I just rebuilt a second used Holley 600 as my first one had a worn throttle shaft, now the issue. Both Holleys idled at 1200 or higher as the car would really shake at 1000 or less and vacuum would really suffer. A Holley book that I have says "Engines with long-duration camshafts often will not idle at speeds under 1200 rpm." My Crane cam is a mild hydraulic roller with an intake duration of 222 and exhaust of 234. Is this considered a long duration? I have no clue, thanks.