[Hal Copple]

for one or more decades, Holley's have a built in back fire protector in the base, so it makes it unlikely but not impossible to blow out the power valve. It is a small "ball" that seals under back pressure.

The MSD fires multiple sparks under 3000 rpm, but i run an MSD, and it times just like any other car. I wonder if you are getting some sort of misread from an adjacent plug wire or something. Why don't you be absolutely sure you have no cross firing, perhaps you can clean out your distributor cap or something.

My timing light works just fine and normally off the number one plug wire. It is the front one, on the passenger side of the motor, that is number one cylinder.