[Mgs] Mode of failure for ignition coil

[Ron Fine]

Paul,

I have a question about the coil on my 66MGB.  After a recent rebuild of the 
engine I installed a new "stock" coil purchased from Moss.  I immediately 
noticed that my electric tack started jumping all over the place when the 
RPMs got over 2000.  The car seemed to run ok.  I carefully checked the 
wires and connections, including tracing the full lenth of the white wire 
which passes through the loop holder on the tack between the ignition switch 
and the coil.  I found no obvious problems with the wire.  So,  I replaced 
the new coil with the original one which must have been in the car for many 
years and the problem with the tack disappeared.
Is seems like it was just a bad new coil or should I be looking some place 
else?
Ron