I have recently started rebuild project on my grandfathers 1978 Ford F-150. The truck was bought off the lot by him back in 1980 , since then it has been through a few motors. The one in it now is a 351m motor which , from what I've read, many of them had. When I started I bought a brand new motocraft carburetor and install it. After getting it hooked up it fires right of everytime I turn the key and runs good for about 30seconds before it dies. If I give it a slight bit of gas I can keep it gong , but when I use the accelerator it the engine pauses to accelerate then catches up its itself. Any info on this would be greatly appreciated. As I am only an amateur mechanic and do not have much experience with carbureturs.
Thank you!

 

First, Welcome to the site.
Second, It sounds like you have not been able to get the truck to run long enough to set the idle I would check the idle set screw (on the throttle where the cable attaches) use 1/8 to 1/4 turns to increase your idle (screw it in to raise idle and unscrew it to lower, just like screwing a screw into the wall) Also the idle jets might be closed to much
This thread has instructions on rebuilding and adjusting a carburetor that might help
https://www.f150forum.com/f13/new-ol...d-help-324696/

Hope this helps

 

So you bought a brand new motorcraft carb and installed it...great pick. Did you actually tune it at all? Because it sounds to me like you didn't based on your complaint. While it probably ships with the most basic of settings, you can't just slap it on and expect it to run perfectly. If you haven't tuned it let us know and I'll send you the guide i send everyone. You'll be running beautifully in no time.

EDIT: The guide I was speaking of is linked above. Follow those instructions to set and tune the carb. Then we can help you work on your finer bugs.

 

[QUOTE=kBaymiller;4536360]I have recently started rebuild project on my grandfathers 1978 Ford F-150. The truck was bought off the lot by him back in 1980 , since then it has been through a few motors. The one in it now is a 351m motor which , from what I've read, many of them had. When I started I bought a brand new motocraft carburetor and install it. After getting it hooked up it fires right of everytime I turn the key and runs good for about 30seconds before it dies. If I give it a slight bit of gas I can keep it gong , but when I use the accelerator it the engine pauses to accelerate then catches up its itself. Any info on this would be greatly appreciated. As I am only an amateur mechanic and do not have much experience with carbureturs.
Thank you![/QUOTE
Let me start by saying that... in your signature, You should describe the specifications of your truck. It helps. Secondly, it always helps to include pictures of the components that you are inquiring about. Third, it's good to know what area/climate you are in, as climate/elevation makes a huge difference when it comes to carburation. Why I say this, is....it sounds like the choke is not operating properly, not allowing the engine to run long enough to adjust anything else, IF anything else needs adjustment.
Is it a M2100 2v or a M4100 4v ? Take the time to toss some pics our way.