I'm having trouble getting my 1968 142S running after it sat for 15 years. Here's some background on it:

B18 with SU HS6 carbs
160k miles
~175 compression, except for one cylinder at 155
Timing set to 16 BTDC
New cap, rotor, plugs, wires
New battery
New fuel pump
Valve clearance within spec, but valve #4 looks to have a worn cam lobe
Car has a rusted out muffler and a leaking manifold to header gasket, but that shouldn't affect my current running issue


Right now, it will fire up and idle smoothly for about a minute. After that, it dies, as if it's starving for fuel. If I start it again, it'll run for a few seconds, then dies again. However, I have discovered that I can keep it running by pulling the choke in and out. It's not the position of the choke, but the actual movement of the jet that is keeping it running. The faster I move it back and forth, the smoother it runs. If I leave it in either position for more than a couple seconds, it dies.

It seems to get better as it gets hot. I have tried adjusting the jets leaner or richer, but it doesn't seem to change the fuel starvation.

I'm thinking that it could be a vacuum leak at the carb throttle plates, since I wasn't able to press new bushings in when I rebuilt them. The throttle shafts have some play. My theory is that the carb body is losing vacuum enough to suck fuel up the jet, but moving the choke physically pushes fuel ingot he carb throat, where it's able to get sucked into the motor. Is the a ridiculous thought?

The brand new fuel pump is filling the bowls with fuel, and the jets are brand new and not clogged. The ignition is all new, and I don't suspect any issues there.

Any ideas? I really want to get this thing back on the road!