You need significant engine horsepower increases to see a gain in boat speed , on the water.
The tunnel ram works very well on boats and will make the most power on your motor.
But do not make the mistake of choking it with tiny carbs. Use two 650's or two 750's
on it. Two 750 edelbrocks would be cool.
A cross ram would fit under the hood!

Jester
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Old 11-20-2012, 01:14 AM
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properly built and tuned a bigger carb will NEVER cause a loss of power in the mid range or even off idle.

That old wives tale comes from people who can't build and tune carbs.



thats just silly.. if that had any truth to it, all the carb based engines at engine masters would have the biggest honk'n dominator on top..
they don't
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