I,v been trying to locate stock exhaust manifolds for my 70 Duster....Motor is a mildly warmed up 318 and I don,t want the hassle of headers, mainly because of the heat soak troubles with the starter and on the left side,the tie rod passes through header pipes. I have a right side {Passenger} manifold that is casting #3418623...fits a 340 motor from 1971-1973.Left side I have 2 manifolds, 1st one is casting #3614395....fits a 318-1972-1973 Dart.2nd one is casting #2951123..fits a 318-1968-1969 Dart.The dilemma I have and this may sound like a dumb question is.....the right side 340 manifold is 1 and 7/8 inch inside diameter at the exhaust exit.The left side manifolds..both of them are 1 and 5/8 inch inside diameter at the exhaust exit.With a 1/4 inch difference exit diameters,would this adversely effect performance of the motor????? in addition to making exhaust pipes bolt up to the flanges on the manifold.the bolt centers on the 2 manifolds from side to side are 1/4 inch different also.. 3 and 3/4 for the right side versus 3 and 1/2 for the left side.Also, the left side manifolds "Swoop" up a bit before going back down....Information I have is I need either manifold casting # 2863553 for a 340 motor or manifold casting #2843953 for a 318 Dart...I,m thinking I need 2 matched pairs of manifolds with equal exhaust diameter exits...
Last edited by DusterJeff; 06/23/15 01:06 AM.