4.6 question

Ok, I'm asking this question here because most all of you guys are more knowledgeable than a lot of the people that populate the other forums. So please don't flame me for this.

In addition to my big block mustang, I have a 96 gt. 4.6 with worked pi heads and bullet race cams from modular head shop. Bottom end is factory. Was tuned by modular depot when the were in Florence ky. Car runs like a raped ape. Has oodles of power. Put down right at 300 to the wheels on the dyno.

It's developed a nice tick/tapping sound. Which initially was thought to be lash adjusters (could still be, idk). Checked lash adjusters on passenger side as well as timing chain tensioner and everything checks out. Haven't done the driver side yet so I can't rule that out completely. Thing is I can't pinpoint it with the stethoscope. It seems like it's is more prominent when the rpm's come down instead of revving or accelerating up and completely goes away at idle when it's warm.

I had actually started leaning towards a rod bearing but I would think that the rod knock would be there all the time including idle and would be more of a banging than a tapping, correct? Is it possible that it could be a lash adjuster pumping up when pressure goes up when revved and bleeding off when the pressure drops? I'm thoroughly confused by this one boys. Anybody have any ideas?

Thanks
Jeremy

What oil are you using...?

The gentleman I bought the car from was using Mobil 1 5w30 so I followed suit. I'm pretty sure it calls for 5w20. Oil to thick to properly lube bearings?