I am running a few days behind on the digest so if someone has already
brought these issues up then feel free to ignore me.
Mike, I am not at all surprised that the ground wire melted on your
radio. Unlike the power side, the ground side of your car is a
"distributed system." In other words, any isolation between different
components is by chance, not design. When your cut your big ground
cable with the switch, apparently the current found a way back through
your radio and its ground wire. Putting a bigger wire there will only
increase the risk of damaging your radio and may make your ground cut
out completely useless. Many MGA owners have experience a similar
situation when the motor ground strap breaks (or is left off after a
rebuild- not that I have any personal experience, mind you) and the car
turns over slowly while the choke cable gets hot. I expect that the
small wire on your fuel pump died for the same reason. Is the fuel pump
ground also attached on the battery side of the cutout switch?
Personally, I would put the cutout on the hot side and run a fused,
always hot line to the radio memory. If you stick with the system you
have, put a low current slow blow fuse in the radio constant ground.
Another alternative is to put a small circuit breaker in parallel with
the cutout switch. That way if someone plays with your car without
closing the switch all you lose is your radio memory. If the memory is
a low current drain and not too voltage sensitive, you may even try
putting a 500 ohm 1/2 watt resistor in series with the device or a
higher resistance if you are worried about the heat and it still
functions.
Concerning rocking a car to adjust the valves. On stock MG's this is
probably be OK but be forewarned that, on some more aggressive cam
grinds, turning the motor backwards could cause damage to the cam and
lifters. You are also forcing the timing chain tensioner back and
temporarily putting slack in the timing chain. I have a mild road cam
in the A and push it backwards to adjust the valves. I doubt that I am
doing any damage. I wouldn't do this on a full race engine, however.
If the timing chain is really trashed I suppose you could jump a tooth.
Regards,
Bill Eastman- in a cautious mood
61 MGA suffering in storage while the mercury soars to 57 F today.
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