Welcome to the site, Dave.  You've come to the right place for help.  While the y-block was only produced by FoMoCo in the U.S. from '54 through '64, many of us on here are still working with them in one arena or another.  Many of our members are SERIOUS motor heads.

With the advent of computers and error code read-outs, fuel injection, distributor-less ignition systems, some of today's mechanics just aren't familiar with what you have under your hood.  As an example, your 'Bird's ignition distributor's spark advance system is solely controlled by vacuum signals from multiple circuits in your '56 carburetor.  -You've got a double chamber vacuum advance unit on your distributor that has lines that come from different locations.  This method of ignition advance was abandoned by FoMoCo on the y-block in 1957.  -'56 was the last year it was used in a y-block equipped production vehicle.

Pete, Paul, Charlie, and John (Oldmics) are all steering you right.  It's time to stop what's been going on to date by those you've turned to previously for help, and go at this in a more deductive manner.  Unfortunately, it is entirely possible that something you've had done along the way WAS done incorrectly, like changing the timing chain.  Four years ago, I had a friend who got his rebuilt engine short block back from a reputable auto machine shop.  While the machining work was fine, the timing chain was installed with the timing gear marks not properly positioned for a y-block.  Happily, we spotted it before we put the timing chain cover on.  It wouldn't have run otherwise.

As Oldmics suggested, since it doesn't sound like you're into this mechanical stuff yourself, consider letting us know where you are located.  Hopefully there is a Forum member in your vicinity who might lend a hand or who may be able to recommend a knowledgeable individual or shop to turn to in your area.  Too, there may be someone near you who is a member of the Classic Thunderbird Club International who is in your vicinity and we can connect you with.  -I've got the membership roster with phone numbers and email addresses for a reference.

IF that isn't possible, we'll have to try working through this with you as to what to have checked first, second, etc.  As I've already indicated, it's only too possible that one or more of those you have paid to do work on your '56 has in fact added to whatever problem you started with.

Marvin Hill and his son Tim's business is reliable for their carburetor work on the Holley 4000s and the '57 Holley 4150s, so don't worry about your carburetor rebuild unless someones been messing with it since you got it back.

Regards,     


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Dave
Would also be helpful  to know your location so that we could refer you to local competent folks who know Thunderbird repair procedures.

Oldmics

So, 1 year and 7 months ago it broke down, you got it running, parked it, and within hours, it no longer runs well.  How old is the gas?



Lawrenceville, GA

Dave: Pete is on the  right track. It's apparent that just throwing money at it without a reasoned approach is not the answer. For instance, was any attempt made to ascertain if the fuel pump was actually delivering fuel before replacement?  And you replaced the plug wiring 3 times!!  Why?!  A reasoned approach is needed, not just desperation moves. A vacuum check would be a good place to start. And what vacuum lines weren't hooked up to what?..And the timing chain was replaced, are you sure it was installed properly? Some of the those changes may have just led to complications re the needed repair..   


Paul

Dave, First thing to do is stop doing anything. Then find out what the problem ( s) are. Do a step by step approach to identify what is wrong. Compression check. Timing check. Pull and plug any and all vacuum ports and vacuum sources on the motor. Hook up a vacuum gage to MANIFOLD vacuum and get a reading. Then share your results with the people on this site for some advice that will get you headed in the right direction. Pete

Can any one help bought our dream car 5 years ago everything was great, enjoying the car and the shows, then last year we took her out for Mother's Day and she broke down and had to have her hauled home.  We have had about 6 different people take a look and have replaced fuel pump,Timing chain, Plugs and wires 3 times, along with new points, have had the Carb rebuilt twice, (the first a local shop, and the last sent to Hill's Thunderbird Center in Ohio.  Bottom line she started ran ruff adjusted her out and was running ok.  Moved her out of the shop and she sat for a couple of hours and when went to put her away she wouldn't stay running and had to push her back in.  Everyone I talked to either say don't know or its you vacuum lines.  The vacuum lines were not hooked up when we bought her and she ran great.  Have gotten the lines ordered them from Mac's Auto.  Bottom line can't find anything that show and tell me how to install.  Not sure this would even fix our problem.  I'm about ready to take her somewhere and have the motor pulled.  Looking for any help.