Yes. And the factory BBD is rated at 190cfm by Carter’s two barrel vacuum specs. Two barrels are rated at a higher vacuum depression than four barrels. It’s actually a little worse than that because every carb manufacturer has its own set vacuum levels for two and four barrel vacuum. The reasoning at the time was that an engine would never be capable of producing the same level of vacuum with a four barrel as with a two barrel. However, in performance usage, while a two barrel will ultimately become restrictive at a point, any additional vacuum the engine creates above the carburetor rating makes the actual flow numbers much higher. Restrictor plates are some proof of this, as dyno testing with mass air flow sensors show a 390 cfm Holley on a super speedway engine will still pass well north of 700 cfm without the restrictor plate in place. This isn’t saying that a two barrel is going to be at the same performance level as four barrel, not by a long shot! But an engine will still tend to pull close to its air requirement at its peak as long as too large of a restriction isn’t in place. I think that for 75% of the \6’s out there, a large two barrel and two barrel intake will match the performance of a four barrel with four barrel intake without near the complexity, but mostly from benefit of a two barrel intake’s smaller plenum volume boosting the torque in the fat part of the curve of most \6 builds.
