one lifter bleeds down. Any thoughts

Just finished rebuilding my 360 for the Cuda and got it in and broke it in with just the outer springs and 15W40 Rotella with the GM EOS additive like Comp cams says. Then changed the oil and ran it long enough to get the timing set right on 34 total and adjusted the carb. Took a little spin over to the next wtown and filled it up with premium and came back home. Started it later for a buddy to show him how it sounded. Never made a lifter tick at all any time. The next morn. after it cooled off I pulled the valve covers and installed the inner springs and reset the rocker arms (got Comp cams stainless adj. roller rockers). Fired it up and had a lifter hammer for about 2 seconds. Didn't think nothing much about it. Now allmost everytime I start it that lifter hammers bad unless I rev up the engine to like 3500 or higher. Then it will go away. Oil pressure is real good at 30psi at idle hot and 60psi down the hwy. BTW this is a new cam and lifters, the Comp XE 274. I put about 90 miles on it and changed the oil again. Found no metal in the oil (thank God). Still does it. I pulled the valve cover and Its the exh lifter on #7 and I can easily push it down with one finger. Like it just don't hold any pressure. Anybody got any idea to fix this pig other than pulling it all apart?

Sorry for the novel.