GM Repair Questions? Ask a Mechanic for Answers ASAP
Don't worry, we all make mistakes, that is what makes us human!!!
WE need to verify the exact position of the rotor in the distributor when the engine is at #1 cylinder top dead center. Turning the engine with a wrench with the #1 plug out and feeling for compression with your finger as you turn the engine with the wrench will help you find the compression stroke on the #1 cylinder rather than the Exhaust stroke.
There is a notch in the timing cover and a line on the harmonic balancer that lines up with the notch for the timing marks.
It is very likely something is installed wrong and the rotor is one, but if you lines it up properly and the rotor went into place, then I doubt it.
The harmonic balancer is the large round pulley at the bottom of the engine that the belt runs on.