First start issue

[Vincent 911]

I bought in july 07 a 911 SC (78 ROW). I discovered 5 broken head studs and broken valve spring. I decided to do the job on my own. The engine is only 60 kmiles so I decided to not open the case. It was my first 911 engine rebuild so I decided to not take too many risks.
.I put 24 new steel studs. The valve job has been done by a machine shop. They replaced valve guides, valve seals and 1 new valve spring (#3 intake outer spring was broken).
Thanks to Wayne's book the rebuild was pretty straight forward.
I added a few upgrades: camshafts regrinded to 964 profile, Carrera tensionners, RSR rocker seals, a brand new pair of SSIs and a Dansk muffler... I tried to my best and spent many hours for this rebuilt.

I put the engine back in the car last sunday. This evening was the first start. I have followed Wayne's procedure: 10 quarts of oil, I have rotated the engine by hand and then 20 seconds with the starter to increase oil pressure.
Finally I put back the fuel pump relay and coil wire. And the started at the 2nd trial! Awesome. It ran nice and I increased the rpm to 2000 rpm for 20 minutes. I was proud of my work. It did smoked for 5 minutes and then the smoke disappear. I believe it was due to the excess of oil I put on the rings and the new muffler.

I was standing near to the car listening to the flat 6 sound and checking for oil leaks.
After more than 5 minutes a noise appears. It was like 2 metallic parts hitting each other. The noise started to increase. I immediately shut down the engine. What can it be?

So I rotated very slowly by hand the crankshaft pulley. It was OK but I can hear a little mettalic noise like a spring noise. I was not loud but still there . So I removed both right upper and lower cam covers and saw that the noise appears when the #5 intake valve is opening.

Hundred of questions are currently moving in my head:

1- What is the next step for me? Do I remove the engine? Do I remove #5 intake rocker? Can it be something else than intake valve #5?

2- Did somebody have already experienced this type of issue?

3- Why does this noise appeared after 5 minutes and not from the beginning? Did some parts came loose? Did something broke?

5- What can I did bad during the rebuild?

I will try to sleep a little bit tonight and think again tomorrow.

Thanks for all.

I believe these 911s need to have attention but sometimes it gets disappointing.

[Vincent 911]

Me and my SC.

[efhughes3]

Do a search on circlips from the last week or so. Someone had similar issue, and it turned out he had a circlip that was either forgotten or came out due to a buggered up piston. His was fine for a few minutes, and then the wrist pin would start to walk out and bang on the cylinder.

I'm not saying this is your problem, but it was so recent and similar, it came to mind. Someone had recommended he look at this as the problem, as they had experienced the same issue years ago.

Hopefully, it is something more simple. You need to get a broom, and cut off the handle and listen around your engine to determine exactly where is is coming from.

[wmunchovie]

1. Broken inner and/outer intake spring on no. 5 ?
2. Valve seat on no. 5 ?
3. Both valve retainers in place ( is one missing )?
4. Get an electronic stethoscope from harbor freight.

get led flashlight ( bright ) and mirror and inspect while someone turns crank pulley clockwise..

good luck,
munchovie.

[efhughes3]

I think most of the engine gurus here will tell you the stethoscope is useless in narrowing down the location of the sound, nothing beats the broom stick.

It may be one of the things listed above, but the fact that it doesn't kick in for a few minutes would probably go against it?

[efhughes3]

This is the thread I referred to read thru the posts describing symptoms, and then when the circlip issue is suggested.

Top-end rebuild - now I have a knock

[Vincent 911]

Thanks, I did have a look at this thread a while ago. I kept that in my triple check every pins were on the pin before puting my heads back. But nobody is perfect...

It could be a broken spring or seat.

With the help of my fellow who have an SC as well I will check while slowly rotating the crankshaft tonight. I will remove rocker #5.

[3.2 CAB]

Vincent, I hope that you find a very minor item after all of your time and effort to get things right.

Ed, why do you say that an engine stethoscope is useless? I have not used a Harbor Freight electronic type, but I do use a standard type engine stethoscope, that has the listening probe which is about 1/8" diameter. I have found that you can isolate very subtle noises with it, and can pinpoint various engine noises, you can test and hear each injector actuate, and really isolate noises better than a long screwdriver or broom handle. I have used a long screwdriver and even a very long socket wrench extension, they work, but, with the non-electronic stethoscopes I have, I have been able to locate the exact location of noises, that with the extension, or dowel rod(broom handle) just got you close to the location. I would have to change doctors if one pulled out a broom stick to listen to my chest. Just my $0.02

[3.2 CAB]

Vincent, I was looking at the picture with you behind the car, and saw the jackstands and thought holy$hit, that thing if about to fall, rolling forward!! Then I looked at the picture closer, and notice the wall studs and hangers leaning also, I could then tell that the shot was canted and not squared up. Good luck on the search!

[Vincent 911]

Originally Posted by 3.2 CAB

Vincent, I was looking at the picture with you behind the car, and saw the jackstands and thought holy$hit, that thing if about to fall, rolling forward!! Then I looked at the picture closer, and notice the wall studs and hangers leaning also, I could then tell that the shot was canted and not squared up. Good luck on the search!

Yes, the whole picture is tilted.
I did add a secondary pair of jack stands underneath my jack plates and prevent the front wheels to move.

[Eagledriver]

Maybe you just have a loose adjustment on the valve. As the engine warms up the clearances open up so they tend to make more noise. I'd check you valve adjustments and try it again.

-Andy

[Vincent 911]

Originally Posted by Eagledriver

Maybe you just have a loose adjustment on the valve. As the engine warms up the clearances open up so they tend to make more noise. I'd check you valve adjustments and try it again.

-Andy

All right. I will try that first.
But I am wondering how can the rocker / valve make a such noise if they are out of adjustement... Why only 1 rocker / valve?

Thanks

[Vincent 911]

All right, I started to remove the engine yesterday evening. If everything is OK it should be out of the car tonight.
Yesterfday I tried to look at both #5 valves with a small mirror but I didn't see anything anormal. The noise was still there when you rotate the engnie by hand. I ma pretty sure the nois is coming from intake #5.

[p930t]

Ahhh.. i feel with you ,,, I am doing the same work on my 78 3.3L . Just disassembling now due to head studs.
Will send the heads away for check.

My first time rebuilding a P flat6 so i am crossing my fingers for first start.

Keep us updated.

[911pcars]

I agree with first using noise isolation techniques (rubber hose, stethoscope, etc.). An engine noise can be caused by numerous items - too many to speculate.

It should have been fairly easy to remove the valve and chain box covers to visually inspect the pieces inside. After that, you have to go further.

A technique to isolate con. rod bearing noise is to short out that cylinder to remove the load (disconnect spark plug wire). A reduction in noise indicates a failed bearing.

Hope this helps and best wishes. Don't be discouraged. It happens sometimes.

Sherwood

[TibetanT]

Subscribing for information purposes.

Good luck with your investigation and I do hope it is something simple.

[munsonbw]

Vincent,

Here is my personal experience after doing a similar head stud rebuild. Started it up, and no noises and no problems, with just the HEs. I was doing a custom muffler, so before I got too far, I wanted to ensure the engine was good. Fabbed up the muffler, then I swear a knacking noise gradually increased in presence. To me, it sounded like a rod knocking and appeared to be coming from the head area of the motor. After reading many threads and asking advice, there were as many opinions as posts. The first thing you need to do is stop the engine drop unless it is too late. You can do far more diagnosing with the engine in the car than with it out. Use a long screw driver, broom handle, whatever and listen around the suspect area. You should hear the valves and chains and all mechanical things. If you don't hear your noise, then use some vacuum tubing or similar to listen. This is what I finally used to find that I had a really bad exhaust leak. I could not hear it with the screw driver, but the hose found it right away.

Once you have the noise isolated, then begin to narrow down the root causes. Double check you valve clearances and while you are at it do the valve clearance check in Wayne's book. All of these should be able to be done in the car. After all this is done, you should have more information to share and hopefully the group can further pinpoint.

Good luck, Ben

[Vincent 911]

Too late... I did drop the engine saturday and tear it down today. Here is what a found: nothing anormal according to my basic mechanics skills. I checked the valve clearances and it was OK.
I removed the right cam tower and #5 head. I removed intake #5 valve and I didn't found any wear mark or anormal free play.

Right I don't know what to do: reassemble and retime the engine or dig deeper?

Thanks

Some picts:

[munsonbw]

How sure that are you that the sound was metal on metal? You mentioned in the first post you could here it when the engine was turned over by hand? This does seem like pretty strong evidence that there is an issue that needs attention. While you are that deep you might as well pull the cylinder and take a look at the rings and wrist pin (one guy had a circlip get loose and the pin was banging the cylinder wall). Also, since sounds are easy to get off by a cylinder you might as well pulls the heads off of 4 and 6. I am no engine master, so you may want to wait for some others to chime in.

[h20cooled7]

I had a VW Touareg 3.2l v6 from the factory the circlip for the wrist pin was not seated and was allowing the wristpin to float and hit the cyl and crack the bottom of the skirt of the piston. I know its not a flat six but sounds like the noise you are hearing, take it for what its worth!