340 intake on a 318?

comparing replacing a 318 2bbl manifold with a 340 4bbl is comparing apples and rutabagas. Sure the 4 bbl will perform better compared with those tiny 2 barrels. The right comparison is between that mismatched combo with a 4bbl manifold with small ports that match. You should be able to get a used Edelbrock Performer manifold for $100 or less with the small ports. Most Weiand small block manifolds come with the smaller ports (you can enlarge the port to match 340 or 360 ports). The turbulence cause by the charge hitting the lip around the head ports can't help but disrupt the flow. For an extra $50 why not do it right?