MG Car Repair: non smog head, vacuum leak, lean condition

Question
I had a crack head on my 79 mgb so i found a early non smog head had the valve done. The problem is now i cant keep car from sputtering and rough idle change the plugs i also have a Weber downdraft carb on it. It does not have any power cant drive have not move timing runs so ruff need help

Answer
Hi Adam,
Did the engine ever run right with the Weber on it? The fact that you used a non smog head has nothing to do with it unless you have a intake manifold leak or such.

You need to start from scratch on diagnosis. This is what I have to do when a car is brought to me in a dealership with your complaint.

First and most important is a compression test. (Throttle open and at least 4 or 5 revolutions of the engine. You should see at least 125 to 180 PSI on all cylinders with little difference between each cylinder.)

Set the timing ACCURATELY to factory specs. Then put the timing light on the coil wire and hold the trigger down and watch the flash of the light. even a slight miss in ignition will show in the flash. The flash should be a smooth steady flash. A scope would be much better if you have access to one. Be sure to either clean the plugs or replace them.

When the engine is warmed up and idling and notably rough remove the air filter and cup your hands over the intake with your fingers spread so as to let plenty of air in. Then start very slowly closing off the air supply a little at a time and note the engine response. It should start slowing down and getting rougher until it quits. If at any time it smoothes out or speeds up then you for sure have either a vacuum leak or a very lean condition.
Let me know,
Howard