kalli

i have my money on carb is getting too hot, vaporizing fuel.
It's a vicious circle. the carb gets hot, vaporizes fuel, running lean causing it to run even hotter. bubbles in filter near carb are telltale signs.
I'd try a phenolic spacer right under the carb and make sure the fuel lines are away from any heat source.

Gun Jam

why is it that some cars have this problem and others dont kalli?

its gonna be like a 105 out today and Im not going to have any issues I dont run a spacer either.

-Gun

kalli

could be a lot of things I guess:
half blocked radiator, half blocked block/heads (gunked up) so it can't cool properly.
Crappy waterpump, missing shoud, too small radiator, fan not effective, underdrive pulleys ... anything that gets the engine hot. if the engine is hot the heat travels to carb through intake. Maybe it's the fuel line passing close to heater hose or exhaust

I know a thunderbird that could idle from here to christmas in the desert not a bother at 650rpm. If my rpms start to drop things get hot under the hood. a bigger radiator would probably help. without the spacer my carb just gets too hot.

kalli

a miracle to me as well. I've seen cars doing that just after they get to operating temperature. Mine was very bad, but I had underdrive pulleys which caused the pump to run too slow at idle. changing that helped a lot. I guess as well underhood temperatures are a great factor. I've observed it once where a closed hood gives the problem but when you open it it normalises after a few minutes. Sometimes I suspected fuel pump and lines as well as I thought it would pull air from outside but it always seems to be coming from the carb and only when hot.

I know someone with a 460 Thunderbird (we just done freezeplugs to that car) and that would idle in the desert forever without a problem. My car on the other side still gets warm in traffic jam under the hood. without the spacer I was bubbling like a madman, but I have the steel fuel line not too far from header, so I blame that for the moment. At the moment it's not scaring me as I can control it. as soon as I rev at steady 1000 rpm temperature goes down again. maybe it's blocked radiators, heads, ineffective fans. it stumps me as well ... :-(

63Falcon

The bubbles really seem to be coming from the fuel pump. They come out of the outlet nipple on the fuel pump and flow upward toward the carb. This has really had me stumped. But I'm hopeful that we'll get the problem traced to it's source. I plan on temporarily replacing all fuel lines with clear tubing so I can trace the bubbles to their source. Already have fuel pump to carb done. Will just need to install clear tubing from tank to metal line and from metal line to the fuel pump. I may even bypass the metal line with clear tubing. Back into it on Saturday.

JMD

I could be wrong, but I think you might be chasing a ghost. I have HEARD that todays fuel vaporizes at a lower temperature than fuel from the old days, and that this is not a big deal since all new cars have fuel systems that involve RECIRCULATION of the fuel instead of the fuel laying near static in the lines until it is consumed.

I remember using a clear fuel filter when I was a kid, I was surprised that it always had an air bubble in it no matte how often I "emptied" it. I think this is the nature of gasoline.

An air bubble between the pump and filter will pass out the carb vent and is of little consequence, a large bubble in the fuel pump will cause loss of pumping action and vapor lock.

Your issue may be these bubbles, but before I started chasing these "ghosts" I would made sure points, ignition, timing, plugs, etc are right.


If your fuel lins has a hole that is admitting air it will almost certainly be above the fuel level in the tank or you would probably have small gas drips on the floor, or at least a heavy gas smell.
I have heard that the "Loadmatic" distributors are particularly troublesome.

63Falcon

All ready have been thru the entire ignition system. New points, condenser, rotor, distributer cap, coil, wires, plugs. Checked timing, compression, vacuum at manifold.

There are no gas drips or gas heavy smells.

63Falcon

I plan on dipping back into it on Sat. or Sun.

photocliff

I also think the same as JMD. Have you checked the hose clamp at the top of the tank? It could be cracked enough to be sucking air and it won't be dripping while not running. Also, even if that part of the line drains back into the tank there is pleanty of fuel in the forward lines to allow the motor to turn right over and re-prime the line.

63Falcon

Do you mean where the metal line is connected to the fuel sender with a rubber hose?