I have a 600 cfm 4160 Holley Carburetor on my 75 Sprint the engine is a 350. It always has had a slight hesitation when accelerating. Took it to a shop and they worked on the timing and fixed some issues with the carb. When I paid the bill he said it needs a 10.5 power valve in it and that would take care of the hesitation. Was wondering if this sounds correct or not.