Tensioner question

[ARCSinAK]

Hi Gentleman-
Any thoughts on my situation would be great.
The Engine History: 120K
Top end rebuild 4 K back, Rebuit valves, rings, all seals.
After about a thousand miles noticed a knocking/tapping noise, which seems to match the revs but is less dramatic the higher the revs. I listened with all of the usually diagnostic tools, hardwood Dowel, Metal Bar ect.
Sounds deep, worse at 950 Idle than a 1100 idle. Hard to tell where it's coming from. I have listened to all the available spots, under the case on the timing chain covers ect. My original thought was that the PO may have re-used the rod bolts and the new top end created more compression and thus leading to a possible rod bearing failure. However, the sounds has remained unchanged after another 3K of spirited driving. The engine runs strong and pulls to 6K. The general opinion I have gathered is that if was a rod bearing it would get dramatically worse in a hurry.

Yesterday, I decided to change the oil and has a look at the magnetic sump and tank plugs. Took a drive got up to 180 degrees, drained the oil, inspected the plugs for pieces of metal and metallic residue. Found no shrapnel and minimal residue.

Here where things get interesting, I added ten quarts of 20/50 and started the engine. The flat six was chattering like mad, scarred me, I thought it was done. Shut her down added another quart and started again, the chattering, gradually, over the course of a minute or so backed off to the sound that has been frustrating me. The same underlining old sowing machine style knock that I have been so frustrated by.

Has anyone else experienced a radical chattering sound after a oil change which then subsides? This 80 SC has had the hydraulic tensioner update. Could a tensioner be loosing part of its tension thus creating the noise and then have lost all or most of its tension after the oil was drained? Only to have re-tensioned itself to a partial state again? Strange how after the oil change the sound was so radical and then returned to the same some what tolerable noise.

I would much appreciate your feedback. I plan to order gaskets for the covers and inspect in the near future but it would be nice to have some opinions first.

Thanks and have a fun weekend.

[Flat6pac]

Carrera tensioners aren't fail safe, you'll have to drop the muffler, lower the engine to remove the rear sheet metal so you can get to the chain box.
Bruce

[ARCSinAK]

Thanks Bruce
I plan to go that route next, but have you ever experience a radical change in engine noises from a oil change? Then to have the sound return to it's previous state?

[Flat6pac]

No I don't recall that happening but I have witnessed several defective tensioners over the Carrera years but I've never seen one cause timing to jump like the early style tensioners.
Bruce

[ARCSinAK]

It was very dramatic and seemed odd that would return to the previuos sound after a minute or so.
Like the tensioner maybe lost tension then regained some back to where it was. If it was even a tensioner? What other parts/systems could be effected by the recirculation of new oil? I checked the oil pressure immediately and it was solid?????