Carb leak when hot and engine off.

[PaulUK1955]

When the engine in hot and engine off, I get a few drops of fuel out of the main throttle shaft. Could just be slight wear. I assume its because the fuel expands when hot and a bit overflows into the chamber onto the butterflys and then drips out..

Thinking of lowering the float level to try to lessen the chances of over expansion when hot.

is the float level adjustable. ? i have the 4 barrel Holley on my engine. Or other ideas please?

[CSavaglio]

The float level won't likely help a leak at the shaft since even the bottom of the float is above it. That's a wear issue. The way to fix it is to pull the butterfly assembly a d have a machinist press and machine new bushings for the shaft.

[bobioknight]

As Chris said, bushing on an old carb can be worn. Mine were and caused vacuum leaks. Idle fluctuations and rough idling.

I have been experiencing fuel boiling over for for the last year or so, if what you are experiencing is like me, you drive around and turn off the engine, you look down the carb and see fuel trickling and boiling down the shafts. Also you sit at a light and intermittently your rpm's bounce, you are probably considering that your fuel is too hot and expanding in the bowl, maybe the fuel lines are too close to the engine, etc... Maybe vapor locking... Does this sound familiar? Up til two weeks ago, this was my story, let me know if it's similar to yours and I can elaborate and give you some suggestions.

[PaulUK1955]

Yep, thanks guys. Looks just like that, just a dribble once the engine is hot and off. Nothing whilst its running. comes out of the butterfly shaft ends.

Might just get an exchange carb as my one has done a lot of work. Base plate looks slightly warped as well so exchange looks best. I usually get my bits from Larrys Tbirds. Shipping and TAX is usually as much as the part costs!

Still, worth doing the job properly.

[PaulUK1955]

Also, BOB, noticed you have similar cars to me! I have a red 55 tbird, and a 2004 Jaguar XKR !

[bobioknight]

Also, BOB, noticed you have similar cars to me! I have a red 55 tbird, and a 2004 Jaguar XKR !

What's the chances of that? That's awesome. 2 great cars for sure, but I see you have the "R" quite a bit quicker....

[bobioknight]

Yep, thanks guys. Looks just like that, just a dribble once the engine is hot and off. Nothing whilst its running. comes out of the butterfly shaft ends.

After a year of driving everyone on this forum crazy with questions, new carb, hoses, vacuum lines, carb gaskets, carb spacers, intake gaskets, plugs, daily timing adjustments... You name it I was trying everything... Turns out it was two things, a dirty fuel tank, that had a rotted interior filter, you could not see the fibers in the fuel, but they were there plugging up the jets and float needles and seats. 2nd issue, my filter bowl was installed wrong, allowing it all into the carb. A simple test is open the trunk pop open the sender unit and look into the fuel tank, (please use a flashlight or cel phone camera, do not use anything with a flame) if there is anything at the bottom, you should drop the tank (very easy to do) and wash it out. Then blow out all the lines, fuel pump, all the way up to the carb with air and some carb carb cleaner.

Do you have the bowl filter, make sure you have installed the filter correct, filter first, slide the rubber gasket over the top of the filter and tighten the bowl.

That fixed my entire issue, then all I had to do was readjust the timing and idle mixture screws and it has been running great, no sputtering at lights, no fuel smell in the garage after a drive, gaining trust as I drive it further and further without issues.

Let me know if you see any garbage in the tank?

By the way do you have a vacuum gauge, a laser temp reader and a timing light?

What fuel are you running?

..... Disclaimer: I may be off base because I am a total beginner, the guys on this forum know their stuff, but at this point I Consider myself a pro "on my car"... And it sounds like you are experiencing what I have. If I am leading you down a dark path, I am sure someone will speak up.

[bobioknight]

PaulUK1955, any update on this?

[PaulUK1955]

yep, looks like the main butterfly shaft is worn as suggested. Tried to get an exchange carb from Larry tbird shop but they don't have any at the moment so will try to get it fixed locally. That's the only issue and otherwise the car runs just fine. its a 1957 carb 4 barrel.

Not sure if there is a modern Holley carb that would fit? wonder if anyone has done that?

[bobioknight]

[bobioknight]

yep, looks like the main butterfly shaft is worn as suggested. Tried to get an exchange carb from Larry tbird shop but they don't have any at the moment so will try to get it fixed locally. That's the only issue and otherwise the car runs just fine. its a 1957 carb 4 barrel.

Not sure if there is a modern Holley carb that would fit? wonder if anyone has done that?

That's great news, easy obvious fix. My original carb had the same issue, except leaking vacuum instead of fuel. I ordered the Holley carb that I attached the photo of. Worked perfectly.

[PaulUK1955]

Great, thanks for that. Did the carb fit easily, as in was there much to do to make it fit? Did the fuel line need changing etc?

Looks a good option.

[bobioknight]

Great, thanks for that. Did the carb fit easily, as in was there much to do to make it fit? Did the fuel line need changing etc?

Looks a good option.

For me it was an exact matchup, just make sure you adjust the accelerator pump, choke & idle mixture screws. Easy