Lifter preload...more or less?

I like .040 for Comp lifters. I have set the as loose as .010 with no increase in performance. They were noisy at idle with .010 preload and 5w-30 oil. Tightening up to .040 preload lessened the noise tremendously. Running 10w-40 made it go away completely.

I agree with others on calling Smith Bros.