best cfm for a stock 305?

[bean]

Is a 600 cfm best recommendation for a stock 305? Thinking about going from stock q jet to an edelbrock. .. any feedback is appreciated

[stomper]

I had a 500 cfm edelbrock on a hot 283 once. It was snappy. The advantage of that small carb was increased intake velocity. A common mistake is to go too big and it's sluggish on throttle response. I'm sure there are formulas out there for you.

[bean]

That's my concern is going too big

[wreckedchevy]

I'm running a edelbrock 600 on my 305 the motor does have bigger cam and 202 heads on it ran ok with stock jetting but just got it jetted properly this summer and it runs outstanding now.

[mechanicalman]

Originally Posted by bean

Is a 600 cfm best recommendation for a stock 305? Thinking about going from stock q jet to an edelbrock. .. any feedback is appreciated

First of all, what kind of problems are you having, if any? I can expand on my comments if you tell me what is going on. Plus, I need to know if you have the original style quadrajet (divorced choke) or the later model style with round choke housing, again, to expand my comments.

Stomper is right, larger than necessary carburetors exhibit lower velocity than properly sized carbs.

Therefore, you should either keep your quadrajet or fix it. Quadrajet's have the smallest primary butterflies of any 4 barrel V-8 carb I've ever seen and appropriate venturis.

Quadrajet's were used from the factory on many engines including V-6's. They have an adjustable secondary air valve that allows the use of any engine that the primaries are not too big for, only allowing the secondaries to open as far as the engine demands them to.

For instance, Quadrajet # 1904 is designed for 305-350 engines.
http://www.summitracing.com/parts/edl-1904

To answer your question, as a general rule, 600 CFM a little big for a stock 305, I'd go with a 500 CFM Edelbrock.

[ssxty8]

A nice 305 can't consume all the performance a 600 vacuum secondaries can offer. I tell you cause that's all I have on my mildly modified 350, and it runs flawlessly. A 600 or 650 can supply enough gas/power up to around 400 HP; some people just want the bragging rights of 750+ CFM carburetors.
Oh, this is JMHO
Merry Christmass to ALL.

[bean]

Right now using the q jet off my original 359. It has the choke still on the side but no place in the manifold for it. Using that for the meantime

[bean]

It's completely stock just wanting a good running truck for back and forth to work

[71K20chevy]

The formula for finding CFM is CIDxMAX RPM/3456

305 x 4000(how often will the engine ever go past 4k RPM?)/3456=353

Obviously carbs that small aren't very plentiful, so something pretty small (500 cfm or under) would work fine.

That said, I'd keep the QJet, they really are great because the small primaries allow for great throttle response but the larger secondaries open up only when you need them, so you can have great drivability and gas mileage while still being reliable...that is if it's tuned right. Can't stress enough how important that is, I'm a firm believer in the Qjet myself, because they really are great when everything is set up correctly.

Just my 2c.