Calling all carburetor men
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New User
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Calling all carburetor men
Hey folks, new to the forum and glad to be here. So, i got a 79 f150 with the 400 in it. just bought the truck, previous owner had a carb for a 454 on it. so needless to say shes runnin a bit rich. Guessin i need to change the jets so. Question is what jet size number??? much apprechiatted
Fleet Owner
Joined: Dec 2009
Posts: 20,678
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From: NorCal
Hey folks, new to the forum and glad to be here. So, i got a 79 f150 with the 400 in it. just bought the truck, previous owner had a carb for a 454 on it. so needless to say shes runnin a bit rich. Guessin i need to change the jets so. Question is what jet size number??? much apprechiatted
A Quadrajet
? I say change'em to 72 in the primaries and 88s in the secondaries. 
"Guessin' you need to change the jets??? C'mom man... Seriously?.. your question, is well, ummmmm..... uninformed. Why don't you try tuning the carb first (plus do a tune up!)? Then if that doesn't work then maybe consider changing the jetting.... YOU have to determine what jets are installed... it's not like we can make a recommendation without you doing some homework on your end and then providing more info.
R/
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New User
Joined: Mar 2013
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Welcome to the forum.
A Quadrajet? I say change'em to 72 in the primaries and 88s in the secondaries.
"Guessin' you need to change the jets??? C'mom man... Seriously?.. your question, is well, ummmmm..... uninformed. Why don't you try tuning the carb first (plus do a tune up!)? Then if that doesn't work then maybe consider changing the jetting.... YOU have to determine what jets are installed... it's not like we can make a recommendation without you doing some homework on your end and then providing more info.
R/
A Quadrajet
? I say change'em to 72 in the primaries and 88s in the secondaries. "Guessin' you need to change the jets??? C'mom man... Seriously?.. your question, is well, ummmmm..... uninformed. Why don't you try tuning the carb first (plus do a tune up!)? Then if that doesn't work then maybe consider changing the jetting.... YOU have to determine what jets are installed... it's not like we can make a recommendation without you doing some homework on your end and then providing more info.
R/
Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
I can see why you would ask that but from what your sayin a better question would be did the old boy have what it takes to set up a quadrajet carb from a 454 correctly on a 400 ford motor? why do you say it's running rich? Is the choke working properly?
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
What is the base timing? Overall timing?
Is it a pre-75 Quadrejet or a 75 and newer?
What is its CFM rating? 750? or a rare 800?
Any mods to the engine?
How much vacuum is it generating?
What jets are currently installed in the primaries and secondaries?
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choke seems fine. runnin down the road u can smell it like its flooded. truck actually quit on me after sputtering a bit bringing it home. friend behind me noticed black smoke.. im just goin off of what the old owner told me and comin to u guys on advice and what to do or try first
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Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
choke seems fine. runnin down the road u can smell it like its flooded. truck actually quit on me after sputtering a bit bringing it home. friend behind me noticed black smoke.. im just goin off of what the old owner told me and comin to u guys on advice and what to do or try first
stuck float? fuel leak causes low fuel pressure ? also pull the dip stick and see if you smell a gas smell in the oil?
Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
If you can answer the questions HIO Silver asked in post #7 then you'll be well on your way to telling what we're working with and begin to determine if it is set up right for your 400
Cargo Master
Joined: May 2009
Posts: 2,587
Likes: 47
From: Eagle River, AK
Welcome to the forum.
A Quadrajet? I say change'em to 72 in the primaries and 88s in the secondaries.
"Guessin' you need to change the jets??? C'mom man... Seriously?.. your question, is well, ummmmm..... uninformed. Why don't you try tuning the carb first (plus do a tune up!)? Then if that doesn't work then maybe consider changing the jetting.... YOU have to determine what jets are installed... it's not like we can make a recommendation without you doing some homework on your end and then providing more info.
R/
A Quadrajet
? I say change'em to 72 in the primaries and 88s in the secondaries. "Guessin' you need to change the jets??? C'mom man... Seriously?.. your question, is well, ummmmm..... uninformed. Why don't you try tuning the carb first (plus do a tune up!)? Then if that doesn't work then maybe consider changing the jetting.... YOU have to determine what jets are installed... it's not like we can make a recommendation without you doing some homework on your end and then providing more info.
R/
Okay..... fabulous. You've already done a tune up and already narrowed it down to the jets....Awesome.
What is the base timing? Overall timing?
Is it a pre-75 Quadrejet or a 75 and newer?
What is its CFM rating? 750? or a rare 800?
Any mods to the engine?
How much vacuum is it generating?
What jets are currently installed in the primaries and secondaries?
What is the base timing? Overall timing?
Is it a pre-75 Quadrejet or a 75 and newer?
What is its CFM rating? 750? or a rare 800?
Any mods to the engine?
How much vacuum is it generating?
What jets are currently installed in the primaries and secondaries?
If you can answer the questions HIO Silver asked in post #7 then you'll be well on your way to telling what we're working with and begin to determine if it is set up right for your 400
"This forum is a great asset and will definately help you along the way.
First off - Please use proper (or at least readable spelling) and punctuation, it will really help the people that may be able to help you read and understand your problem.
Secondly - While some members seem a little harsh and short with what they are requesting you to do..... Just think and do a little searching on this site and others, these folks are short because they are trying to make it very clear what information they NEED to help YOU find your problem and fix it. These folks also help lots of members worldwide and this is what we all do as a "side-job".
Anyhow, rant over.... I certainly hope you get your rig fixed.
"Happy motoring my friend, these folks will get you going in no time.
Welcome to FTE
Cargo Master
Joined: Apr 2009
Posts: 3,038
Likes: 4
From: South west Idaho
Hey folks, new to the forum and glad to be here. So, i got a 79 f150 with the 400 in it. just bought the truck, previous owner had a carb for a 454 on it. so needless to say shes runnin a bit rich. Guessin i need to change the jets so. Question is what jet size number??? much apprechiatted
Cargo Master
Joined: Nov 2009
Posts: 2,364
Likes: 117
From: starship enterprise
All good advice. Are you at sea level? If not, then what elevation? What is the fuel pressure? Is the fuel filter good? I am going to say that the fuel filter is a different aftermarket since these engines had one that threaded into the carburetor. How is your vaccum advance hooked up? ported vaccum or not? What gas is in it and how old?
Verify the firing order, good gas, good plugs, filters, wires, cap, rotor, timing, fuel pressure, I have pulled my hair out working on carburetors and ignition components on old farm trucks that only run a few times a year and come to find out new gas fixed them, no need for new parts at all.
Verify the firing order, good gas, good plugs, filters, wires, cap, rotor, timing, fuel pressure, I have pulled my hair out working on carburetors and ignition components on old farm trucks that only run a few times a year and come to find out new gas fixed them, no need for new parts at all.