View Full Version : 70 AMX Motorcraft 4300 Carb modifications?

04-17-2005, 12:01 AM
Has anyone tried modifying the 70 Motorcraft 4300 carb for performance? I have a fresh 70 AMX motor, with pocketported heads, free flowing exhaust, and a slightly bigger cam than stock. I have a dyno session coming up, and would love to run a Holley, but am going to try a rebuilt 4300 carb. I cannot find anyone who knows anything about modifying it. How can it be richened up to work with mods to the 390 motor? Drill out the primary jets? How much? Can the secondaries be richened? I have read that these carbs ran lean in stock form for emissions. Can anyone help?

04-19-2005, 09:04 AM
Sorry, but I am not much help here. Those carbs I kind of trashed in favor of the Edelbrook Performer Carb (Carter AFB). The Carter's are easier to modify and the parts are easier to come by. I know that Motorcrafts 4300 series carbs have rebuild kits that are still avialable thru the local parts stores, but that is about the extent of what I know. I would suggest that you modify to a Edelbrook or Holley. Both of which are decent carbs for the price.

05-04-2005, 01:48 PM
Check out these people. They do Ford carbs and have articals about the 4300 carb. http://www.ponycarburetors.com/