I HAVE A 351M ENGINE IN MY TRUCK . IT RUN'S BUT I'M HAVING SOME PROBLEM'S WITH THE IDLE VACUUM. Adjusted carburetor, but i don't know how many turns are needed to set the carburetor on the adjustment screws. The vacuum seems to be working but it still runs kind of high as if i had a leak, but none are present. The truck has no emmissions. I've tried adjusting the distributer, but when i turn down the distributer, it tends to run rough, or not at all. When i turn the distributer up, it starts but runs high. I'm thinking that the vacuum plate under the carburetor may be wrong plate, but i'm not sure. Any suggestions on where to get a new 2bbl plate for '78 ford f-250 with a 351M engine. Please reply with any references or any clues. Any technical help for this motor would be greatly appreciated. Have many little problems that need to be weeded out.

did you lower the ldle

I HAVE A 351M ENGINE IN MY TRUCK . IT RUN'S BUT I'M HAVING SOME PROBLEM'S WITH THE IDLE VACUUM. Adjusted carburetor, but i don't know how many turns are needed to set the carburetor on the adjustment screws. The vacuum seems to be working but it still runs kind of high as if i had a leak, but none are present. The truck has no emmissions. I've tried adjusting the distributer, but when i turn down the distributer, it tends to run rough, or not at all. When i turn the distributer up, it starts but runs high. I'm thinking that the vacuum plate under the carburetor may be wrong plate, but i'm not sure. Any suggestions on where to get a new 2bbl plate for '78 ford f-250 with a 351M engine. Please reply with any references or any clues. Any technical help for this motor would be greatly appreciated. Have many little problems that need to be weeded out.


Vacuum at idle should be 17-22 in.Hg and the needle should be steady
With a vacuum leak you will get a low reading
Adjust the idle mixture screws with a tach. When the tach is at it's highest rpm before falling of that's where you want it. go slow and let the carb adjust to the speed change.
Set ignition timing (Moving the distributer) with a timing light

Perform a leakdown test and/or a compression test to evaluate the cylinders and valves conditions