351M/400M rough under load
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Joined: May 2013
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351M/400M rough under load
Hello,
I have a Bronco with a 351 or 400, It starts and runs good except at speeds around 40-50, then it falls on its face. It sputters and bogs down until I let out of the throttle. I dont think the timing would make it run this bad, to me it seems like its running otu of fuel, It has the original 2bl carb. Would it be a bad idea to get like a 600 cfm carb?
Thanks,
-Lance
I have a Bronco with a 351 or 400, It starts and runs good except at speeds around 40-50, then it falls on its face. It sputters and bogs down until I let out of the throttle. I dont think the timing would make it run this bad, to me it seems like its running otu of fuel, It has the original 2bl carb. Would it be a bad idea to get like a 600 cfm carb?
Thanks,
-Lance
Junior User
Joined: Feb 2011
Posts: 60
Likes: 0
From: Round Rock, Tx
Hello,
I have a Bronco with a 351 or 400, It starts and runs good except at speeds around 40-50, then it falls on its face. It sputters and bogs down until I let out of the throttle. I dont think the timing would make it run this bad, to me it seems like its running otu of fuel, It has the original 2bl carb. Would it be a bad idea to get like a 600 cfm carb?
Thanks,
-Lance
I have a Bronco with a 351 or 400, It starts and runs good except at speeds around 40-50, then it falls on its face. It sputters and bogs down until I let out of the throttle. I dont think the timing would make it run this bad, to me it seems like its running otu of fuel, It has the original 2bl carb. Would it be a bad idea to get like a 600 cfm carb?
Thanks,
-Lance
Elder User
Joined: Dec 2010
Posts: 600
Likes: 1
From: New Carlisle, Ohio
When it does that shut it off and coast to a stop then pull your air cleaner off open the throttle and see if it's getting a pump shot. If it's not you may have a bad fuel pump. Does this happen all the time or just when the truck is warmed up?
Fleet Mechanic
Joined: Feb 2007
Posts: 1,326
Likes: 48
From: Middle TN
Change your fuel filters especially the one screwed into the carb. Check your rubber fuel lines if you use 10% ethanol fuel. They will deteriate on the inside and pieces of hard rubber will flake off and stop up your filters.
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