I'm no expert, but if not the valves you may have a small exhaust leak at the flange? Perhaps recheck your heads to make sure the nuts are properly torqued.

Silver, The motor build looked good. I don't mean to scare you but there may be a different perspective to what you are hearing. Same sort of sound happened to my 3.o over a year ago. I started to relate when you pulled out the stethoscope. One question first, does it make the noise more prevalently when driving into turns? I thought my similar noise was chain tensioner failure, too, except I was hearing it on the right rear side of the engine. Took the cover off and tensioner was fine as was the left. I'd been meaning to go with Carrera Oil Feds anyway so placed a set hoping it would solve the problem.... and for a few miles I thought that was the trick. Make a long story short the noise you are hearing can easily be a spun rod bearing on the crank. Oh yes, the engine sounds good and smooth, but only at high RPMs. You might want to consider that's what is wrong.... as catastrophic as it sounds. Sounds like that's the next and only place left to go after all your thorough investigating. Of course this means an engine pull, taking the noisier side down to the pistons and feeling and looking at .... the #5 first.... ( last to get oil).... Sounds like you watched the oil pretty well... but you'd be surprised how much oil these engines eat up even without smoking. You may have a block squirter that is blocked if you fine a spun bearing. Like I said the is just the worst case scenario..... Hope my answer is not the correct one and a much easier and less expensive one is found.

Dear Silver 911

The other option could be a weak spring on one of your valves. Did you replace the valve springs? If you used shim spacers did you forget any? Or a valve seat may have come loose which if it has not come all the way out could be rattling or ticking. You could have a mechanic check the springs force by hand only. This is difficult to time the valve so both valves are without pressure and the piston is not near the top. This takes a sensitive touch with firm hand force to move the spring. I have heard some experienced mechanics have done this. I do not recommend you perform this function but an experienced mechanic.

Good luck

Thanks for sharing your engine noise issues with us. I have a similar problem finding the source of a noise in my Euro 3.2 engine. Very interesting thread.

Good luck finding the culprit.

Henry

If you want to do a qualitative check of valve springs, make a tool like this.

http://forums.pelicanparts.com/uploa...1259630044.jpg

Here are dimensions:

http://forums.pelicanparts.com/uploa...1259630078.jpg

You use a washer, nut, and convenient valve cover stud as the fulcrum, and push down on the top of the adjuster. If there is a broken spring, inner or outer, it should feel weaker than the rest.

This tool is courtesy of Wil Ferch.

As to rod knock, I'd be inclined to have an oil analysis done before buying into that awful thought.

Walt Fricke

Intermediate summary:
1st possibility is a bad fitting between the new chains and the partially worn sprockets.
Although I like the idea (-> no work :)), do you think the sound could match to this?

2nd possibility: exhaust leak: quite common, but I have checked this before.

3rd possibility: bad valve spring. For me, the sound would match here best. So I am going to build the little tool and check. Great idea, thanks for sharing the tool description!

4th possibility: valve seat (partially) come out.
Has anyone an idea how to check this w/o disassembly of the engine?

4th possibility: rod bearing: although I hate the idea :eek:, I am getting more familiar with it.
Has anyone experience if and how to better check this?
I have pulled the spark wires one by one w/o any effect. Anything else to try?

As the temps now drop to freezing point, I will not much work on the engine the next weeks. Anyhow, further ideas are welcome and I'll keep you up to date!

jens SmileWavy

Pull the valve covers and check all the camshaft lobes/ramps for excessive wear due to oil starvation. The fact the noise improved when you adjusted the valves is pointing me in that direction. The noise pattern (not so bad at cold startup but much worse after warmup) is the same type of noise I had with my 930 engine.

http://forums.pelicanparts.com/uploa...1260023435.jpg
http://forums.pelicanparts.com/uploa...1260023499.jpg

Update
 

Hello again,

Winter is over now and I just want to share the news on the noise issue...

Some very 911 experienced guys "heard" the noise and all said that the noise is too low to be a piston or rod bearing issue. Must be something with rockers or valve spring.

The last days, a friend of mine and myself disassembled nearly the whole valve train (with engine in the car). We removed all rockers and shafts, inspected them for wear or anything strange. We inspected all valve springs using an endoscope and even removed some which were suspicious at the first look.
We also checked all head studs etc., searched for "loose objects" etc.
Nothing detected :confused:

After assembly, valve adjustment (only minor corrections), and sealing up, the car runs like a champ...but the noise is still there :eek:

So I will keep driving it, unless the noise gets stronger-or anyone has other ideas.
Maybe it is something totally different, like a loose piece inside the heat exchangers???

Thanks for all your contributions. If any time in the future I'll find the weird thing, I'll let you know.

Jens

http://forums.pelicanparts.com/uploa...1271414130.jpg

those aren't that bad... these are:

http://forums.pelicanparts.com/uploa...1271417965.jpg
http://forums.pelicanparts.com/uploa...1271417980.jpg
http://forums.pelicanparts.com/uploa...1271417998.jpg

thanks MM for crappy work.

you have an oil squirter plugged in your cam tower...