Factory Q-Jet CFM Rating? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**70cst** · 03-25-2002, 06:29 PM

What was the cfm rating on the factory Rochester carburetor that was used on a 402BB?
Thanks,
Dewayne 70cst

Project1970 · 03-25-2002, 06:56 PM

I'm pretty sure it's a 750CFM. I think all 4bbl V8s got the same Quadrajet, right? Mine's only a 350...

The Edelbrock #1901, which is a clone of the original carb I had on there, is definitely 750CFM, and the two look too close to be far off in CFM.

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Project 1970 - soon to be seen at http://milhouse.treylis.org:81/

69 longhorn · 03-25-2002, 07:01 PM

There was a 750 cfm,& a 795 cfm Q jet.....I cant say for sure,but the big Buicks & Olds used the 795 cmf carb........69 longhorn.

loenuf · 03-25-2002, 07:13 PM

bb and sb q-jets are different, sb are 600 cfm and the bb are 750 i think....

**70cst** · 03-25-2002, 07:20 PM

Thanks Guys...
My carb is beyong repair so I'm going to replace it so I wanted to be sure I had a similiar rated carb. I'm not sure which carb I'm going with but looking at Holley Avenger 770cfm or the Edelbrock.
Dewayne 70cst

**PICKMUP** · 03-26-2002, 02:41 AM

You are right, as usual, Longhorn. 750 & 795 or 800, but who's counting. When you look down inside the big one (maybe 455 Buick) the venturies are physically bigger.

Blazer1970 · 03-26-2002, 09:37 AM

The QJets referred to a 750 and 795 cfm are the same carb. There is an 800 or 850 cfm version (can't remember which), but it was never used on any truck motors. They were mostly used on the larger displacement Pontiac and Cadillac engines.

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Tim

03-25-2002, 06:56 PM	#2
Project1970 14.1 @ 96MPH Join Date: Jul 2001 Location: Mesa, AZ Posts: 2,811	I'm pretty sure it's a 750CFM. I think all 4bbl V8s got the same Quadrajet, right? Mine's only a 350... The Edelbrock #1901, which is a clone of the original carb I had on there, is definitely 750CFM, and the two look too close to be far off in CFM. ------------------ Project 1970 - soon to be seen at http://milhouse.treylis.org:81/ __________________ Project1970 - LS1 Swap Complete!

03-25-2002, 07:01 PM	#3
69 longhorn Registered User Join Date: Aug 2001 Location: rock island,il,usa Posts: 5,382	There was a 750 cfm,& a 795 cfm Q jet.....I cant say for sure,but the big Buicks & Olds used the 795 cmf carb........69 longhorn. __________________ http://community.webshots.com/user/hotrodhorn

03-25-2002, 07:20 PM	#5
70cst Senior Member Join Date: Feb 2001 Location: New Madison, Ohio Posts: 21,373	Thanks Guys... My carb is beyong repair so I'm going to replace it so I wanted to be sure I had a similiar rated carb. I'm not sure which carb I'm going with but looking at Holley Avenger 770cfm or the Edelbrock. Dewayne 70cst __________________ A husband can be right...or...A husband can be happy. 67-72 Chevy and GMC Trucks...The Classic Truck for the Classic Folk. 1970 CST Two tone green, 402BB, 400 Automatic, Tach, Buckets, AC, AM-FM, Tilt, GM CB, GM 8 Tract, LWB, etc JOHN 17:3...The better side of "LIFE" Remember: Everyday is a good day...Some are just gooder!

03-26-2002, 02:41 AM	#6
PICKMUP "Trucks with Class" Join Date: Jul 2000 Location: OLYMPIA, WA, USA Posts: 8,158	You are right, as usual, Longhorn. 750 & 795 or 800, but who's counting. When you look down inside the big one (maybe 455 Buick) the venturies are physically bigger. __________________ Email: frankeham@comcast.net Phone: 360-956-7170

03-26-2002, 09:37 AM	#7
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,507	The QJets referred to a 750 and 795 cfm are the same carb. There is an 800 or 850 cfm version (can't remember which), but it was never used on any truck motors. They were mostly used on the larger displacement Pontiac and Cadillac engines. ------------------ Tim __________________ Tim

03-25-2002, 06:29 PM	#1
70cst Senior Member Join Date: Feb 2001 Location: New Madison, Ohio Posts: 21,373	Factory Q-Jet CFM Rating? What was the cfm rating on the factory Rochester carburetor that was used on a 402BB? Thanks, Dewayne 70cst __________________ A husband can be right...or...A husband can be happy. 67-72 Chevy and GMC Trucks...The Classic Truck for the Classic Folk. 1970 CST Two tone green, 402BB, 400 Automatic, Tach, Buckets, AC, AM-FM, Tilt, GM CB, GM 8 Tract, LWB, etc JOHN 17:3...The better side of "LIFE" Remember: Everyday is a good day...Some are just gooder!

03-25-2002, 07:13 PM	#4
loenuf Registered User Join Date: May 2000 Location: trenton texas usa Posts: 232	bb and sb q-jets are different, sb are 600 cfm and the bb are 750 i think....



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