Update to an very old thread. Moved from 3,500 feet to 8 feet above sea level. First did the obvious and took the primary and secondary jets up two sizes to the original that came with the carb (78 and 86).
Then I turned in all the idle screws and got it to idle a little lower, but I felt it had more to give. My new neighbour Percy is an old carb tuner and builder, working on sprint cars and the like for 40 years. Very nice guy with a shop full of Holley parts, a small machine shop, and a nice kit Cobra with a 347.
We moved the timing up to 26 degrees, brought the total timing back down to around 36, and it was much happier, vacuum is now consistently around 10 inches. Percy thought there was more there, and it was still suffering from a little too much run on, plus he had a manual choke kit for me. We pulled the carb and adjusted the throttle positions to close them a little more (what you need to run at 3,500 feet is not what runs well at sea level), replaced the power valve with a 5.5 (was a 6.5), and put in larger primary pump nozzle and it now hits harder at 2,000. Need to do a little cruise driving to see how it runs, WOT runs are fun but probably not the only thing to test. Run on seems to be minimal now, and the starter is not having trouble at 26 degrees advance. I won't bother with vacuum advance since I really don't care about fuel economy.
