They followed the instructions, just not all the way through. They must have needed them for a kneeling pad. They made it to the first fitting and made sure both boilers were the same. "Connect riser to boiler with 2-1/2" elbow and nipple (not shown)". That part is to the letter on both boilers.
Now onto the puzzle. In calculating the venting, I figured the short main (16' of 2" feeding 2 rads) would need 2 Gorton 1's. The long main came out to 1.8cuft. so I used a B&J Big Mouth on that one. On a start up with timing starting when the 4" riser is steam hot, it took 6min for steam to close the Gorton side. After 6min 30sec. The Big Mouth stopped venting. When you take the vent off, still nothing. The boiler continued to fire for the next 12min. At 18min., the B&J vent started venting again. 2min. after that, steam arrived along with the sound of the water draining and some minor water hammer until the vent closed. Roughly 25' of the piping in inside an oak soffit. When I look through from either end, I don't see where the dry return could have any kind of a sag that would allow enough water to collect and block the system from venting. On a start up cycle the auto feeder cycles 2 times on the warm up. On long off cycles the water level in the sight glass is about an inch from the top. Would it be worth while to check the fittings at the end of the main where it drops to the dry return to see if there is something restricting the flow and allowing water to stack. Or can I assume the whole problem stems from the improper near boiler piping? BTW I did put in a skim port and skimmed the boiler. I also removed the bottom plug and wand washed the boiler.