MG Car Repair: Mgbgt, engine tone, cam shaft

Question
QUESTION: Engine tone uneven. Removed rocker cover and found that a pushrod? Was wobbly and adrift of the  ball at the base of the rocker arm. Slid back arm and removed push rod in tact but noticed what appears to be scratches at the base. Cannot adjust the slotted bolt to contact the cam shaft. Engine ran smooth to start with.
Can you please advise me? Had a full rebuild about 3k ago but time has proven that the co that did the work were not skilled or honest!

ANSWER: Hi Damian

Sounds as though there is a problem with one of the rockers, or a valve has stuck open, or you have a bent pushrod.  

1) Can you manually rock the rocker or is it stiff?  It should have virtually no resistance to rotation.  

2) Look at the valves.  Is one of them lower than the rest and never coming fully up like the other seven?

3) Extract the pushrod and roll it on a flat surface.  Does it look straight?

If you have access to a compression tester, put the engine back together and check the compressions.

Let me know how you get on.

---------- FOLLOW-UP ----------

QUESTION: Thanks Barrie,
Rocker arm rotates freely until contacts the top of the valve? opposite.slides against the spring freely. That seems fine to a complete novice. Rod does not appear bent. Probably 25mm frm adjuster ball. Could valve opposte be stuck? Should i be able to move it by moving rocker arm? Engine ran even at first.

Answer
There are several possibilities.  It is difficult for me to diagnose.  Rocker sounds to be OK.  No, you cannot open a valve by hand, it should be held shut by a spring (which is stronger than you are).  

Does the troublesome valve look to be the same height as the others? (ignoring those that are opened by other rockers).  

Sounds like a stuck valve to me.  If you have an unleaded head, it could be that one of the hardened valve seats has come adrift.  

Either way, it requires the removal of the head to fix and it shouldn't have happened on a reconditioned engine after 3,000 miles.  

It sounds like a manufacturing fault, unless you have caused it by running the engine without oil in the sump or without water in the radiator.  If these guys are really dishonest they could try to blame you, so check the oil and water levels before you get in touch with them.