Truck came in for heads and this happened.....

Um.. Are the pushrods in the lifter seat?

Are the pushrods too long?

Lifter pumped up, and wont self regulate. Basically causing valve float. Have a 6.4 in the shop now. Same problem.

Have you looked at the rocker arms? I know typically they wear down which, in theory allow more clearance, but could they be bent, or not seated on the pivot ball correctly? Or possibly the valve bridges not seated correctly? Also do you have the new heads checked i.e flatness, valve height etc? I've had some pretty sorry heads come from ford before. Just food for thought.

Did you ever figure this out? Just finished installing an "enhanced" short block from Ford, reman heads from ford (long block wasn't availible) and now I have the same problem, cylinder 5 exhaust valves hanging open. Pushrod is installed correctly. Backed off the rocker bridge bolts on cylinder 5 and I could see the valves close. Going to check valve height tomorrow but looks like a lifter or cam issue.

Figured it out, old pushrods are longer than the new ones ..