That's definitely "a" issue. It might be interesting to see just how far off (late, or retarded) the valve timing might be. N.b., this is different than ignition timing.
A quick & dirty method is to roll the engine over by hand slowly clockwise 2 complete revolutions and stop with the pointer on the "0" TDC mark. With the distributor cap removed, now slowly turn the engine counter-clockwise while observing the distributor rotor. As soon as the rotor starts to move, stop turning, and note how much "slop" there is measured in crankshaft degrees.