I have just purchased a 78 F150 (2WD) with a 75 or so 460-4V and C6 trans. with a 4350 motorcraft carb. The engine runs and idles good. When I ease the throttle open it sounds as if it is skipping and has a laboring sound until the engine gets to about 1000 to 1500 rpm then it frees up and runs great.

Had to replace the vacuum advance it was not working. Set timing at 14deg. BTDC and adjusted carb as best as I could. the right side idle mixture screw (viewing from front of engine) has no effect weather closed in all the way or open two to three turns. Removed screw and shot carb and choke cleaner in hole and followed with compressed air. Replaced screw and no difference.

When I put trans. in gear and start to pull off it seems as it is skipping, and does not take gas very well when you try to hit the throttle hard. Does not even act like the secondaries try to come in. I have checked for vacuum leaks and it appears not to have any.

Has anyone else had or have some of these problems?? Would appreciate any help or advice that anyone has that I may have over looked or just plain don't know.

Thanks Leland

 

For one you need to rebuild that carb to get that fuel screw working. I'm thinking that a good rebuild including a long carb dip will cure your issue.

 

I will agree with that, not knowing how long this truck sat before buying it. Is there any mods. or tricks I need to do while I have it tore down??

I hope you are correct on the rebuild (cure my problems). I have read that these were the best built and best operating carbs ever built. Do you agree?

Thanks for your reply!!

 

Agree with rebuilding carb. Look down throat of carb(not running) and move the accelerator. You should see it shooting gas instantly, if not, accelerator pump is not working or clogged. It is what makes the transition from idle circuit to regular running.

 

Thanks, I will look as I should have done already!! Over looking the most important step!!

Thanks Leland

 

After doing some searching I have definitely found a few problems. Accelerator pump not working, gas tank got rust in it, and secondaries not opening. So a rebuild is definitely going to happen, and removing the gas tank to clean or replace.

On this carb the secondary butterflies (the ones in the throttle plate) open by linkage and the top baffles open from engine vacuum, is this right ?? Which I know that when I soak the carb I will be able to get them working, just want to try to get them to open before I remove the carb.

Thanks for your help;
Leland