MG Car Repair: engine valves, spark plug wire, faulty valve

Question
How can I tell if I have a bad valve on a 1978 MGB4

Answer
Hi Jim
The best way to check for a faulty valve is to do a compression check.  You will need a special gauge for this.  It is the sort of thing that a competent garage could do in 5 minutes at minimal cost.  

If you want do do a quick check, try removing one spark plug lead (wire) and then running the engine.  Be careful not to get a shock from the spark plug wire.  It is usually cylinder number 3, so start with that one.  If a valve is faulty, that cylinder will make no difference to the rough running of the car, whereas if it has good valves, it will make the roughness much worse because you will now be running on 2 cylinders.  Don't immediately assume it is a faulty valve, it could be a faulty spark plug or a faulty plug wire.