I took my 65 comet into town today and after shutting it off it wouldn't start. I had to pour gas into the carb to get it to fire up. When I got home it stalled in the drive and wouldn't start again. I lifted the hood and gas was coming out of the carb. When I say coming out it was more like boiling out. there is a heater hose that runs through the base of the carb and it was quite hot. Could this be causing the fuel to boil? The carb looks brand new ( I just bought this car ) as is everything else. I thought of a sticking needle valve but the car is not getting fuel down to the cylinders it seems to just be evaporating away. I was thinking of bypassing the base heater line and just hook them together so they wouldn't be heating the base of the carb too much. Any info would be greatly appreciated.
Carb problem
- Thread starter mannella
- Start date
Marine05
Well-known member
Sounds like you hit the nail on the head. If it looks like it is boiling out, chances are it is. If its hot where you are, im assuming it is, get rid of it. Ur just adding heat to the already hot fuel. I've never really liked the base heaters. If you have an adequate cooling fan, you shouldn't need one. Drop and kick that SOB. Good luck
Have to say I disagree with marine 05, the heat problem comes from the carb sitting directly above the exhaust manifold, I still run the coolant plate under my carb, the coolant is around 200 degrees and that is much less than the exhaust temp. The autolite 1100s seem to be extremely sensitive to heat, I had problems with mine boiling the fuel especially after shutting down in hot weather because when the coolant stopped flowing the carb soaked up the heat from the exhaust and engine, it would start hard and run very rough til the system had time to cool things down. The last time I tore down the carb I was careful to set the float high enough to keep the bowl as full as possible and this seems to have cured the problem. Much info is here on the forum, some people go to extremes such as fabricating heat shields, wrapping fuel lines with heat shield (which is probably a good idea). I just tried to keep my metal fuel line away from hot spots and keep the carb as full as possible and I guess I got lucky. You say your carb looks new so it's most likely a rebuild and I've heard that a lot of them are of questionable quality, your float may be set too high and not seating the needle valve tightly, what kind of filter are you running, if you have an old fuel tank it's hard to keep debris out of the carb, I ended up replacing my tank after clogging two or three stock filters and watching the gunk and rust build up in a see through aftermarket replacement (which by the way doesen't filter as well as the stock bronze filter). Do a search on "vapor lock'" to find more opinions on the problem, it's been addressed here many times! Good luck! 
Thanks for the info. I have a clear see through filter and I believe there is one on top of the fuel pump, so I don't think dirt is the problem. I took the carb apart and the float is set at the max height from what I could tell. I push the floats down a little to maximize pressure on the needle valve. I let the car idle at max temp and there was no flooding. I'm going to take it for a run tomorrow and see what happens. It wasn't that hot here today so I'm not sure if its a boiling problem or just the needle valve not shutting off the fuel supply
Make sure your exhaust is flowing properly. My car did that when I first bought it and I eventually found it was because one of the exhaust pipes was kinked and blocking most of the flow. That creates lots of extra heat up front. If its been sitting it could be critters nesting.
8) i also agree that you have a fuel boil problem, and i agree with sixpony that the problem comes from the exhaust manifold. remember that the carb sits right over where not only do two exhaust ports exit at that point, but the other four cylinders also feed that hot spot. at this point you have two options;
1: swap the exhaust manifold for a header
2: fabricate a heat shield to block the heat and insulate the carb.
even if you install a header you may have to fab a heat shield anyway as some still have fuel boil issues.
1: swap the exhaust manifold for a header
2: fabricate a heat shield to block the heat and insulate the carb.
even if you install a header you may have to fab a heat shield anyway as some still have fuel boil issues.
Ok what I don't understand is was this a problem from day one with this setup and if it was I would assume that ford had some sort of fix for it. Having said that would bypassing the heated base help? I have looked at how to shield the carb but can't come up with a workable plan. I thought of making a plate that would go under the carb and extend out to the back of the engine working more like a heat sink and a shield. I've driven this car a few times and had no problems, but now all of a sudden its giving me grief. I took the carb apart today twice. the fuel level in the carb looks like its where it should be, just above the accelerator pump housing. there seemed to be a lot of fuel pressure when I loosened the fuel line at the carb. I'm sure that once the nut is released that there should just be a second or two of fuel squirting out but I seemed to get a lot of fuel at a fairly high pressure. Don't know if this is significant or not. I'm going to take the car to town tomorrow if its not raining and see if it acts up again, I will post what ever happens. Thanks for the input.
Where do you live? Hot area or not? I live in SoCal where it can get very warm. I disconnected the heater hoses to the base plate and have never had the fuel boil problem. OTOH, I have headers, not the stock exhaust manifold.
The heated base plate is primarily to keep the carb base warm in the winter. However, it ALSO maintains a constant or at least consistent temperature (ca. +/- 200*) at the carb mount. When you stop, the heat travels up through the plate to the carb. Then your fuel could boil. You might look to see if the heater core is plugged. That would cause the coolant to NOT flow and defeat the temp maintenance aspect of the thing. (The hoses could be hot from the radiant heat and not from the coolant flow. They get hot but not too hot to touch if they are flowing properly.)
Like I said, I have exhaust headers. They are much lighter metal than a cast exhaust and the heat dissipates more quickly.
All this assumes that you have a fuel boil/heat sink problem. It could be other things too, like the choke sticking closed or the needle valve failing to open at first. Try blipping the accelerator three or four times before you crank it when warm. At least you'll get a shot of gas into the carb throat.
The heated base plate is primarily to keep the carb base warm in the winter. However, it ALSO maintains a constant or at least consistent temperature (ca. +/- 200*) at the carb mount. When you stop, the heat travels up through the plate to the carb. Then your fuel could boil. You might look to see if the heater core is plugged. That would cause the coolant to NOT flow and defeat the temp maintenance aspect of the thing. (The hoses could be hot from the radiant heat and not from the coolant flow. They get hot but not too hot to touch if they are flowing properly.)
Like I said, I have exhaust headers. They are much lighter metal than a cast exhaust and the heat dissipates more quickly.
All this assumes that you have a fuel boil/heat sink problem. It could be other things too, like the choke sticking closed or the needle valve failing to open at first. Try blipping the accelerator three or four times before you crank it when warm. At least you'll get a shot of gas into the carb throat.
I live in central Ontario Canada. The heater is giving off heat when turned it on but I would assume that when its turned off there shouldn't be any coolant going through the heater core. When the engine is cold I don't have a problem starting the car, its after a run on the highway and I turn it off, after a few minutes it won't start unless I pour a bit of fuel down the carb. This happened the other day and after I got it going and brought it home is stalled pulling into the drive and when I lifted the hood gas was coming out of the base of the carb. I know they like to have header pipes all the same length but is this critical? will the performace of the car be affected if one was a little longer than the other?
Look through the string about 'phenolic spacer' or some such. Phenolic at any rate. There is a lot of info about insulating spacers that also includes gaskets and such.
And yes, the coolant will still be flowing through the heater core even if the heat is not on. The fan just doesn't push air past it and the warm air flow is baffled off. If you get in an overheating situation some time, throw the heater on max an you will have that much more heat dissipation.
And yes, the coolant will still be flowing through the heater core even if the heat is not on. The fan just doesn't push air past it and the warm air flow is baffled off. If you get in an overheating situation some time, throw the heater on max an you will have that much more heat dissipation.
On a lot of cars that I have own (old ones ) the water didn't go through the heater core. A good example is the 69 Lincoln that I owned it had a water valve that was operated by vacuum and it shut off the water supply. I don't see anything resembling such a thing on the comet but the heater hoses go into the firewall so there could be something there. I'm going to by pass the base plate then I'm going to run a rad hose from it up to the front of the car by the rad and see if I can get some cooler air flowing through the base plate. I realize it won't be a lot but it will be from one extreme to another will let you know how it works. If it doesn't cure the problem then I will go to the gasket suggestion and if it is still a problem I will try and make a set of headers.
HARVEY LIGHT
Well-known member
Back in 1968 (when I first caught the Falcom/Comet bug) we lived in Las Vegas and my budy's Comet used to do this very same thing when the weather was hot enough. We used to cary a cooler and a jug of water in the car. The cooler had some ice things - the reusable kind - which we'd use to cool the carb. The wate was to cool ourselves 
.
NOW I know way much more about our little wonders and still have one for my fun. Seriously - I'd follow up on both a spacer and checking about the heater core being crudded up. (In Vegas we hardly ever needed the heater so it was shut off and eventually corroded on my pal, dumping coolant on the floor)
. NOW I know way much more about our little wonders and still have one for my fun. Seriously - I'd follow up on both a spacer and checking about the heater core being crudded up. (In Vegas we hardly ever needed the heater so it was shut off and eventually corroded on my pal, dumping coolant on the floor)
66 Fastback
Famous Member
Seeing as how you are in Canada, you may want to keep that coolant line hooked up for the winter weather.
You might check your timing just to make sure that it is correct and not contributing to th high exhaust temps that could be causing your fuel boiling. I would not think fuel boiling would be as common up in your area.
If the timing is retarded or the Load-o-matic distributor is not working, the exhaust temps will climb. I have had seen cherry red exhaust on my motorcycle when the timing was messed up.
Doug
You might check your timing just to make sure that it is correct and not contributing to th high exhaust temps that could be causing your fuel boiling. I would not think fuel boiling would be as common up in your area.
If the timing is retarded or the Load-o-matic distributor is not working, the exhaust temps will climb. I have had seen cherry red exhaust on my motorcycle when the timing was messed up.
Doug
sixpony":2dgl6t5l said:Just out of curiosity I'd like to hear some input from the guys running the two barrels, direct mount or adapter, as far as I have seen the little autolite 1100 is the only one that has this problem. What about the holley 1bb?
8) i put an autolite two barrel carb on my 66 falcon, and to my knowledge there has been no further problem with fuel boil. i have yet to do that with my 64 falcon, and that car has a fuel boil problem, eithe r with the autolite 1100 or the equivalent holley one barrel carb. the two barrel install used an adapter.
as for the heater core, it is a constant flow design core. the higher end cars were the ones that got a vacuum cut offwhen the heater was not in use.
the carb on this car is a holley one barrelsixpony":v6p8k5i8 said:Just out of curiosity I'd like to hear some input from the guys running the two barrels, direct mount or adapter, as far as I have seen the little autolite 1100 is the only one that has this problem. What about the holley 1bb?
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