Ok what happened here? (Regarding hydraulic lifter)

[BenKenobi]

Sunday, I changed my oil... I usually use 10w30, no specific brand just whatever autozone has on special, preferrably high mileage stuff. The previous stuff was Valvoline MaxLife.

This time around I couldn't find exactly what I wanted (VML 10w30 out of stock, etc) so I settled for Valvoline Durablend 10w40...

So Sunday I did that, and I took my valve cover off to 1) get to a vacuum hose that was hard to get to, and 2) retorque the bolts to spec (I had replaced the gasket a couple months ago and "guesstimated" it and over did it.. Now I have a torque wrench!) ... I also swapped out my differential, but that's unrelated to this.

Monday morning I drive to my office (3 miles) and by the time I get there I get this awful rhythmic tapping noise that matches the engine rpm. Coming from the valve cover. So one of the two things I did to the engine the day before caused a problem. So Tuesday I used my van to get around (much to my wife's dismay, heh.) and figured I'd reverse what I did. Drain out the new oil and put 10w30 back in, and actually replace (instead of reuse) the valve cover gasket while retorquing the bolts properly.

Tuesday night I replaced the oil. Drove around the tapping was less obvious, but still there. Next morning I had to deliver pizzas during the day... the tapping noise got back to where it was previously. So in the parking lot outside the store I replaced the VC gasket. While the VC was off, I pushed down on each lifter to see if any of them had any play in them and lo and behold the one closest to the rear of the car on the intake side moved. A lot. Maybe 0.25" - 0.5" ... So I'm thinkin "crap i gotta replace THAT" ... I finish up the job at hand and go back to work. Take one delivery and no improvement in the tapping. Take another and by the time I got to the customer, the sound was gone.

So I have no idea what I did right. I'm not even sure I did ANYTHING right and maybe it's the "calm before the storm" and this things is gonna REALLY break on me.

My best guess is that the lifter had some air in it, and it finally bled out?

*edit* I dunno how I wound up here. This should be in the 240sx technical forum... If a mod could move it for me, I'd greatly appreciate it!*/edit*
Modified by BenKenobi at 9:19 PM 4/1/2009

[240sxFTW]

Sorry but ive got nothing. Personally id have a reputable mechanic have a look at it. But thats probably just me. I dont like to take risks like that.