Originally posted by SBC Maro
What exactly does port volume effect?
Port volume affects the velocity of the fuel/air mixture. A small volume figure will work great on the vast majority of OEM motors that haul grandma to the bingo hall, but when us hot rodders get hold of the motor, we want to rev the motor higher to get more horsepower out of it, so we replace the small port heads and small port intake manifolds with ones which are larger and will flow more mixture at higher rpm's. Just as with everything else in life, there is a limit to the volume which you can effectively use in a street motor. Heads with 230 cc's of volume might work great on a race motor that sees 7,500 to 8,000 rpm's, but they would be too large to maintain any sort of velocity to pack the cylinders on a motor that would only see....maybe....5,000 rpm's max. Consensus of opinion seems to dictate that somewhere between 170 and 195 cc's will be optimum for a street motor, leaning heavily toward 170 if you want to be realistic.