Engine whrrr noise at 1500 rpm

[opata]

Hello, trying to figure out if all is well with my 80 sc 3.0. Their is an engine whrrr noise that appears to come from the timing chains at around 1500 rpm. Is this normal? and sometimes on deceleration...otherwise it runs great! I rebuilt my engine and it has 3.5k on it sense the rebuild. I also installed pressure fed tensioners. I do plan on taking the covers off to check the tension on the chains.....
thanks!!!
Alan

[hcoles]

my 2 cents

might try other window analysis before removing chain covers e.g. remove fan belt and take a very short run if can't duplicate with car stopped, I assume the other belts are off

let an expert confirm the idea to remove belt with a short run before trying
can you get others to listen to see if they have heard the same noise?

[Patronus]

I assume you used new chains and guides and also spaced the chain sprockets, with shims, to within the factory specifications. It is unlikely but not impossible for a pressure fed tensioner to collapse. What you describe may be a tensioner but here are a few questions first:

Has this noise been there all along or has it recently started?

Is it worse when cold / hot?

Can you hear it coming from the one side (left/right) more clearly than from the other?

If you put a long screwdriver against the chain box and press your ear against the handle (make-shift stethoscope) what do you hear? Try listening to the tappet covers also to make sure the noise comes from the rear of the engine.

You can perhaps disconnect the fanbelt for a number of seconds to eliminate possible noises from the alternator, if you're still unsure about the source.

[opata]

Ok, thanks for the replies! I think the sound has always been there. Up until this point I though It was normal. This is my first 911. Yes, I replaced everything with new parts. The shims were already their so I just put them back b/f I placed the tensioners on. They were like a 1/4" washer right? I think the noise is coming from the center but will take a screw driver and listen after work today. The noise is not present at idle and seems fine when I accelerate.... doesn't make a difference if it is hot or cold. I'll also try to take the fan belt off. Again, I really don't know what a normal 911 engine should sound like. I've listened to threads on youtube and I have recorded my engine running on my phone but can not hear the sound?? Anyway, I might be making something out of nothing?
Thanks!

[Flieger]

Failing tensioners usually rattle "like marbles in a coffee". Whirring is usually alternator (fan) bearings. There is a normal whirr associated with the spinning fan and properly operating chains, even with good alternator bearings and good tensioners. It sounds a little turbine like. When things go wrong the tone gets rougher.

[opata]

Ok, thanks! I really appreciate the help. Again I could be chasing a ghost but better safe than sorry. I'm going to do more checking after work...
thanks!

[Patronus]

If the sound comes from the middle of the engine it isn't a tensioner because with a tensioner the noise will be on the one side or the other. Also, if a tensioner collapsed you feel the pain when you hear the sound. You can tell the engine is hurting.

The culprit may be an alternator bearing or even the fan (check for a damaged blade). Easy to check with the fanbelt disconnected.

Maybe your car is OK but you're not used to the sound, as you say. I once had a guy complaining about his engine after we fitted a stock exhaust. All it was, was him hearing the natural 911 engine sounds (and not just the exhaust) for the first time.

[opata]

Hello, Thanks! At this point I think the engine is fine. I'm just jittery b/c I rebuilt it and in the back of my mind I'm thinking I didn't tighten a nut somewhere I will disconnect the belt when I get a chance....
Thanks again!

[hcoles]

I have a hollow whirring type noise, I hope alt. bearings and not something worse. My top end is rebuilt and I only have just over 100k miles. I'm just going to keep an ear on it, can only hear it with deck lid open. I should try my own test of belt off but this is not getting to the top of my weekend do list yet.

[opata]

I think the noise sounds like the chain rubbing across the chain guides?? is that normal...again I have new pressure fed tensioners....I still plan on opening the covers to look....
Thanks!