carb trouble
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Senior User
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carb trouble
Hey guys
I have 77 f150 w/400 C6. I have had this problem acople of time. it seems to happen radomly. When i start the truck and back out of the driveway its fine. but the next time i go to take of the enging practically dies and then it wont idle right. it idles at like 200. If i put the truck in neutral and try to rev it wont go over 2000. I can temporarily fix it by jiggling the throttlle linkage and all the other stuff on the carb in side the enging caompartment and then rev it while i am in there. When you do this the RPM come back up and its fine. This is a really irrtitating thing. Any suggestions?
Thanks
David
I have 77 f150 w/400 C6. I have had this problem acople of time. it seems to happen radomly. When i start the truck and back out of the driveway its fine. but the next time i go to take of the enging practically dies and then it wont idle right. it idles at like 200. If i put the truck in neutral and try to rev it wont go over 2000. I can temporarily fix it by jiggling the throttlle linkage and all the other stuff on the carb in side the enging caompartment and then rev it while i am in there. When you do this the RPM come back up and its fine. This is a really irrtitating thing. Any suggestions?
Thanks
David
Freshman User
Joined: Feb 2004
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From: Wolfforth, TX
What type of carb do you have and also does the shaft on the base plate have a lot of play? My 59 F-100 has a 400M had the factory 2bbl motorcraft but the bushings the butterfly shaft on the baseplate were worn which caused a vaccumm leak so every few times I would hit the throttle the truck would sputter and loose power.
Laughing Gas
Joined: Jun 2003
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From: Chino, California
AKA: Carter AFB,--an excellent carb.
I have got to ask you--- what was the original carb? Was it a 2bbl or 4bbl. I'll wager an F-150 with a 400 came stock with a 2bbl.
If it was a two barrel, did you change the heads as well? Ford matches heads with carbs on their earlier V-8's.
Does this happen only on cold starts? In other words, is the choke pulling off too soon?
Finally, check for binding in the throttle linkage between the gas pedal and the butterfly shaft. You may not be getting WOT. Playing with the linkage like you are might be unlocking it or freeing it up.
I have got to ask you--- what was the original carb? Was it a 2bbl or 4bbl. I'll wager an F-150 with a 400 came stock with a 2bbl.
If it was a two barrel, did you change the heads as well? Ford matches heads with carbs on their earlier V-8's.
Does this happen only on cold starts? In other words, is the choke pulling off too soon?
Finally, check for binding in the throttle linkage between the gas pedal and the butterfly shaft. You may not be getting WOT. Playing with the linkage like you are might be unlocking it or freeing it up.
Last edited by pops_91710; Feb 24, 2004 at 05:52 PM.
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From: PacNW
I'm not sure "Ford matches heads with carbs" is exactly an accurate statement. True the Cleveland "4V" engines all came with 4V carbs but there was a significant difference between the 2V and 4V heads but you don't hear much about any other Ford engines which had different heads for different carbs. 390s came with 2V and 4V carbs, so did 289s, 302s, 429s and 460s and the heads were the same. Some had higher compression ratios but it was usually accomplished by changing the pistons rather than the combustion chamber design.
All 351M/400 motors came with 2V carbs and the "M" heads were virtually identical to the Cleveland 2V heads so if there's a 4V carb on a 351M there's either an aftermarket intake or an aftermarket adapter installed. Several companies make intake manifolds for putting 4V carbs on vehicles with M or 2V heads.
All 351M/400 motors came with 2V carbs and the "M" heads were virtually identical to the Cleveland 2V heads so if there's a 4V carb on a 351M there's either an aftermarket intake or an aftermarket adapter installed. Several companies make intake manifolds for putting 4V carbs on vehicles with M or 2V heads.
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It happens first thing in the morning and after its been sitting for a while. If I run in the store to grab something and come back out its still fine. So i guess that would be cold starts. i reset the choke in case that was the problem and it still did it. Yesterday when i tied to come home from school it would not get "fixed" even when i messed with the linkage. I finally tried adjusting the idle screws a tad richer (which were in the same place the were months ago). The idle smoothed out i drove home with no poblems. at the time and now i am running the open element and now the carb is not freezing. so i dont know what to do. can i just leave it set the way it is?
Later David
Later David
Last edited by dbarracuda; Feb 24, 2004 at 09:41 PM.
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Posting Guru
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From: PacNW
Originally posted by pops_91710
huh?
I think you just backed me up, Bill.
huh?
I think you just backed me up, Bill.
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dbarracuda-
It sounds like you have a simple choke adjustment problem, try checking with the carb forum here: https://www.ford-trucks.com/forums/f...?s=&forumid=72
It sounds like you have a simple choke adjustment problem, try checking with the carb forum here: https://www.ford-trucks.com/forums/f...?s=&forumid=72
Lead Driver
Joined: Nov 2000
Posts: 6,637
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From: Albuquerque
You could be having intermittant fuel level problems. i.e. dirt in the bowls/inlets.
Oh and 2v heads work just fine with a 4v carb and Performer manifold. Even better on the street than the 4v heads which are problematic at best to adapt to existing manifolds and exhaust.
Oh and 2v heads work just fine with a 4v carb and Performer manifold. Even better on the street than the 4v heads which are problematic at best to adapt to existing manifolds and exhaust.
Last edited by beartracks; Feb 25, 2004 at 11:51 AM.
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"I have got to ask you--- what was the original carb? Was it a 2bbl or 4bbl. I'll wager an F-150 with a 400 came stock with a 2bbl."
He said his truck is a 1959 F-100. Obviously the 400 did not come stock with that engine.
"If it was a two barrel, did you change the heads as well? Ford matches heads with carbs on their earlier V-8's. "
True to some extent, but definitely not with the 335 series. All 351M/400 engine came with 2V carbs only. The heads are identical for all practical purposes to the 351C 2V heads, which are fine for nearly any use for applications past 600 HP.
The 351C 4V heads have such large valves and ports that they really don't work as well as the 2V heads until you get in the 6000 RPM range.
He said his truck is a 1959 F-100. Obviously the 400 did not come stock with that engine.
"If it was a two barrel, did you change the heads as well? Ford matches heads with carbs on their earlier V-8's. "
True to some extent, but definitely not with the 335 series. All 351M/400 engine came with 2V carbs only. The heads are identical for all practical purposes to the 351C 2V heads, which are fine for nearly any use for applications past 600 HP.
The 351C 4V heads have such large valves and ports that they really don't work as well as the 2V heads until you get in the 6000 RPM range.
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From: Wolfforth, TX
My 59 has a 1978 400 with a decent FMX tranny. All the 351M -400 engines I have seen have a 2bbl. I still have the stock cast iron intake but added a Holley 500cfm 2bbl since I didnt feel like spending money on a new intake.