ok i am getting pretty in depth and trying to learn more. i have an 850 cfm carb. i know that a 4bbl carb is rated at 1.5hg. but what i dont understand is how ppl figure out how much cfm is acually flowing. i know there are calculations that involve (inhg) and (inh20). and how do i find my pressure drop? will a vacuum guage tell me what i need to know for pressure drop and if so does the engine need to be under load or free rev. and how could you estimate the amount of air restriced by an air cleaner. if anyone has any ideas or can help me with anything plz lmk