1 Bad Mirada

i do not know for sure, but a correctly tuned carb system will be no more or less efficient depending on the exact setup. I do not recall the exact CFM measures of the primary and secondaries of the "six packs", but figure that if you have a 300CFM primary, and twin 175 secondaries, you have 650CFM. I am using that number because thats what I ran originally on the mirada when my 340 was near stock. compare that six pack, properly tuned, to a 650 CFM 4bbl carb. they can both take in the same amount of air, so as long as they are both properly tuned, they should, in theory, use the same amount of fuel to achieve the optimum air to fuel ratio of around 14 to 1...

i would think that the six pack would also give you the option of dumping alot more fuel and air in at higher rpms when the secondaries open, which are only ideally open when youre under moderate to hard acceleration. when i want to change the size of my secondaries on the mirada, i have to change the entire carb, and in most cases the primaries are relatively a similar size to that of the secondaries. however, if you want alot more air and fuel at high rpm, it would seem to me that the secondaries could be changed, and tuned so that when they open, they would dump alot more air and fuel in...that would eat up alot more gas, but overall, a stock or evenly modified six pack shouldnt be any more inefficient than a 4 bbl carb...

again, ive not dealt with one, so if someone can correct me, feel free!