Carburetor help again !!
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Senior User
Joined: May 2005
Posts: 447
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From: Jacksonville IL
Carburetor help again !!
Hi ! This is my first Ford pickup. A 79 Ford F100. So, limited knowledge on stuff.
Got a 302 Engine, but don't know if any performance upgrade was done to it - just know that it was rebuilt. Runs great.
Problem: Gas guzzler - gives less than 10 miles a gallon. Suspect carb is the problem. It has a AFB Carter Competition series carb - says Weber on the side. Any ideas on this carb?
What carb should I choose for this engine, assuming that there may be some kind of performance cam installed?
Any help will be appreciated.
Got a 302 Engine, but don't know if any performance upgrade was done to it - just know that it was rebuilt. Runs great.
Problem: Gas guzzler - gives less than 10 miles a gallon. Suspect carb is the problem. It has a AFB Carter Competition series carb - says Weber on the side. Any ideas on this carb?
What carb should I choose for this engine, assuming that there may be some kind of performance cam installed?
Any help will be appreciated.
Posting Guru
Joined: Jul 2003
Posts: 2,232
Likes: 1
From: Colville, Washington
A Carter AFB is an excellent street carb, it is possible that it is simply jetted and rodded too rich. Look around the baseplate for the carb number-should be something like 9635 or 9605 etc. and post back. You can also remove the top of the carb and check metering rod and main jet sizes.
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Senior User
Joined: May 2005
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From: Jacksonville IL
I checked the base plate and saw the numbers 9502S. I am guessing it is a 500 cfm 4BBL. I cannot say that I ever had trouble starting or running my truck. I took the plugs out and I could see that it is running a little rich (carbon deposit), but I do not see them soaked with gas.
I am about to go out and buy myself a Edelbrock 600 cfm with electric choke (1406).
I am not carb savy so I will really appreciate your help. Also, can you tell me what RPM should the engine run when idling?
I am about to go out and buy myself a Edelbrock 600 cfm with electric choke (1406).
I am not carb savy so I will really appreciate your help. Also, can you tell me what RPM should the engine run when idling?
Elder User
Joined: Jan 2004
Posts: 767
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From: Franklin, GA
Congrats on the "new" truck. Although the mileage is in the cellar range of acceptability, isolating the carburetor as the sole reason may disappoint you when you get that new E-brock bolted on. I would evaluate all aspects of an extensive tune up prior to making a decision to replace the carb. Things such as plugs, plug wires, timing, vacuum advance, manifold vacuum, air filter, PCV valves, dist. cap and rotor button, and carb/choke adjustment work together to give you good or bad mileage. Not to say that your carb isn't causing your mileage to suffer, but with a mpg number like you stated, I doubt the carb is the only thing contributing to the lousy gas mileage. Oh yeah, just thought about rear end gearing. Low gears means higher RPMs. Combine those and it equals low mileage also.
Elder User
Joined: Apr 2005
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From: UTI student
Just so you know edelbrock and carter are identical carbs. The only thing you would be doing is replacing an older, smaller carb for a new and slightly larger one. To be completly honest with you I would spend the 250 odd dollars and rebuild the carter, put fresh parts in the dizzy, replace vacuum hoses (if needed), fuel filter and set the timming. I would also replace plugs and wires if it needs them. Depending on the cost of parts you may be able to get headers for that 302. I don't know how much 302 headers run but I paid 125 for my 390 headers. I have had both edelbrock and carter AFB carbs. Both were the same thing on the inside. I rebuilt both it's not hard just time consuming. Just an idea.
Edit: Those carbs need rebuilding a little more often in my opion
Edit: Those carbs need rebuilding a little more often in my opion
Last edited by hatemakings/n; May 25, 2005 at 10:50 PM.
Thread Starter
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Senior User
Joined: May 2005
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From: Jacksonville IL
I bought this truck from someone who is a mechanic in local Ford Dealer. According to him, the engine is re-built not too long ago. Although, he left the Dealer and started his own business in a nearby town, but I cannot seem to locate him anymore. Anyway, after I got the truck, I did change the rotor cap, spark plugs, spark plug wires. I changed the fuel filter as well. It seems to idle ok - won't it idle rough if there is a vaccum leak? That's one reason I wanted to find out what RPM the engine should idle. I put a tach and adjusted a screw (I guess it is the idle screw) on the driver's side of the carburetor till I got RPM about 720 - 730. Then I set the base timing with a timing light.
I do not know what the rear end gearing is. All I can say is that when driving in town about 35 MPH, my tach in dash board says somewhere around the 1200 -1500 figure.
My vacuum advance from the distributor does not work. It is just dangling free. Don't really know where it hooks up.
Looking forward to your valuable replies.
I do not know what the rear end gearing is. All I can say is that when driving in town about 35 MPH, my tach in dash board says somewhere around the 1200 -1500 figure.
My vacuum advance from the distributor does not work. It is just dangling free. Don't really know where it hooks up.
Looking forward to your valuable replies.
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Elder User
Joined: Apr 2005
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From: UTI student
The vacuum advance hose connects to the carb. On the front of the carb at the base there are three vacuum ports. One big one in the middle and two small to either side. IIRC the vacum advance should connect to the small port. The big port should have a hose to the PCV system. I never used the second small port. Somebody else will chim in if I'm wrong. Try hooking the vacum advance to the port and see what happens you might find problem isn't AS bad. I still recommend rebuilding that carb if it looks like it's been sitting.
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Thread Starter
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Senior User
Joined: May 2005
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From: Jacksonville IL
Maybe a dumb question: what is this 'dizzy'?
Also, can you provide me with instructions how to tune the carburetor? I can try that out first. I have no idea what screws do what. So, I do not want to touch them until I know what they meant.
Also, can you provide me with instructions how to tune the carburetor? I can try that out first. I have no idea what screws do what. So, I do not want to touch them until I know what they meant.
Posting Guru
Joined: Nov 2004
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From: Asheville, NC
Some of the guys here seem to think that 'dizzy' is acceptable for 'distributor.' Not me. it looks goofy.
You dont want to start turning screws at random on the carburetor. Thats the best way to thoroughly screw it up.
The fast idle adjustments are usually on the same side of the carb as the choke coil. Dont adjust these unless the motor is cold. The main idle adjustment should be on the throttle attachment side. You may have found it already.
You dont want to start turning screws at random on the carburetor. Thats the best way to thoroughly screw it up.
The fast idle adjustments are usually on the same side of the carb as the choke coil. Dont adjust these unless the motor is cold. The main idle adjustment should be on the throttle attachment side. You may have found it already.
Last edited by Holmesuser01; May 26, 2005 at 11:14 PM.
Elder User
Joined: Apr 2005
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From: UTI student
In addition to what Holmesuser01 said there are also two screws in the front on the throttle plate. One on each side of the vacuum ports. These should only be adjusted if it runs rich or lean at idle iirc. I went to look for my old instruction sheet but couldn't find it. I know guys like Putt can help you alot more. I don't want to give you bad intel and screw your stuff up even more. For my edelbrock carb I ended up about 2 turns out after I seated the idle mixture screws. But that was for my carb. Yours could be different. On the carb vacuum ports if they AREN'T being used make sure they are capped off. I know it seems like a no brainer but I got a car that ran really rough. Had to keep your foot on the gas to keep it running. Got it home and was looking at it the next day in the day light when I noticed the vacum cap was missing. Put one on and it ran perfect after that.
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Senior User
Joined: May 2005
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From: Jacksonville IL
Oopsi !! Too late on the advise Hatemakings!
Yesterday, I took it to a local garage. He messed with those two screws and my truck started idling high ! I wanted him to take a look at my carb. He looked at it screwed with the screws and told me he is not sure what he can do to improve my gas mileage.
So, how do I set them right now?
Yesterday, I took it to a local garage. He messed with those two screws and my truck started idling high ! I wanted him to take a look at my carb. He looked at it screwed with the screws and told me he is not sure what he can do to improve my gas mileage.
So, how do I set them right now?
Fleet Owner
Joined: Jan 2004
Posts: 26,007
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From: Brentwood,CA
so it sounds like he made it lean you need a vacuum gauge to set it right and you would do yourself a favor and replace the carb with a holley 1850s 600 cfm carb has very few adjustments and gives decent mileage your rpms around town are kind of high you might have something like a 4.10 rearend when i cruise around town about 35 40 i see about 1,100 and 1,900 freeway but thats with a 3.00 rear end
Elder User
Joined: Apr 2005
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From: UTI student
I recomend Holley also but a new carb isn't always possible or feasable. The Carter/Edelbrocks run really good for street carbs when tuned. They also give decent gas milage on stock to mild builds. The bad thing about Carter/Edelbrock is getting and then keeping them tuned. It's a hit or miss sometimes. Some people swear by them others hate them. I've had carter, edelbrock and holley. I've had 3 carter/edelbrocks. 2 of the 3 were great after rebuilding and setting up. The third was rebuilt and base settings set according to the instructions. It wouldn't run right no mater what I did or who set it up. It was replaceed by my present Holley. Which is a great carb, just needs alittle fine tunning. By the way the rebuild kit runs about $40 if I remember correctly. It will have new parts that seem to wear out fast on those carbs along with instruction for tear down/rebuild and base settings to get it running. That is if you can't find instructions online.
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Senior User
Joined: May 2005
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From: Jacksonville IL
I think I can lay my hands on a new Holley 0-80457. But I stayed away from it because someone told me that Holley's are tempermental and that they are not the greatest when it comes to fuel economy. But are the best in performance. Well, that made me think that I am fighting fuel ecomomy here and so it does not make sense to get a carb that does not care much about fuel economy.
So, what you guys think about the 0-80457?
Is there a way to find out what my rear end gear ratio is? Maybe that's my problem. I know that I have some problem with my transmission. It takes a few seconds to engage into drive before I can move the truck forward. Also, there is a thud when it engages to reverse.
So, what you guys think about the 0-80457?
Is there a way to find out what my rear end gear ratio is? Maybe that's my problem. I know that I have some problem with my transmission. It takes a few seconds to engage into drive before I can move the truck forward. Also, there is a thud when it engages to reverse.
Last edited by nsaikia; May 27, 2005 at 01:53 PM.