MG Car Repair: 1500 mg midget, smooth flat surface, pushrod

Question
my mg push rod has jumped out of tappets why

Answer
Hi Andy,
A pushrod can't jump out of a tappet (lifter) but it can jump out of a rocker arm. Is that what you mean?
If so there are several reasons that a pushrod will jump out of a rocker arm.
A bent pushrod will do that. To test for a bent pushrod remove it and role it across a smooth flat surface. It will show if it is slightly bent.
An adjusting screw that came loose and backed out will cause it to jump out.
A sticking valve will cause a pushrod to jump out.
A broken or weak valve spring will do it too.
Over reving the engine will do it too.
A broken rocker arm can do it.

All of these need to be examined closely as it is possible for more than one of them to be the cause.
Howard