Huzzah, it would seem that the nasty noise is gone. I am keeping my fingers crossed that it stays gone. I took it to a parking lot once it was warmed up, popped the hood & revved it. The nasty rattle / buzz from the engine at 3100RPM seems to be gone. The timing chain does seem a little noise between 3200RPM and 4000RPM, but I think that that is pretty normal. Timing chains are sort of noisy.
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I replaced the timing chain tensioner piston tonight. As far as I could tell, the existing one was just fine. Maybe my memory is bad, but I seem to recall having to compress them about 15mm when installing them. These two only needed to be pushed up maybe 5mm to get the threads started on the tensioner cap. Is there any chance that someone on here can go pop their tensioner piston out, just enough to see how much of a gap there is between the start of the threads and the head (basically, how much does the tensioner get compressed when installed)? That would really help me.
If for some reason my tensioner piston is not compressing as much as it should be, then that means that there is some slack somewhere in the timing chain assembly. I was just in there, and all guides looked great (less than 60k miles on them). The chain does not stretch all that much, and it also has <60k miles on it. The ONLY thing I can think of is that I was sent the wrong idler sprocket when I replaced the dead one...and that seems SUPER unlikely.
And perhaps this is much ado about nothing. Maybe I am just a lot stronger than I used to be and it is easier for me to push the tensioner piston into place to get it threaded. I have done a lot of rock climbing over the last few years!
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Here's the other thing I did tonight...I added 1 quart of 15W-50 oil. The oil level was just below the lower line on the dipstick. The oil is also REALLY dirty and smelly for some reason. I changed it 4000 miles ago, when I overhauled the motor. I am thinking that all the excess gasket sealer has worked its way into the oil & is gunking it up. If that is the case, it sort of makes sense that I would be getting ugly timing chain noises once the motor warms up. All that crap in my oil probably degrades the viscosity a lot. When it is cold & thick, it has enough viscosity to keep the tensioner piston pressing hard on the rail.
Once the oil warms up, the viscosity breaks down thanks to the crud, and it pisses out of the tensioner too easily. The lubrication system was designed around having fluid of a certain viscosity in there, at a specific pressure. So, you can probably see my line of thought here. Adding some fresh oil might have improved the mixture just enough so that the hot-viscosity is just enough to get things working decently. Perhaps it is time for an oil change since it is really nasty after so few miles.
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Sorry about the lengthy posting & rambling. I am generally one of those "think out loud" types, and trying to explain things to others often helps me to understand them better myself. This "nasty engine noise" issue has been bugging the hell out of me, especially since I spent 40 hours overhauling the front end a few months ago. I just want a car that I am not afraid to drive!
