rakka rakka rakka
1st, kudos to you for coining that phrase to describe the sound... that is exactly it!
Anyway, I unfortunately do not know if I've got a variable cam gear. I don't think so. But the sound seems as if it is a result of the chain tensioner losing pressure. The funny part is that it happens very intermittently. Sometimes happens hot. Sometimes cold. Sometimes never. Bizarre.
I'm prob a bit at fault here. As much as I HATE to admit this and you all will prob send a lynch mob after me, I run regular 10/40 and have changes done at (gasp!) Firestone (I watch them like a hawk, but they're VERY reasonable and have provided great service for oil changes... hey, I do 22k / yr!). I mention this as maybe the filter they get from Napa, etc., does not possess the correct attributes (the check valve is in the HOUSING, not the filter though, right?)??? I used to run diesel oil in my ///M5, 15/50HD I believe, maybe I'd benefit from this as well?
Any thoughts (besides not going to Firestone for oil changes!!!). Thanks.