A simplified way to think of it is that each component in the flow tract is a resistance. The total flow capability is related to the total resistance of all the components added up. The flow measurement for each component is an indication of it's relative resistance, not an absolute limit. So, reducing the resistance of one component, like an intake, still reduces the total resistance, even if the measured value for that component is not the lowest resistance (highest flow) in the system. The total flow is based on the sum of the components, not the smallest measured value within the system. This ignores the FM effect, where adding two components results in better performance than either alone would indicate.

(FM = F****** Magic)

'Any sufficiently advanced technology is indistinguishable from magic.'
Arthur C. Clarke

 

even though the intake knocked the flow down 20-35 cfm and made a 289 cfm head flow 263 @ 28", placing the intake on a head that flows 263 cfm with no intake will not get you the same 263 cfm with the intake. You are still gonna lose 20-30 cfm by sucking through the intake also.

You just start off higher and end up higher even after installing the intake with the better flowing head.

The next thing is that the engine will see air moving MUCH faster than a 28" flow test and the flow lost will be even more dramatic.

The engine also sees the air in gulps instead of a steady suction. This is where key areas need to be certain sizes to feed the engine and that might not show up on a flow bench @ 28".

A head flowing this well @ 28" (over 280 CFM and not leveling off at .550 or even .600) will usually be shaped correctly and measurements in key areas to feed the engine better where as a 250-260 cfm head will probably not have these things. If the porter was trying hard or had the knowledge, why would they only end up @ 250-260 cfm?

 

Well i think budget is the reason why . Well that is some good info you and Bret posted thanks.