Chain noise when warmed up???

[clif]

I have a 74 911T with about 50K on rebuild. It has sat a fair amount the last couple of months. When I warmed it up the other day it sounded like I had a loose muffler and sound only happens at idle to 2600 rpm at which point it quits completely. Not really a sound I would describe as a chain on a garbage can, again more like a loose muffler. I went to check it out and have discovered this sound only occurs once engine is warmed up (gets progressively louder to a certain point). From what I have read bad tensioners sound is worse at cold start. It appears to be from chain tensioner cover area but using a stethoscope I can hear noise resonate back thru intake. Can these tensioners react this way when first going bad? Or should I be looking somewhere else. By the way, exhaust is fine, no leaks or loose areas. Sound is louder under left chain cover than right, but I can hear on both sides using stethoscope.
thanks

[dean]

You don't say what kind of tensioners you have. If it were me and I heard a chain noise I would pop the covers and have a look. And hyd. tensioners can act that way

[clif]

This car has low miles, but the engine work was done over twenty years ago. I am sure they are the stock type tensionsers for the 74 (old hydraulic type)

[grant lyon]

Don't know if your 74 has an air pump, but the smog air check valve on my 76 gave me a scare with clattering noise. Close to chain cover. Easy to check with the stethoscope.

[clif]

Ok thznks, will check

[power]

I'd continue to look around the exhaust cylinders ect....for source....if nothing, I'd remove the chain covers and take a look, make sure your familiar with all aspects of how the chain, tensioners and ramps work together. The most this will cost if not the source of the noise, is new oil and new chain cover gaskets....

[cstreit]

How exactly can you tell if a tensioner is failed by just looking at it?

[power]

The two I have seen were quite obvious upon inpection (possibly due to the fact that they were both mechanical). One was not maintaining tension on chain (slack chain). The other had worn a groove where it was rubbing the housing when the chain went slack. This one had started to chew into a chain ramp as well.
hope this helps......