I'm using a holley 4000 carb on my 53 Ford Customline with a 255 Merc flathead. I know it's not y block but the carb is. Anyways I have a massive hesitation. The carb doesn't transition between idle and higher rpms very well. It does get a good shot of gas when pumped, but I just can't get this one to run right and when I first put it on it ran really well. I figured someone must know these carbs really well so I thought I'd ask.