Bent pushrod is probably a sticky valve. Why the valve got sticky, is the question. With the head off and the valves looked at you have done what you should to find out the "why". One thing to consider, old or bad gas in the tank, lines,Carb, and filters. It only takes a bit to get a valve stem sticky. Now is a good time to check. Not hard to do(smell is one way) and with the head off you have the time to check. About that head gasket: (My 235(55-60) had run many times while I took rust off the fenders and repaired the floor. I had changed the oil, tuned it up, and attended to some oil leaks. There was just so much grinding of welds and sanding of rust I could stand to do before I had to hear the engine run one more time.) It let go without notice. No running issues, no starting issues, just a big rise in the oil level. Yep oil went up on the dipstick. At the same time coolant went down in the radiator. Bad day for sure. So off came the head, and the oil pan and it was time to look at things. First I noticed the head had been resurfaced. Gasket was gone between #3 and #4. No other signs that were visible. Head was checked for straight, and cracks. It was good. Block was checked for any warpage, it was good as well. So the "why" was bugging me. The bottom end was good, clean and the bearings were good. So the "why" was killing me. Until I prepped the block for reassembly. I spin the head bolts into place before I put on the head. It is something I learned the hard way. If the bolt takes 40 foot pounds of torque to screw into the block. Then you have no idea what the true torque on the bolt is. And, no idea what kind of clamping pressure is on the head gasket. Some time with a tap and the block threads cleaned up nicely. Some time with a wire wheel and the bolts did as well. So the "why" was improper torque on the head bolts. Sort of a reality check on the "it was just rebuilt" story. Old fuel and crud on the head bolts. Not sexy but effective. Has run well ever since.
