holley q?

A 750 double pumper is a pretty big carb for most small blocks. It may be too big for a 383 unless you've got compression and a big cam. Holleys are noted for the metering block gaskets shrinking and drying up after the carb sets for a while. Is it a fresh carb or a swap meet find? It may need a overhaul. Have you adjusted the idle mixture? They are the little screws on the side of the metering block (the 1" thick blocks between the float bowls and the main body). A tune-up tech would have a tach and a vacuum gauge but you can help it by ear. Slowly screw one screw in no more than a half turn at a time. Listen to the
engine . If it starts to smooth out turn it in another 1/2 turn. adjust side to side until it runs its best. The adjustments may make it idle too high which you can adjust by loostening the idle speed screw( near the throttle cable). If the engine runs worse or doesn't respond to adjustments it needs rebuilt. If you have a stock 273 or 318 a 600 or 650 is plenty. Bigger engine and more modifications/ bigger carb. An engine usually runs better with a smaller carb jetted up yhan a large carb jetted down. Hope this helps! Toolmanmike