Wow, valve springs? Musta been pretty tired!
Did you check the loads at installed height of the old tired ones to find the culprits?
No, I just pressed on the rockers with my hand. The first 1/8 inch of spring travel was like a wet noodle..One guy out of dozens who responded to the engine problem on several websites got it right. He said in fleet service the springs would fade away an allow lifter pump up at idle.
