Read the Mopar Direct Connection engine book
I can't remember but think it was to add a little top end--dual Planes are under rated folks think they will not make HP like a single and that is mostly correct but the TQ down low that is given away with a single plane is considerable
I always relate this tale--while at Indy Cylinder head one PRI week Herb McCandless brought a high compression giant roller 360 CI aluminum rod for dyno test with the then in development Indybrocks--it made a little over 600 HP with single plane but still managed over 584 HP with an air gap dual plane--I raced 1/8th all my life and always had a dual plane RPM or such with maybe a spacer
Most LD 340's you find these days are cut down center divider because the Mopar book said do it It will not hurt the intake
