Holley 470 cfm.
Posting Guru
Joined: Jul 2015
Posts: 2,239
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From: Northeast Ohio USA
You had to know that debate would ensue...lol. All joking aside, anything under 550 cfm will suffice on a stock small block. My M2150, resting on My 302 with a manual choke has served well in the rust belt.
FTE Legend
Joined: Nov 2015
Posts: 30,912
Likes: 4,123
From: Angier, NC
Just want to point out to people that do not know carbs that well.
BTW you do know 2v carbs are flow tested differently for CFM than 4v carbs are so you cant really go by throttle bore size and call both the same CFM.
Dave ----
Junior User
Joined: Jul 2012
Posts: 90
Likes: 0
From: West Australia
Not being picky but the quoted CFM figures are not quite right.
The maximum volumetric efficiency will be at peak torque.
If we use a figure of 3200 RPM this engine will be using 327 CFM at peak torque.
As the RPM increases volumetric efficiency drops off, this is not from a restricted carb but a combination of port design, manifold, valve sizing cam design etc.
If you look at the figure used of 4627 rpm and a volumetric efficiency of say .8 then the carb only has to flow around 377 CFM.
Doubt this motor in standard form would ever out run the 470 carb.
The maximum volumetric efficiency will be at peak torque.
If we use a figure of 3200 RPM this engine will be using 327 CFM at peak torque.
As the RPM increases volumetric efficiency drops off, this is not from a restricted carb but a combination of port design, manifold, valve sizing cam design etc.
If you look at the figure used of 4627 rpm and a volumetric efficiency of say .8 then the carb only has to flow around 377 CFM.
Doubt this motor in standard form would ever out run the 470 carb.
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