carb problems
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Senior User
Joined: Oct 2009
Posts: 396
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From: toledo oh
carb problems
have a 77 351m400(its the 400), with a 2bl carb. stock. i'm starting to get annoyed with this problem i have, that's been happening for ever. when i initially start it up, it'll run with "fast idle". which i feel is normal, since it's about 20d in the morning here. but, sometimes if i gas it really quick, it'll knock down to "slow idle or normal". about 8 or 900rpm. but, 95% of the time, i can't get it to kick down. i don't have a "manual" choke hooked up, but i think i need to bc i have a feeling somethings wrong with the type thats on it, but i'm not sure
. any help would be awesome. maybe pictures for explanation? or how it's supposed to work. THANKS
. any help would be awesome. maybe pictures for explanation? or how it's supposed to work. THANKS
Post Fiend
Joined: Mar 2011
Posts: 8,501
Likes: 4
From: Lynchburg, VA
fmc400 wrote an excellent writeup of how to adjust your choke
https://www.ford-trucks.com/forums/7...ot-idle-2.html
https://www.ford-trucks.com/forums/7...ot-idle-2.html
Thread Starter
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Senior User
Joined: Oct 2009
Posts: 396
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From: toledo oh
i have somewhat adjusted the carb with the screws, and have adjusted timing by moving distributor. when i replaced the motor (400) that came in the truck with another 400, i put the same carb on it. the carb at the time had zip ties holding that "valve at open. so after i cut those off i did "adjustments". this is when this problem started. i tried zip tieing it open again but with my adjustments i probably threw that all off. bc it would idle fine but under load it would stall. im going to read that link you posted now, and see what i can come up with. THANKS
Thread Starter
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Senior User
Joined: Oct 2009
Posts: 396
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From: toledo oh
A lot of info on there. which is very helpful, if i could understand jibberish. LOL. i'm thinking maybe ill just throw the 4bl carb i have in the garage, along with the intake, on the motor and go from there. but, in the morning, i might feel up to learning a lot about carbs lol. Thanks for the replies!
Rusty Roller
Joined: Oct 2011
Posts: 1,423
Likes: 5
From: Santa Cruz Mountains
All carbs need adjustment. Just because one runs fine on another engine doesn't mean it will be correct for yours.
I hope you aren't referring to fmc400's instructions on how to adjust a choke.... In the 10 mins between your posts I doubt you read the way to do it correctly or understand what great info you were presented. Sorry but swapping out the manifold and carb ISN'T going to allow you to get around ADJUSTING BY PROCEDURE any carb.
Adjustment has to be done in the correct order one step at a time. Shortcuts result in problems. Zip ties don't belong on a carb and what is the "valve" you are referring to? The choke?
The factory service manual for this carb is 15 pages. Turning a couple of screws won't get you where you need to be....
Again Sorry but your answer just struck the wrong cord for me.... lol's or not.
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if i could understand jibberish
Adjustment has to be done in the correct order one step at a time. Shortcuts result in problems. Zip ties don't belong on a carb and what is the "valve" you are referring to? The choke?
The factory service manual for this carb is 15 pages. Turning a couple of screws won't get you where you need to be....
Again Sorry but your answer just struck the wrong cord for me.... lol's or not.
.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I don't know how else to help someone other than write out logical steps in clear English.
Good luck solving your problems by swapping out parts.
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