I ordered a new Edelbrock RPM Air Gap Manifold and received it a few days ago. It's going in my '71 RS 355 with a 650 DFDP. It's running pretty good now and I have a 2" Spacer under it (an improvement). The new manifold is 1" taller than the single plane Holly Street Dominator from the 70's that's coming off. So I ordered a new 1" spacer to test. I placed it on there and the main plenum ports do not line up with the spacer! Quality control? If I had just bolted it on and then mounted a carb to it I may have never known! I measured from the stud centers to the plenum opening on each side and and it's off by at least 3/16!". That's not good as it creates a step the flow will bounce off. You can see it in both the 2nd and 3rd picts. I have no idea how many manifolds/brands are defective in this area.. something I will now check every time. Summit was awesome - they did not even want to see the picts and another manifold will be here in a few days. I wonder how many of these are running down the street? This looks bad as the two rights ports are cut off. This is how a carb will line up. Here one side is overlapping the plenum opening and the other has a step in the flow path. This is on it now..