56 tbird fuel problem?

[steveLH]

My tbird, with the 312 engine, 1956 model, with original carb, runs perfect when first started, but after a 25 to 30 mile drive begins to hesitate badly. Acts like a fuel problem, I've put a new filter on, didn't help. If you keep driving, it seems to get better, but nothing like when you first start it. Plugs are new, and it's not really like a misfire anyway. Hoping someone out there has run into this before
Thanks, Stevelh

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[mr4speed]

Steve you.ve probably tried this but try using a healthy amount of Marvel Mystery Oil in the gas. My brother has a 56 and swears by it.

 

[Dale Leonard]

I had a problem similar to this on a 1961 Ford 6 cyl. Over time it kept slowing down in speed and it was the condenser in the distributor. It was breaking down with heat. How old are your spark plugs as they can be breaking down also.
The Marvel Mystery Oil works great in the engine oil as it will clean out the lifters and quieten them down. Works great in the gas also. Have used it for many years.

 

[zeroroadkill]

Read my thread on fuel delivery problems.
1955 Gas tank pressure?

Could be:
1. Fuel pump failing
2. Crud in the tank (did you see any crud in the filter bowl when you changed the filter?)
3. Vapor lock (if hot days) where is the temp gauge when it fails?
4. Vent your gas cap. There is a PDF in this forum (Doug7740) of how to trim the cap gasket to prevent it from causing a vacuum in the tank thus making it harder for the wimpy fuel pump to suck fuel. Not sure if the '56 has a vent tube in the tank like the '57, but my '55 doesn't. See attachment.

Does it hesitate after a hard throttle? Mine would, turned out the fuel pump couldn't keep up with demand. I went through 4 replacement pumps, all POS! Finally put on an electric pump, problem solved.

Good Luck

 

[thessler]

I actually had the same problem. New fuel filter and pump no improvement. I rebuilt the carburetor, really took my time and did it right. That made it run much better and the problem not quite as bad but it was still there. Tossed the carb and put on a modern holley, runs like a champ.
Bottom line, I never fixed the problem or figured it out. I basically threw it out.
Good luck, Tom

 

[steveLH]

Steve you.ve probably tried this but try using a healthy amount of Marvel Mystery Oil in the gas. My brother has a 56 and swears by it.

yes, seafoam and marvel mystery oil. Both are very good products, thank you for the suggestion.

 

[steveLH]

Read my thread on fuel delivery problems.
1955 Gas tank pressure?

Could be:
1. Fuel pump failing
2. Crud in the tank (did you see any crud in the filter bowl when you changed the filter?)
3. Vapor lock (if hot days) where is the temp gauge when it fails?
4. Vent your gas cap. There is a PDF in this forum (Doug7740) of how to trim the cap gasket to prevent it from causing a vacuum in the tank thus making it harder for the wimpy fuel pump to suck fuel. Not sure if the '56 has a vent tube in the tank like the '57, but my '55 doesn't. See attachment.

Does it hesitate after a hard throttle? Mine would, turned out the fuel pump couldn't keep up with demand. I went through 4 replacement pumps, all POS! Finally put on an electric pump, problem solved.

Good Luck

 

[steveLH]

I had a problem similar to this on a 1961 Ford 6 cyl. Over time it kept slowing down in speed and it was the condenser in the distributor. It was breaking down with heat. How old are your spark plugs as they can be breaking down also.
The Marvel Mystery Oil works great in the engine oil as it will clean out the lifters and quieten them down. Works great in the gas also. Have used it for many years.

Plugs are new, could be a condenser , leaning more toward a pump or new carb
Thanks, Stevelh