Ok, so I'm out today to battle this "rattle" at 1500 to 2100 RPM. Car has 60K on it...excellent oil change history and everything looks whistle clean under the cam cover and down in the chain case. I put a new upper chain tensioner on it (still rattles) and today I decided to put a new upper guide on. Upon inspection it is clear the side opposite the upper tensioner has a bunch of slack in it that no amount of tensioning on the tensioners side will remove. The upper guide when removed looked new but I replaced it with the new one anyway (heck I bought it mine as well use it!) My question is does one loosen and move the cam gears to move the slack to the "tensioners" side or is this best left alone. I'm beyond frustrated at this point and don't want to do something drastic that will jeopardies the cars engine. It's beyond me as to why there is so much slack in the drivers side of the chain...I could relate if the car had high miles or was abused but that is not the case.

 

OK, what I found with mine.

That small "top guide" in between the 2 camshafts is basically a "whip eliminator", and I have never seen one with much wear at all, as the chain length there is minimal. Even our ancient AJ6, and 360k kms had little to no marks on it when I stripped the engine due to it dying.

My AJ16 had the same as yours when I simply fitted the top tensioner unit with another "update" unit. Better, yes, right, no.

I eventually stripped the timing cover and found all sorts of ills, not too happy, but what can you do, replaced all the guides/dampers. and chains whilst in there. The old chains were just fine, and only coz I had them did I replace them.

My lower tensioner was sad to be polite, so the piston assembly from the "old" top tensioner was used in that housing. Pre firing that particular unit is testy at best, and unless you pre fire it, it will NEVER fire. I got it wrong the first time, and that damn rattle persisted, so off a second time, and the "unfired" unit was clearly visible.

I always "per fire" that top unit as someone else also said on your previous post, I NEVER let the engine do it, it is a silly suggestion in MY opinion.

My car also had impeccable Jaguar service history, and although not squeaky clean in the camcover area, the timing cover was squeaky clean.

The "slack" you mention on the LH side sounds like the top unit is simply not applying tension to the RH side. I wound my engine (by hand) to take up that slack prior to firing that top unit, but I reckon it would sort itself rather quickly once running, as long as that unit is fired off.

I would not mess with the camshafts for that between chain slack, simply rotate the engine by hand, just a small amount, and the slack should take up, and locate itself on the RH side where the top unit "should" take care of it.