1984 Trans AM 305v8 stock carb # 17984280 manufactured May 1984. What is the cfm of this carb? Perhaps 650.

 

A quadrajet carb CAN flow up to 800 cfm.
Don't panic, it's not too large for a 305. The factory used them on 6 cylinder engines also.
Because of the spring-loaded secondary air valve, the carb will only flow as much as the engine demands.

 

As I recall there's only 2 different sizes to quadra jets. 750 and 800. I can't be 100% certain but all ccc qjets were 750.

 

NoEmissions84TA is correct in that the Vacuum-Secondaries of the Rochester will only ever open enough to meet the Engines demand.
This is the only benefit of a Vacuum-Secondary Carb, in my opinion.

 

If it's a Q-Jet, wrong question to ask.

It's the EXACT RIGHT CFM, no matter what that is, for any engine from the 300 inch range up to 500 or so, with little or no modification. After all, it's a QUADRA-JET.

What question should you have asked instead? What is it you REALLY want to know? Which Edelcrap Carter knockoff you should hack onto it so you can further devalue your car? (not to be harsh or anything, I'm restraining myself from saying what I REALLY think)

 

Unbelievable that a 305 ci can handle a 750. Actually, I think that is amazing about the QJ.
I had a '72 Buick gs & it had a 750 cfm carb. The 455 engine had an 800 cfm.
My first car, a 1970 Mabilu L48 engine had a 750 carb.
Never own a Edelbrock.
I will stay with the QJ but will have have it rebuilt the winter.

 

Don't worry about "unbelievable". BELIEVE IT. It IS what it IS.

Why are you even asking this thing? Instead of asking how to kill the alligators, tell us what trouble you're having building the bridge. Don't even bother with talking about your trouble with draining the swamp. Start at the end objective and work BACKWARDS, instead of getting some assumption in your head about where to start and trying to work FORWARD. That's a guaranteed FAIL.