Well been working on my 65 fastback for awhile and finally got it running right today - Edelbrock heads/cam kit, JBA headers, 2 1/2 exhaust, e-fan with variable speed thermostat controller etc etc - anyway when trying to get it running for the cam break in would only rev over 2K and then sounded fairly good but anything below stumlbled and quit. Got through the break in interval OK but spent forever trying to understand why it would not idle - dizzy off? firing order? cam a tooth off? on and on it went while it seemed like I had a huge vacuum leak but could not find it. Tried another carb, no help. Finally figured must have an intake major gasket foul up, was thinking of taking it off to recheck, had my finger along the drivers side intake runner just behind the carb and YEP there it was, a large vacuum port I had never noticed before and it was just sitting there wide open. Put a plug in, fired it up, what a wonder, ran very well