Thanks for the helpful replies!!!
I took both valve covers off. Embarrassed to say I did not adjust the rocker clearance on the new head. Not sure about "caps"... It came fully assembled. The clearances were too tight (actually non-existent) - so perhaps the valves weren't fully closing for the compression and fire strokes. I've set them to roughly .005" now. Rocker clearance on the other head checks out fine. I'm waiting for my battery to charge because it had trouble turning the engine over now...
By the way - how would it be possible to mix up the intake/exhaust sequence during re-assembly? I checked and it appears the intake valve opens just after the piston reaches TDC and closes near the bottom of the stroke. Both stay closed on the way up. Then stay closed on the downward power stroke. The exhaust valve opens near the bottom of the power stroke and stays open during the upward exhaust stroke...