4 barrel cfm

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Sep 28, 2015 | 01:56 PM

Bobby455

Thread Starter

Registered User

Joined: May 2015

Posts: 171

From: East Hartford, CT

4 barrel cfm

I have a 71 350 with a 4 barrel, stock, came with the car, never been changed. I'm wondering if anyone knows what the cfm rating for this carburetor is? I looked it up and one article said 750 cfm but I really don't think that's right

Sep 28, 2015 | 04:11 PM

Fun71

Registered User

Joined: Feb 2013

Posts: 15,310

From: Phoenix, AZ

Yes, that is right. QuadraJets are vacuum secondary carburetors so they flow only what the engine demands, up to their maximum flow capability, which in this case is 750 cfm.

Sep 28, 2015 | 06:23 PM

MDchanic

Connoisseur d'Junque

Joined: Sep 2010

Posts: 21,183

From: The Hudson Valley

Quote:

Originally Posted by Bobby455

... one article said 750 cfm but I really don't think that's right

Why not?

- Eric

Sep 29, 2015 | 05:38 AM

joe_padavano

Old(s) Fart

Joined: Mar 2007

Posts: 50,539

From: Northern VA

Quote:

Originally Posted by Bobby455

Keep in mind that the secondary air valves on the Qjet only open as needed in response to mass airflow needs. The carb "self regulates" it's CFM rating to match the needs of the engine. On smaller motors (like the 307s), the secondary air valves are actually restricted by a stop so they only open about 70 degrees instead of the full 90 degrees.