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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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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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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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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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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
:thumbup: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
 

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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:D

I thought this might help

Jester
 

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Discussion Starter · #9 ·
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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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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Discussion Starter · #13 ·
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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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!:mwink:

Jester
 

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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.

:nono:

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 :drunk:
 

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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.

:nono:

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 :drunk:
 

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Thats not silly its true you might not gain any horsepower from the bigger carb unless you needed more carb in the first place but tuned and built right you will not lose any either one reasons why they dont all have bigger carbs is cost have you prices one them big honkin dominator lately and whos going pay all that money if you not gaining a lot of hp not me
 

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Thats not silly its true you might not gain any horsepower from the bigger carb unless you needed more carb in the first place but tuned and built right you will not lose any either one reasons why they dont all have bigger carbs is cost have you prices one them big honkin dominator lately and whos going pay all that money if you not gaining a lot of hp not me
sorry signal strenth goes out the window.. if you want only peak hp..
then I'd guess it might be right..
some like having a powerplant that doesn't cough and fart untill 2500rpm+
and those pro's at engine masters the cost of a dominator is peanuts..
 

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sorry signal strenth goes out the window.. if you want only peak hp..
then I'd guess it might be right..
some like having a powerplant that doesn't cough and fart untill 2500rpm+
and those pro's at engine masters the cost of a dominator is peanuts..
The signal strength is more than adequate if you know what you're doing- again most people just don't know what they're doing.

As for Engine Masters- the carbs are restricted by the rules.
 
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