I can't seem to get the idle speed on my 86 F150 351W up to spec unless I open the throtle plates enough to start getting into the transfer slots in the primaries. This is a Holley 4180 carb. I recently pulled the carb to replace the base gasket. While I had it off, I checked the secondary idle screw and found that the secondary throttle plates were open past the transfer slots. I reset the secondary throttle as far open as I could without getting into the transfer slots. I then checked the primary and found the same situation. I set the primary throttle just like the secondaries. After re-installing, the truck fired right up but would only idle at 600 rpm in neutral. Normal idle in neutral is around 800. Once you put it in D, idle drops to less than 500. It will idle that low, but not well Since I purchased this carb rebuilt, the mixture screws are already exposed so I tried adjusting mixture. There was minimal efffect on idle speed until I got the mixture screws near closed. I checked for vacuum leaks, but could not find any.
Any ideas?
AmmonMan