carb problems.....???
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Freshman User
Joined: Mar 2012
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carb problems.....???
Hello all. Its been awhile since i was here last. My 68 F250 had sat for two years and is now my daily driver. Since I got it back on the road I have been doing necesary repairs over the last month. Has a 390 eng, autotrans.I have replaced plug wires with Accel 8mm wires, repl the stock ign coil with Accel 40,000v coil,new autolite 45 plugs gapped at 35 , repl exhaust system and mufflers adding a cross H pipe and rebuilt the autolite 2100 carb. Repl fuel pump and fuel filter,air filter. And it has Pertronix kit instead of points.
The problem i seem to be having is one day i start her up and she runs like a champ.After it sits a couple hours to a day it runs ruff. I checked timing its @ 10*.
Am I missing something here? Is there anywhere to get a NEW 2bbl carb? thanks in advance for any helpful info.
The problem i seem to be having is one day i start her up and she runs like a champ.After it sits a couple hours to a day it runs ruff. I checked timing its @ 10*.
Am I missing something here? Is there anywhere to get a NEW 2bbl carb? thanks in advance for any helpful info.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
You can buy remanned carburetors like the 2100 but they are pretty spendy for what you get and the quality of the rebuild can be suspect.
One diagnostic and tuning aid that is very useful is the mechanics vacuum gauge. They are cheap too. Oftentimes carburetors get blamed for ignition problems.
But make sure that the fuel level in the bowl is at spec at all times under all conditions. The "bench setting" or dry float level is only a ballpark adjustment, the actual fuel level in the bowl needs to be checked on level ground after running a few minutes. Too low and it will be starved for fuel at highway speeds, too high it will flood out. Either will affect jetting etc. A loose or bad power valve will let fuel leak into the manifold etc,.
One diagnostic and tuning aid that is very useful is the mechanics vacuum gauge. They are cheap too. Oftentimes carburetors get blamed for ignition problems.
But make sure that the fuel level in the bowl is at spec at all times under all conditions. The "bench setting" or dry float level is only a ballpark adjustment, the actual fuel level in the bowl needs to be checked on level ground after running a few minutes. Too low and it will be starved for fuel at highway speeds, too high it will flood out. Either will affect jetting etc. A loose or bad power valve will let fuel leak into the manifold etc,.
Posting Guru
Joined: May 2001
Posts: 1,395
Likes: 4
From: Cupertino
I agree with pretty much what Ted said above. You have done a bunch of "rule out" items.
The 2100 is a simple carburetor, quality kits widely available. The parts guys will be in soon.
Remans are suspect. Do it yourself and wreck a Saturday morning. But you get to keep the same jets.
If your problem is after the engine is sitting, you might take a look at a spacer and gas boiling problems. But first, if I were you, I would rebuild the carb
Semper Fi
The 2100 is a simple carburetor, quality kits widely available. The parts guys will be in soon.
Remans are suspect. Do it yourself and wreck a Saturday morning. But you get to keep the same jets.
If your problem is after the engine is sitting, you might take a look at a spacer and gas boiling problems. But first, if I were you, I would rebuild the carb
Semper Fi
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Thanks for the replies. I have read that the float shold be wet set at 13/16 from the bottom of thebowl to the top of the float. Then i heard from a parts store set it at 1/4" from top of bowl to top of float also heard to set it at 7/8". i have tried all of them. the part that i am about that i took the orig carb off took to a rebuilder got it back and didnt check it right away two weeks go by go to put it on and didnt see the punch marks i put on different parts of it so i would know it was mine. called them up ask where my carb was "you picked it up two wks ago" Needless to say my orig carb is gone. I just reuilt the carb AGAIN two days ago. Repl power valve,accel pump and gaskets but not the gasket under the spacer block. I will do that tomorrow.
about that i took the orig carb off took to a rebuilder got it back and didnt check it right away two weeks go by go to put it on and didnt see the punch marks i put on different parts of it so i would know it was mine. called them up ask where my carb was "you picked it up two wks ago" Needless to say my orig carb is gone. I just reuilt the carb AGAIN two days ago. Repl power valve,accel pump and gaskets but not the gasket under the spacer block. I will do that tomorrow.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
This is why you need the specification for your engine, they differ a little bit. You are getting information third hand. All the Autolite and Ford docs are available for download. The confusion stems from numbers that are similar and terms that are similar. Float height is one thing, Fuel height is another. For example my 292 specifies in the manual 21/32" float height measured from the bottom of the carb bowl to the front part of the float. This is a ballpark setting, it may end up perfect, but it might not, too. Have you replaced needle and seat?
The fuel height (which is what matters) needs to be 29/32" from the top of the carb to the surface of the fuel. None of this trivia may be the issue, but setting up a carb can be tricky if something isn't set right upstream, it will never run quite right downstream.
The fuel height (which is what matters) needs to be 29/32" from the top of the carb to the surface of the fuel. None of this trivia may be the issue, but setting up a carb can be tricky if something isn't set right upstream, it will never run quite right downstream.
Hotshot
Joined: Oct 2002
Posts: 18,488
Likes: 22
From: The Big, Oregon
Does it continue running rough or does it clear up after it's been revved a few times? If it clears up then likely it's boiling gas over into the intake, but if it stays running rough it may have debris constantly getting into the carb.
If you are running a heated spacer, then you should consider bypassing it for warmer weather. Adding a ball valve in the circuit works as well.
Otherwise, adding a phenolic spacer usually helps keep the carb a bit cooler. Also make sure if the exhaust heater valve is still present that it opens properly.
If you are running a heated spacer, then you should consider bypassing it for warmer weather. Adding a ball valve in the circuit works as well.
Otherwise, adding a phenolic spacer usually helps keep the carb a bit cooler. Also make sure if the exhaust heater valve is still present that it opens properly.
Hotshot
Joined: Mar 2013
Posts: 14,255
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From: Phoenix, Az.
You changed the coil to a Accel? I believe those are not external resistor type. To use one of these you would have to delete the pink resistor ignition wire and replace it with regular non-resistor wire. So the coil gets full 12V all the time. Does your coil or it's box say "for external resistor" on it?
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Laughing Gas
Joined: Mar 2013
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From: Garner NC
What kit did you use on the carb? Did you check the fuel bowl on the pump to see if there was junk in it? Pop the top off the carb. Use a bright flashlight and look in the fuel bowl. See any brown dust or other junk in there?
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Lead Driver
Joined: Aug 2003
Posts: 7,592
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From: **** hole San Jose ca.
Kind of sounds like a vacuum leak to me. Have you checked the dizzy vacuum advance an it's hose. And if you have power brakes check it's booster hose vacuum. Hoses will spilt many times on the under side where they can't be seen.
Also if auto tranny check the vacuum at rear of manifold and the little modulator rubber hose for leaks.
Orich
Also if auto tranny check the vacuum at rear of manifold and the little modulator rubber hose for leaks.
Orich
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FordSix it clears up after it runs for a couple of minutes.But if i drive a short distance and turn it off and it sits anywhere from a couple of minutes to an hour it runs rough again.And I looked at the air cleaner and it looks like the flap is missing a spring.
Jefffafa i will check today about the resistor for the coil. Rasputin carb was clean no debris. And orich all vacuum lines have been replaced. For the oil breather caps I know one has a hose going to the air filter and then the one on the left bank goes from the pcv to the carb base is that correct? I have seen the one to the air cleanerbut not both having hoses.
Jefffafa i will check today about the resistor for the coil. Rasputin carb was clean no debris. And orich all vacuum lines have been replaced. For the oil breather caps I know one has a hose going to the air filter and then the one on the left bank goes from the pcv to the carb base is that correct? I have seen the one to the air cleanerbut not both having hoses.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
It runs rough after sitting a while, and then clears up after a couple minutes is the key, focus on that. Sounds like it's leaking past the power valve for some reason. What do the plugs look like?
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Heat soak carb does what your saying also.
My in-laws 70 was doing the very same thing so removed the carb base heater plate and fixed that carb gas boiling over and in to the intake throat.
I remove the air filter cocked a small mirror so we could see down the carb after shouting the engine off. 17 minuets later we heard gas bubbling an looked to see it dripping.
Orich
My in-laws 70 was doing the very same thing so removed the carb base heater plate and fixed that carb gas boiling over and in to the intake throat.
I remove the air filter cocked a small mirror so we could see down the carb after shouting the engine off. 17 minuets later we heard gas bubbling an looked to see it dripping.
Orich
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Ok i've been down sick a couple of days. I checked the coil and it says its a accel universal doesnt say anything about resistor. The carb does have a carb spacer with a heater hose going in/out of it. And at one time I did hear some noise coming from the carb. Does the carb need a heated spacer? Can i mount the carb to the intake w/o a spacer? The old plugs had normal signs of wear, but i havent removed the new ones to look at them.