Chasing strange sound in 964 engine

[Kroggers]

My new to me 964 3.6 transplant engine has a strange tweeting sound - closest way to explain it, sounds like a small bird stuck inside

I did drop-in to my local Porsche specialist that did a quick (free) investigation with an electric engine stethoscope. He concluded that the sound was coming from the lower right hand side at the front of the engine. He sugested to first check behind the power steering block-off plate, and if all was OK there to remove the bottom right hand valve cover.

The sound as I said sounds like a tweeting - as if there is metal to metal rubbing. it is linked to engine speed, so gets faster as the engine speed increases, but the pitch of the sound will not change. Also, whilst the sound is there most of the time, I have had it disappear and then fade back in again a couple of times. It is also rather laud, can be easily heard above the sound of my 2in 2out M&K muffler...

I had a look behind the power steering block-off last night, and have concluded that all is good there. So the next step is to remove the valve cover to have a look. But here is my problem - I have no idea what I should look at and how to check if things are good or bad

So if anyone could give an ideot like me some guidance on what to look for behind the valve cover that might make a tweeting sound on a running engine and how to verify if it is good or bad, then It would be very nice

[Don Settergren]

Maybe some more information on your engine might help. The engine is new to you, but what happened before you got it? Was the top-end rebuilt? Any new seals or gaskets? Any new parts?

As for the sound itself you say it is engine speed related. Does it tweet once per revolution, more or less?

I would first check to see if there is anything rubbing against the engine or transmission. Run you hand and visually inspect the entire surface of the drivetrain looking for something hanging down and touching the engine. Wouldn't it be nice if there was a lose screw grinding against the engine every revolution as the engine slighly moves around...

[JFairman]

From your description it could be one or more clogged cam spraybar holes.
If that happened then the cam lobe and rocker arm would be running dry and could make a course squeak or bird tweet like noise that would get worse if you kept driving the car like that. I don't know if you have any of the 964 power steering pump linkage or hardware in there still.

After a short while metal would be worn and scored away and valve clearance would increase rapidly and you would hear the rocker arm tapping against the cam lobe more and more if you keet running it.

You can take the upper valve cover off without draining the oil and look at the cam lobes for scoring with a flashlight or whatever, a small mirror may help see in there, and you will have a big oil mess on the ground if you remove the lower valve cover without draining the oil first.

[Kroggers]

Now I am really confused. I decided that I would put the power steering block off back on and start the engine so that I could take a video and share with you all the sound.

I also decided to quickly check that the lower spark plugs on that side were in nice and tight, and they all moved about a 1/4 turn more.

But the sound is all but gone!?!

I took the car out for a 45 min drive with some fast motorway as well, and apart from a slight ticking from the valves, there is nothing else!

I am not confident that the sound will not return, but for now I am just going to drive and enjoy

[WERK I]

Originally Posted by Kroggers

I also decided to quickly check that the lower spark plugs on that side were in nice and tight, and they all moved about a 1/4 turn more.

But the sound is all but gone!?!

I took the car out for a 45 min drive with some fast motorway as well, and apart from a slight ticking from the valves, there is nothing else!

That will certainly do it! Was that a quarter turn to the proper torque? I would still take off the valve covers and inspect the lobes.

[Kroggers]

Originally Posted by WERK I

That will certainly do it! Was that a quarter turn to the proper torque? I would still take off the valve covers and inspect the lobes.

I will have to confess and say no, I find it impossible to get my torque wrench under there to check, so I use a small socket set with a spark plug socket to check them.

It is soon winter over here, and we are moving from Sweden to Finland at the end of the year. I have found storage for the 911 in Finland, but need to get the car over before the snow and salt starts. So I will be driving her over on Tuesday.

I will schedule to check the valves etc as a first priority when I take her out from storage again next summer...