MG Car Repair: 1977 MGB Fuel Issue?, zenith stromberg, vacuum test

Question
Just bought a 77 B that had been secured in a storage building since 1991.  The usually nickel and dime stuff has all been done including, oil, plugs, wires, checked the compression which was consistent in the high 150's all four cylinders. Starts, warms up and both fans work. Oil pressure above 50 lbs, as soon as throttle is above idle. The much-maligned Zenith Stromberg carb seemed to choke up and idle down as it should with a bit of erratic but nothing expected with it.  I got it home drove about a mile and it did fine.  Later the next day I fired it up and got about a mile from house and it just died.  It would fire up and take gas sitting still and sound great as soon as I dropped the clutch it would die again.  Is this fuel or possibly fuel pump related?  Any suggestions on where to start?  Weird how it happened so instantly and how it will idle and sit without a load on it and run so good. I did the nickel/dime stuff, (new battery, plugs, fluids. fuses, etc.) and was pleasantly surprised when most everything worked.  Thanks

Answer
Hi Chris,
You need to see which has been lost, fuel or fire at the time of failure. Compression will not come and go. Fire and fuel can.
Fuel is the most likely so you should look there first. The "B" with a single Stromberg is very lean and is thus susceptible to several items like the loss of the oil in the top damper of the carb will make it so lean on a quick throttle opening or a load applied. Also, if the original air filter was restrictive on purpose and is required to apply enough choking action on the carburetor that if it is too open to air the carb will be very lean and will not handle load or a quick throttle opening. One other possible is a partially stopped up exhaust system. A preliminary test would be to run a manifold vacuum test at idle and slowly open the throttle to see if vacuum goes away. If so, you should run a exhaust back pressure test. Don't forget a fuel pressure test at the time of failure also.
Let me know,
Howard