cfm/s on carbs, was TQ carb question

[dardal@xxxxxxxxxxxxxxx]

The statement that "over-carbing" an engine can lead to driveability problems 
is correct.  However, I am lately leaning towards the idea that the simple 
equation used to estimate the 550 cfm for the 440 at 5000 rpm may not be 
entrirely correct.  The reason I believe that is that the equation assumes 
steady state flow though the carburetor.  In reality, the flow is pulsed, and 
even though the average flow at say 5000 rpm may be close to 550 cfm, the 
instanteneous flow may be higher, inducing a pressure drop that reduces 
torque.  I tend to believe that by observing my two 440's.  Even though the one 
on the green Sedan seems to have a larger cam than the one on my black LeBaron, 
the upper end difference is not as high as I would expect.  I think that the 
AVS on the green car (even though very reliable) may be giving some restriction 
at over 4500 rpm (I think this carb is about 600-650 cfm, so based on the simle 
equation its sufficient).  The black car has the q-jet of higher cfm.  Now, all 
that is not scientifically established or anything, its just from the seat of 
the pants.

True, most Imperials (413's and 440's) have the tiny stock cams which restrict 
usefull rpm to no more than 4500, and most have single exhaust that may 
restrict the useful rpm even more (at any rate, if you rely on the automatic 
shifting, the torqueflite rarely shifts over 4200 rpm).  So, I agree with 
Kerryp, for most IML'ers, 550 cfm is probably very sufficient.  For small 
blocks, even smaller carbs will suffice.  But if one mamaged to install a super 
big carb on a rather small engine without driveability and economy problems, 
good for you.  Just don't expect any performance improvements.

As to how often I reach 5000 rpm?  Well, not as often as I would like.  Too 
much traffic.  Fortunately, as the economy of Texas is going down hill, there 
are fewer cops out there ! ;)
D^2