Motorcraft 4350 carb secret adjustments...

[wayne petty]

just got finished with the van carb..  snapped some photos...  the motorcraft 4350 has adjustability just like the quadrajet carbs.... most people throw them away...  put on a Holley square bore after changing the manifold or getting the adaptor....


i always read the instructions after i finish .. just to see how i do... and this carb had been apart before..  zinc carb colored paint tells me so... it has not worked well...  choke pull off not working... accelerator pump not working well...  tromp on it hard and it will lean back fire out the top of the carb...

on these carbs... try to read the instructions up front... there are a few measurements you want to know about first...

the metering rod assembly is adjustable under this aluminum plug... so it is important when you get it out... to measure it ...

[wayne petty]

the carb had some problems.. i described earlier...


like an almost non functioning accelerator pump system...

seems when they put the reman together... the check ball under the cover gasket was off to one side...   so it was not stopping the pump from pulling the charge back.. and for added insult...  it was blocking one shooter nozzle...    this has to be why it would be almost impossible to start cold.. and POP hard on acceleration....


the metering rod adjustment was all the way to the rich side...  the build paper did not show how much the adjustment should be.. i plan on some driving and some tuning...

 on the choke side of things... they used some type of thick grease for the choke shaft... so it would hang up.. they also snapped off the choke pull off piston...    i had gotten a worn out spare carb  from my friend at the junk yard...   so i was able to grab some parts off of it..

i am starting with the adjustment out two turns from full lean...


seems the accelerator pump lever also has some authority over the metering rod holder...  there is a small rod that keeps it from going too rich without the proper amount of throttle...     this is also something that i did not get to measure... as everything had been messed with...

there are also idle air bypass circuits on this carb...   they are sealed...  and it is probably a good idea not to mess with them...  the are angled in from the sides in the throttle plate ..


hopefully these tidbits will help somebody farther down the line...

[wayne petty]

also.... if you buy a kit.....  check to see if the plastic has been opened..  if it has... reject it...  somebody has robbed a part out of it...  and returned it...  i special ordered the kit for this one... when i got it...  it had been opened.. and returned ... to the shelf...  i took a chance.. but ended up using one of the gaskets from the carb...  as the exact gasket i needed was missing... along with the aluminum plugs and check balls....

wayne...

[Mikej]

Is that a 70's era carb? The vent is controlled by the throttle linkage? Saving gas..Emissions control

[wayne petty]

yes.... it is for a 76 ford Econoline with the 460 option...

the insert said to set it so the valve is closed when the idle stop solenoid is on... holding the throttle at normal idle... and when the key is turned off.. the  idle solenoid releases, the throttle drops to the stop screw and the vent should open then...

i got it on today...   wow what a difference... starts fast... smooth acceleration...  and i hope a lot better than the 9 mpg i was getting...  i set it at 2 turns down on the metering rod.. 3 turns out on the idle mixture screws...  i have to find the collared screwdriver tip i put together for adjusting the idle mixture screws...   it is hard to keep a screw driver on the screws.. i did have some 5/16 valve guide liners i was going to cut down to slip over the screw heads.

[junkyardjeff]

If I can find a decent carb could you go through one for me,the 460 in my 77 F150 originally had one but I got a square flange on it now but it does not run like it should.  When I bought it the PO adapted a Q jet and it ran like crap so I put on a square flange holley I had in stock and it runs alot better but its still not right.  Jeff

[wayne petty]

If I can find a decent carb could you go through one for me,the 460 in my 77 F150 originally had one but I got a square flange on it now but it does not run like it should.  When I bought it the PO adapted a Q jet and it ran like crap so I put on a square flange holley I had in stock and it runs alot better but its still not right.  Jeff

i have a 95 percent complete carb... i have to bush the throttle shaft bore... and find a replacement choke pull off piston and lever assy..  maybe one out of a 2100 will fit... i will throw that together in a week or two.. and let you know..