I just went through this with my Rochesters and the thing you need to do is take the bases off and check the throttle plate seal with a light. Chances are they wont be any good. I ordered new secondary bases from Vintage Speed in Florida and it solved all my running problems, rough idle, irratic vacuum reading etc. I dont know anything about the Speedway bases but the people at Vintage Speed are super to talk to and the stuff he makes is beautiful precision parts. Google Vintage Speed and save yourself alot of trouble. His kit gives you two end bases, progressive linkage, new primary shaft and throttle blades, and jets for all three carbs and all the gaskets. His end bases are machined in his shop and are made with no idle circuits or idle screws.