Re: difference between 2bbl cabureters and 4 bbl carbureters
S1jor, depends on how how you mean it. I'll assume that you know the obvious. (4 air/fuel entry passages vs 2). As a general statement, 4 bbl carbs have the ability to allow a higher volume of air and fuel to enter the combustion chambers of the engine and to do so with more versatility. 4bbl's have a pair of primary ports and a pair of secondary ports that are usually opened sequentially by either mechanical linkage or by the drop of vacuum caused by some degree of throttle activation. In essence a 4bbl can deliver a more infinite range of fuel/air to the the engine from idle to full throttle.<br /><br />However, all engines would not necessarily benefit from a 4bbl carb. All carbs (rated in cubic feet per minute flow) need to be matched to your engines ability to move air thru itself via the displacement, compression, valve sizes and intake and exhaust passageways. Ususally it is higher performance engines that gain the most power from using a 4 bbl carb while allowing a higher level of economy at lower power demand by using only the primary ports.
