New Motorcraft Carb
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Senior User
Joined: Jul 2002
Posts: 145
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New Motorcraft Carb
I just installed a new motorcraft 2v carb on my 1978 f150 with a 351M. All the vacuum lines are the same and it has an auto tranny. I tried setting the choke and idle and it either runs too fast or rough as hell at a low idle....I replaced the replacment carb that was on there that started leaking and it never ran like this. I dont know what to do. I let it run and warm up and even went down the road and back. Why so rough and fast, why cant there be a slower smoother idle?
Post Fiend
Joined: Apr 2002
Posts: 7,157
Likes: 1
From: Central Kali
New Motorcraft Carb
Did you try adjusting the idle mixture screws? Try them at 1 1/2 turns out. Then adjust for highest vacuum reading. Does the choke open ok and does the fast idle cam drop out when you give it a little gas? After this I would check the float level. 
Cargo Master
Joined: Aug 2002
Posts: 2,013
Likes: 6
From: Cajun Country
New Motorcraft Carb
Use a vacuum gauge to adjust the idle mixture screws to the highest setting then turn them in 1/4 turn.If that doesnt do it,could be the float sticking or maybe very small dirt particles.
