[Mgs] Intermittent miss

[Peter Schauss]

My 1980 MGB has developed and intermittent miss.  This morning it started
and ran fine until I had gone about 5 miles on the parkway.  When it began
to cut out, the tachometer needle took a nose dive toward zero.  At one
point it cut out so badly that the engine stopped completely and I had to
pull off of the road.  It started immediately, however.  

Given the behavior of the tach I believe that the problem is on the primary
side of the ignition possibly the following components:
- the connections at the fuse block.
- the ignition relay
- the primary side of the 
- the electronic ignition amplifier (I have the CEI system with the
amplifier mounted on the fender.)

I have tentatively eliminated the fuse block connections and the relay
because the gas and fuel gauges both continued to work when the engine
started to miss and they are on a circuit which is fed by the ignition
relay.

That leaves the coil and the amplifier both of which are original.  So my
questions:

- When the coil fails when it gets hot is it the primary or secondary
winding which fails?
- Would a failing electronic ignition amplifier cause symptoms like this?

Keep in mind that this car has a ballast resistor in series with the coil
for normal running and that when the starter is energized the coil gets the
full 12 volts.

If the problem is in the amplifier I have three options:
- replace it with a stock amplifier
- get the Petronix insert for my distributor
- replace the distributor with a Petronix

Which do you suggest?

Thanks,
Peter Schauss
1980 MGB