rods and mains have nothing to do with cfm flow.
And the rated flow is just a rating.
You could theoretically install that 285 cfm carb on a lawnmower and and it will never get past what that measely lawnmower can pull. OR you could install that 285 on a 400 cubic inch engine and pull a lot more thru it than 285.
So the carb manufacturers figured out a scientific way to rate them by pulling air thru them at a standard pressure differential,and a standard temperature and measuring the cfm flow.
But not every manufacturer uses the same test method, and 2bbls are tested differently than 4bbls. And there are formulas to "reconcile" the different methods.
Finally. if your engine can only pull 220cfm on the test machine, then it will not make any more power using a 285. The common formula for estimating the amount of air your engine can ingest is;
rpm x cid/3456; where cid is cubic inch displacement. The Formula is for an engine that is able to ingest this air at 100% Volumetric Efficiency so you have to down-calculate to your Efficiency.
Ok so
(225 x4500) /3450 =293 cfm and if your 225 manages a VE of .75, then
293 x.75VE = 220cfm. Now, your engine will a different VE at every different rpm you test it at so the .75VE I chose might be the best she can do in stock trim.
Can your slanty pull more than 220cfm, well maybe, at a higher VE or at a higher rpm. Say you bumped the compression up and installed a free-flowing exhaust and a cam that works to 5200. Now your numbers could be
(225 x 5200) /3450 x .84 =285 cfm
But say you never go over 4000,
and your 225 is well used; then
225 x 4000/3450 x .65VE =175cfm
Finally, if the 285 fits on your intake, just bolt it on and see what happens. I bet it will be just fine, if a lil sluggish on the get-go.
But do not attempt to swap the guts,from one carb to another; that is a recipe for disaster.
But say you had a fresh 318;
318 x4400/3450 x .70VE= 285cfm
Can the 318 pull more than 285?
Well sure, just like yours. But just cuz the carb is rated at 285 does not mean that it cannot pull any more thru it; remember that 285 is just a rating at a certain pressure differential. Nothing changes at 286 cfm, nor 290 or even 300 .... except the pressure differential, which is measured as Vacuum inside the intake manifold.
BTW-1
as to the damage on the venturi, those brass parts you see there may have a tiny hole on the top which has to remain open and correctly sized for the circuits to work properly. But the venturi doesn't much care about anything else, as long as it ain't broke. If they are tubes sticking up, that is for to get them up out of turbulent air. You can get brass-tubes at the model-airplane store and rig something up, just make sure that when yur done, it won't ever fall into the engine,lol