OK here is the deal, 904 heads with an old set of Isky/Crane cast adjustable rockers. Pushrod Cups allow 2 threads to show on the adjuster, so I think this is correct for getting enough oil to the cups.
Running 60 pounds of oil pressure when hot and all of the pushrods look great except the exhaust rocker for #2 cylinder. Last week it was burned black and the cup was broken. This allowed it to come out and bend the intake pushrod. I replaced the adjuster ball and put in a new set of pushrods. I pulled the head and no problem with the valves, they are not hitting the pistons and nothing bent or out of line. Same valve springs pressure on all cylinders. No coil bind, not even close. I am running spacers with 60 thousands clearance instead of springs between the rockers, could this be a problem?
I was running a roller cam with over 700 lift and swapped to a smaller roller cam with 640 lift. Never had any issues with the bigger cam.
The rocker shaft had some scratches the last time this happened. I pulled the rockers off, re honed each of them, polished the rocker arm shafts again, cleaned everything up to make sure nothing was inside the shafts and reinstalled them. This week, the #2 exhaust pushrod cup is noticably smoked and both the intake and the exhaust pushrods are bent which allowed the lifters to come out of their bores. The adjustor ball still looks good and is smooth.
What am I missing? Is it just coincidence that it is the #2 cylinder each time? The only thing I have not checked is the valve guide clearance again. But I am not sure what would have changed on the heads with the cam swap that could affect the guides.