motorcraft 4300 carb info

Jeff Lee · 09-30-2008, 11:27 PM

The AMC 360-390-401 of 1970 thru 1972 (390 was discontinued with the introduction of the 401) used the square flange (Holley, Carter, etc., interchange) with the 1 9/16" x 1 11/16" throttle blade size as correctly mentioned by Garrett. After 1972 AMC used the spread-bore flange on the 360-401 which was also used on the FOMOCO 429-460 engines.
I've found the 4300 to be a decent carb with the exception of the bowl size and of course CFM. Although not as bad as a Q-Jet fuel bowl I suppose. I've found it is well engineered as BSFC numbers are pretty decent with just jetting changes (there are no secondary jetting or metering rods). In fact, when we started playing with air bleed sizes, minute changes +/- from stock just killed power. And the fuel bowl wasn't an issue untill I started running Superstock and that problem was also corrected. But it definetly is not of sufficient CFM for a 390 engine!
Now if only we could get those pesky 351 Boss and Clevlands to also run the factory supplied carb, we would really see who was on top of their game!

09-30-2008, 11:27 PM	#11
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: motorcraft 4300 carb info The AMC 360-390-401 of 1970 thru 1972 (390 was discontinued with the introduction of the 401) used the square flange (Holley, Carter, etc., interchange) with the 1 9/16" x 1 11/16" throttle blade size as correctly mentioned by Garrett. After 1972 AMC used the spread-bore flange on the 360-401 which was also used on the FOMOCO 429-460 engines. I've found the 4300 to be a decent carb with the exception of the bowl size and of course CFM. Although not as bad as a Q-Jet fuel bowl I suppose. I've found it is well engineered as BSFC numbers are pretty decent with just jetting changes (there are no secondary jetting or metering rods). In fact, when we started playing with air bleed sizes, minute changes +/- from stock just killed power. And the fuel bowl wasn't an issue untill I started running Superstock and that problem was also corrected. But it definetly is not of sufficient CFM for a 390 engine! Now if only we could get those pesky 351 Boss and Clevlands to also run the factory supplied carb, we would really see who was on top of their game! __________________ Jeff Lee 7494 D/S '70 AMX