I have asked this in the same time as other questions, but I have never felt that I have been given a convincing answer. This time I make a thread for it where all carburetor experts see it. I have been told that Holley makes every engine start and run, but not perform 100%. That it would be huge improvement if I change back to a Rochester. Lower fuel consumption, more power, less screws to adjust, or need to adjust at all. Just fantastic. Let's start there. Is this true? Sounds logic. A Rochester made for the engine should perform better, however, my Holley is made in modern times and should have some improvements over a Rochester made 47 years ago. Today I have the 770cfm Holley Street Avenger (80770-1). (LINK TO WEB) It works, but I want the best. Q: I notice that this one has vacuum secondaries. What have Rochester, vacuum or mechanic secondaries? What is good and bad? So I wonder: 1) If my Holley is a keeper. 2) Or should I get a stock 1968 Rochester. 3) Or get 1969-70 intake manifold and 1970-1974 Rochester. - And why one choice is better than the other. Some say that 800cfm is not necessary, but it don't seem to be negative? I have larger exhaust system, if anything break I would probably buy something more improved which I guess would appreciate more gas. Some say that the improvements are not doing much anyway, but they do something? Thanks.