We all know the formula for cfm rating:
Cubic inch * max rpm / 3456
So a 261 is rated about 377 cfm @ 5000 rpm right?
minus some VE let´s say 80% it is 300 cfm
Tom Langdon says in his catalog the Dual Offy Holley /Weber setup is the most streetable.
H/Ws are flow 250 each that would be close to 500 cfm for 2 (almost it is not linear) and a lot of poeple (including me) drive them, some even have 3 of them and are quite happy.
The litte Barry Grant 4 BArrel Road Demon flows 525 cfm and the manufactor website says:
"The new 525 Road Demon is for V6 engines and small V8s in the 260 to 400 cid range. "
WHAT?
Some guys even have TRIPLE WEBER 45 SIDE DRAUGHT CARBS on a 235 and swear that it is the most powerfull setup you can have.
Can we ignore the fact that all those combos flow way more than the 300 cfm? They seem to work fine.
Does the famous formula really work or is it rather a minimum than a maximum estimation?
On staged carbs with vacuum secondaries I would say thay flow what the engine can suck, but the Weber/Holleys or the Weber side droughts are ruled by foot.
Frank
