Is there a formula or some method (other than actually trying different carbs.) of determining what size carb. cfm would be best suited for your engine based on how your engine is built?

If its just for racing then think big.. I had
a 405ci and had a 1050 dom on it and wanted
to put a 1150 on it but sold the engine

Never mind

It depends on a bunch of things but for the typical engine you need the carb CFM rating to be about 1.40 times the engine horsepower. So 500 hp uses 700 cfm, 600 hp uses 840 cfm, etc.

I'll attach a worksheet that shows some of the variables.

If your racing it or looking for the most power and torque on the engine dyno sheets, bigger is better
The difference in head flow, cam LSA, actual rocker ratio and other parts have a direct effect on the engines ability to consume and use the air and fuel the carb allows into them
If your after the best mileage and street performance then think small primaries on the carb.
Years ago I did some carb size testing at the track on a 440 bracket race motor with a set of mild 906 iron heads and a big solid roller SS cam, it ran faster and quicker ET with the biggest carbs and intake I could put on it, I had assumed that by using a Holley 600 D.P. the car would 60 ft. better and get better reaction times and 60 ft. better, it didn't Every time I put a bigger carb . on the same intake it went faster and quicker
Theory and results are not always the same

Most formulas to determine correct size use rpm and cubic inch.
That said it generally isnt accurate.
I have found bigger is always better in a race car application.
I had a hot 318 motor that ran a tenth better with a 950 than it did with two different 750’s i tried on it, as an example

It also makes a difference if you are using a trans brake..
if you are then use a little smaller carb and the car will
leave better off the line due to lower RPMs

Several factors come into play for ME personally, street or strip or BOTH.
Heads, fuel,cam,converter, gears,shift points, weight altitude etc........I'm one of the few who never use a calculator to determine these things and I do real world street and track testing so the COMBO tells me what carb will work best for that application............

Not sure what you mean
When i used a brake i had 2 step set at 4300
Off foot i left at 2k, so way lower
Car 60 footed identically either way( as it should)

i don't get lost in cfm ratings and don't use them as a major criteria for carb(s) selection. i'm old school and still look at venturi area.

I'd like to get the best mileage I can. I know that in speaking of muscle cars, mileage is usually not a concern but I am not concerned with how fast I can go anymore. I'm planning on changing the rear gear to a 3.23 from the current 3.91 that is in it and thought a smaller carb. would help as well as long as it won't affect how well the engine runs (not speedwise but just general operating performance). What I have is a pretty much stock 67 440 HP engine except that when the previous owner rebuilt it, he installed lower compression pistons. I don't know exactly what the ratio is but I think it is about 9:1 or thereabouts based on what he told me. The engine currently has a 750 Edelbrock 1411 carb on it and I'd like to replace it with a lower cfm carb. if possible. Would a carb in the 600-650 cfm range be enough carburation or would that be too small for my 440?

Some people get confused over how much air the engine needs and how big the carb should be. If you know how much power the engine is going to make then you can calculate how much air the engine will consume to make that power. For example, a 600 hp engine will consume roughly 850 cfm of air at peak power. So that is the easy part, the harder decision is what size carb to buy. Obviously a 850 carb would work but so would a 650, 750, 950 or 1050. The different carbs will work differently with the smaller carbs working better at low speeds while the bigger ones are better at WOT.

So the answer is "it depends" which is the same answer to most of the questions on here. You would need to provide some specifics on the car and engine and how you are planning to use it to get a better answer.

For your application the 750 would work but a slightly smaller carb might work even better. The factory used 600 cfm carbs on a lot of 440 engines. A 400 hp engine only uses 560 cfm at peak power so a 600 cfm carb works just fine on a street driven 440. 90% of street driving is at part throttle anyway.

But they can be if you know, for sure, what the engine's volumetric efficiency is. It is possible for a normally aspirated engine to attain better than 100% volumetric efficiency.

If you’re looking for better economy, try the new Edelbrock avs2 650 or one of the Street Demons.

I’m not sure how much better the mileage would have to be to justify buying a new carb, but imo if it improved the mileage by 1-2mpg....... you’d be doing pretty good.

the edelbrock 750 is identical to the stock '67 hipo 440 carb in throttle bore size and venturi. I've been playing with one on my stock 440, 9.3:1 compression. with the 750's velocity controlled secondaries I believe you could do a lot worse and waste money on something that's not any better.

On your deal I would look at a Thermoquad or Quadrajet type carb. to get the small primaries with the larger CFM rating at WOT, you will need the correct intake manifold(stock 1972 and later 440 intake ) or a carb to manifold adapter
Sometimes you have to think and act out of the standard box

625cfm or 750cfm. Either one will work for OP.

https://www.youtube.com/watch?v=YNAlVFtUFL4

https://www.youtube.com/watch?v=DPOuEOkazVc

https://www.youtube.com/watch?v=IHWJpZCmUAk&t=10s

https://www.youtube.com/watch?v=oAhdCRixqqw

This.

I have an 800 CFM Holley spreadbore carb on a factory cast iron intake that is my go to combo. The carb has been attached to the intake for the last 25 years and I use it on my stuff or loan it our for others to use because it runs so beautifully on stockish 440s. Then I wrap it back up and put it back into storage until the next guy needs it. Throttle response is great, mileage is better, and power is as good as anything except a 6 bbl.

So how much would a 1.48 venturi 1.79 throttle blade carb support..... asking for a friend