vacuum leak?

[TMcManus]

Have a 56 and trying to get it running smoother. Carb already rebuilt 1 yr ago. Problem.. engine chokes itself out at higher RPMs, not always but frequently. I'm sure it's not the carb. There's a fuel sending unit, electronic relay or something like that w/in the line just beneath the drivers door that doesn't seem to be stock item and I don't know if it's working right. Also, vacuum line that runs from right side of carb to right side exhaust manifold needs to be repleaced. What is this line, and could this be adding to problem? I've looked through HQ parts books and can't find the vacuum line photos or parts list.

Just starting as hobby, thanks for the help!

[bjwardsd]

There are 2 possibilities. One is that there may be a vacuum leak at the intake manifold. Start the engine, warm it up, and spray starter fluid around the entire perimeter of the bottom of the intake manifold. If the engine cuts out, you have a vacuum leak. Also your distributor may be shot. Put a dwell meter on the distributor and if the dwell wanders all over, your distributor needs to be rebuilt (about $250.00).

I have had both problems in my '57 T-Bird.

[C Prange]

Are you sure that it chokes out and is not starving for gas? If during restart you treat it like its flooded and it smokes on restart, it is choking out. If it just needs to crank to refill carb bowl, it is starving. The item below the driver door is probably either an additional gas line filter or someone has installed an electric inline fuel pump in addition to the mechanical one. If it is not working properly, it could be cutting off your gas. The line going from the carb to the right side manifold has nothing to do with vacuum. It is merely a heat tube, which heats the carb and turns off the choke. If it is severely plugged, no heat is getting to the carb and your choke will have to rely on manifold heat coming up from the engine to shut off the choke. This could also make your vehicle flood out, but unlikely. It sounds to me like either a gas starvation problem, as it happens at high RPM, or like the previous reply said, you are loosing vacuum, which is used to open the choke up.