carter afb: fuel disappears?

-
D

dirt wagon

Active Member
Joined
Dec 7, 2012
Messages
37
Reaction score
4
Location
new orleans
I have an older carter afb that a friend gave me. Its a 750 cfm. When left for a week or so after running the car there is no fuel in the float bowl. I rebuilt it before I installed it on the car and I have taken it apart a few times to check everything out and clean it. As far as I can tell everything looks normal. Is it leaking out and eventually contaminating the oil? The car runs great after I get gas in the carb. If it is leaking, does anyone know how I can fix it? Thanks.
 
My guess is the fuel is evaporating or boiling away is a better description.
Pull the coil wire and spin it long enough to fill the bowl. If residual heat was boiling the fuel away it will stay in a cold bowl a lot longer.
Could be all you need is a much thicker base gasket.
 
Mine does that too, both my original AFB and my Edelbrock. I do need to try a thicker gasket as Redfish suggested. Do you have stock manifolds? Check your heatriser to make sure it's opening after warm up. tmm
 
had a older carb that did the same thing after rebuild found out there are several gaskets in the kit real close just a little difference in hole spacing between base and body make sure all gaskets match the originals also check float bowels for hairline cracks hope this helps
 
It's probably the "puppy pee fuel evaporation syndrome". lol
 
if yours is Thermoquad the plugs in the bottom of the float bowels can leak fuel into the engine the only way to fix is to epoxy the plugs
 
a higher float level might help. i found i could run AFBs at 5/16 float level. i had a 1965 300 L 413 all stock run 16.00 ET. the plugs was a little lean. stock float level was 7/32. but 5/16 made the plugs color right. i know the books all say that float level will not change the amount of fuel flow. WRONG!!!!
 
After a week sitting it has evaporated, thanks to ethanol. I have a 1/2" phonoloc insulator on my avs it doesn't help, the carb is vented so after the heat of the shut down then a week sitting 2/3rds of it is gone. The holley in my other car seems to hold gas much longer.
 
EL5DEMON340 said:
After a week sitting it has evaporated, thanks to ethanol. I have a 1/2" phonoloc insulator on my avs it doesn't help, the carb is vented so after the heat of the shut down then a week sitting 2/3rds of it is gone. The holley in my other car seems to hold gas much longer.
Click to expand...

I was wondering if anyone anyone would comment on Holleys' I can see how they would be less susceptible to vapor lock problems because of the float bowls hanging over the baseplate. tmm

'
'
 
See my posts in the spacer and vapor lock threads. Didn't cure it, but it slowed it down with my old AFB.
 
toolmanmike said:
I was wondering if anyone anyone would comment on Holleys' I can see how they would be less susceptible to vapor lock problems because of the float bowls hanging over the baseplate. tmm

'
'
Click to expand...
i think the AFB/AVS is more problematic because the fuel is closer to the manifold center. Also they are aluminum body's and get hotter than the holley.
 
EL5DEMON340 said:
i think the AFB/AVS is more problematic because the fuel is closer to the manifold center. Also they are aluminum body's and get hotter than the holley.
Click to expand...
Had a look at this. A356 has an almost 60% higher Thermal Conduction rate than does Zamak (Zinc based alloy most likely close to what Holleys are made of).
Zamak: 729 BTU-in/hr-ft²-°F
A356 (Perm Mold Cast): 1160 BTU-in/hr-ft²-°F
 
If you buy a spacer you can use a file or hacksaw blade to serrate its vertical faces. VVVVVV will more than double the surface area improving its heat sink characteristic.
 
As I've said in the other threads, I believe that the ~1/8" plate is the better bet for combating fuel bowl boiling while under way. On a hot shut-down I don't think that there is much that you can do. The plate will shield the AFB bowls from heat radiating up off the engine and that may buy you enough time for the engine to cool before all of the fuel is boiled off.
 
I have the same issue. The carb was rebuilt by a professional, not me. The carb before the rebuild looked as though it had red mud in the dry carb. The guys in Texas who rebuilt may carb told me this was caused by ethanol used in gas today. My car is in the garage and never runs over 30 minutes as I am still restoring her. I'm not sure I buy the heat being the issue. I would like more info on where it may be leaking internally. I just don't understand. I had a friend who had a new Holly which would do the same thing. I wonder if the issue is the ethanol.
I am no professional, and am certainly not discounting any of your ideas, Just seeking an answer to a problem. I had no idea the problem was as widespread as it seems to be. Maybe changing to a non-ethanol fuel would help. Someone local who builds and races drag car said he uses a fuel stabilizer in his fuel to help with the problem, maybe a thought.
 
todays gasoline is formulated for fuel injection system that is not open to the atmosphere...it is more prong to evaporate

the AFB carb accelerator pump well is sets above the floor of the fuel bowl...and the fuel evaporates from the bowl and pump well...the pump well will go empty before the bowl is empty...then you have no accelerator pump squirt.....and no pump squirt...no start

and the fuel bowl on an AFB are kind of small too.....put a small electric pump on car....issued solved...

my 73 Duster with eddy afb can sit for weeks...and I actually have to squirt gas into the engine to get it to fire....
 
Tadams said:
I wonder if the issue is the ethanol.
Click to expand...

Today's gas is crappola.

I ran a Thermoquad for a while and the gas would just disappear, I thought it was leaking too.

After putting about an inch and a half of gas in a spray can cap and letting it sit on my workbench I'm convinced it was evaporating.

I put the gas in the cap and let it set for less than 24 hours, it was in the mid to high 80's and somewhat humid.

I came out to the garage the next day and the cap was bone dry. Either a mouse drank it, or it evaporated.
 
Concur with the comment that today's fuel is made for EFI and those still with carbs are stuck. I came to that conclusion ~20 years ago when driving the carb'd car (AFB and several different Holley's). Really wouldn't surprise me if the ethanol is aiding and abetting in making this even worse.

This is why I think that duplicating the EFI fuel system, as much as possible, is worth doing. Increase the supply pressure with an EFI pump mounted either in the tank or close to it and down low. Use a bypass type fuel pressure regulator (FPR) with a return back to the tank. If I were staying with a carb my by-passing FPR would be a whole lot closer to the carb than it is now, make the line from the FPR to the carb as short as possible..
 
You must log in or register to reply here.
-

Back
Top