[edwhite7]

If you feel the secondaries open then the carbs are most likely not set up correctly. Feeling the surge as the secondaries open usually means that the engine is not making enough power prior to their opening. If you plan to use the Snellings and Hellings air cleaners you may want to mill off the choke air horns so that the carb can breath. I have two 390's with mechanical secondaries and I like them a lot better than the 600 vacuums that I used to have. If you ask me on a cold morning I will tell you their perfect but on many hot summer days I get a flat spot at about 1500 RPM as I get on the gas. It is a work in progress.