Noisy valves again after engine rebuild....

dick911 · 10-10-2005, 01:17 AM

Hi, I'm new here. Great forum !

I'm sorry in advance for my english/american, I don't know all the right words.

I bought the Engine rebuild book before I send my engine (3.0 SC 204 hp) to a independent Porsche specialist here in Holland.
There is really good advice in it.

The engine just covered 182.000 km (appr. 110.000 miles) when one head stud snapped. While I found that the valvetrain was also becomming noisier and noisier (not due to to much valve clearance..) by the time, this was a good moment for a rebuild.

I told the engine builder about my noisy valvetrain (rockers, "elephant feets" and rocker shafts). He inspected all of the mentioned parts before reassembling the engine. All was fine within the tollerances... Also all the needed heads-valves things were done.

Problem:
After the rebuild my engine still has a noisy valvetrain. Clearances are set to a really tight 0.10 mm. The "rocker ticking" (as I call it...) occurs aprr. 5 minutes after starting the engine.
I removed the covers to check valve clearance again and found that the clearance is good with a cold engine, but some of the rocker has a bit of left-right movement on the rocker shaft.

When pushing them by hand it makes the same sound as I can hear when the engine is running.
Strange thing is that the rockers do not have any clearance on the shaft itself as you look at it from the "bearing" side (how you call it: axial or radial clearance??).

When pulling away in alle gears the rocker ticking is loudly present; My car makes the sound of a VW Beetle....

- Anyone a guess what causes this?
- Will the noise disappear when I change all of the rockers, shafts and "elephant feets"?

Hope to hear some advice on this problem.

Best regards,

Dick

davidppp · 10-10-2005, 01:28 AM

This may not be what you'd like to hear..

My bet is the noise in not from the valve train at all.

Did your mechanic strip the engine completely?

Did he actually remove the pistons to rering ( hard but not impossible to do them in situ).

Could it be a small end?

Or a big one?

Take it back to him and ask..

Kind regards..
David

dick911 · 10-10-2005, 01:37 AM

Hello David,

Thanks for your reaction.
Yes, all has been seperated, new bearing shells in the big end etc. etc.

When I use a stethoscope (the hearing aid a doctor uses) I can hear clearly the ticking is in the valve area.

Any suggestions here?

Kind regards,

Dick

davidppp · 10-10-2005, 01:53 AM

hello Dick.

Is the tick once per engine revolution, or per two revs?

Sometimes its worth taking out the plugas and spinning on the starter motor, or even by hand using a wheelbrace on the fan nut..

(Obviously, the cam revs are half engine revs..)

Does the niose alter as the engine gets hotter?

Kind regards
David

dick911 · 10-10-2005, 02:08 AM

Hi Dave,

I'm think it's per two revs (hmmm, quite sure about it..).
Is your advice on taking out the plugs and spinning by starter motor
a method for clearing any small end clearance? Or...?

No, the noise doesn't alter when the engine becomes warmer/hotter...

Kind regards,

Dick

davidppp · 10-10-2005, 04:14 AM

Hello Dick.

Well, first if the engine is running the overall noise level makes is hard to locate the noise accuartely..

It could be from anywhere in the valve and cam set up..copuld it be from the chain wheel?

Kind regards
David

dick911 · 10-10-2005, 04:26 AM

OK, David,

It's clear to me that I have to do further investigation to the exact location.
Soon as I know more I will let you know.

Thanks for so far!

Regards,

Dick

KobaltBlau · 10:36 AM

Dick, first of all your english is better than most native english speakers on internet forums

Do indeed use your stethoscope to determine to the best of your ability EXACTLY where the noise is coming from.

I just had this problem, and I located the noise at the #1 intake valve area.

When I took the #1 intake rocker out, I could tell with a mirror that I had a broken outer valve spring. However, I would not have wanted to go taking rockers out all over without determining exactly where the noise was coming from, first. If your engine is '79-81 I would look carefully at this if you haven't replaced the valve springs in the rebuild:

Quote:

Originally posted by Steve@Rennsport
Walt @ CE, Jerry, and Bruce are all correct; Porsche installed a batch of defective outer valve springs in the 79-81 model years and this has been well known problem for many many years now.

I started seeing those in 1980,...

I tell anyone with an SC of that vintage to press on each valve with your thumb at valve adjustment time. If you can push the assembly down manually, the outer spring is broken and requires replacement. This can be done with the engine in the car,.....

You'll hear a ticking (much like a loose valve) when a spring has failed and its VERY important to fix this right away.

Henry Schmidt · Henry Schmidt's Garage

If your problem is truly valve related my questions would be:

New valve guides? reamed or honed?
New valves?
If you used the old valves, what was the taper on the stems?

With 180,000+ miles the valve stems would most certainly be
worn. They can easily be tapered .004. .0015 is too much.
With white grease for installation old valves in a new guide can feel snug.

Also if the guides were cut with a reamer an old reamer can cut the guide too large.
I'm hope I am mistaken but they questions should be asked.

Good luck.

Eagledriver · 10-10-2005, 07:52 PM

Have you listened to other 911s? A certain amount of valve noise is common in these engines. Yes if everything is replaced or remachined perfectly there will be very little noise but many times not everything is perfect and you get some noise. If it really bothers you then you can try to fix it. If there is nothing major wrong (like a broken valve spring) then you might just want to learn to live with it.

-Andy

dick911 · 10-10-2005, 11:54 PM

Hi to all,

Thank you for your reactions!

First I will answer some of your questions:
Yes, new valve guides were installed and the valve stems were all within the tolerance and not worn (after aprr. 110.000 miles = 182.000 km)

Yes, long before the rebuild I've had two broken outer valve springs.
(guess what: I replaced them with the engine in the car; I made a special tool for this action which worked well !)
During the rebuild the valve springs were all checked on height and stifness (or spring power ?) but none of them needed replacing.

I'm sure none of the springs has broken after the rebuild cause I have already revved the engine to 5000 rpm. If there was a broken spring I certainly must hear him knocking against the piston dome.... (or worse..).

Yesterday evening again I removed the intake valve covers.
I noticed that one of the "elephant feet" (adjustment screw) had more clearance then the day before... I set this one to the correct clearance again and found out that the adjustment screw thread (or spindle ?) is not in a good shape. Also I noticed that the "elephant feet" really has a lot of play on the screw.

Does anyone also experienced loose hanging elephant feet at the adjustment screws?

I just ordered two adjustment screws with elephant feet (one spare...). I will take out the rocker and replace the screw.
I hope that this will solve the noisy valve...

Regards,

Dick

dick911 · 10-11-2005, 01:23 AM

Hello again,

Update: I just used the "Search" functionality on this Forum.

Great, I found a lot of topics about "elephant feet" or "swivels"...
Man, I must say there are a lot of Porkers who experienced worn out "elephant feet" !

It's intresting, or better amazing, to read the several stories.
All experienced the same noises and all other common problems.
This will help a lot to cure the problems. I will check all the "elephants" and replace the worn out ones.

Sure, I will update you on the results.

Thanks,

Dick

Henry Schmidt · Henry Schmidt's Garage

At Supertec we replace all valve adjusters, disassemble and polish shafts and rebuild all the rockers.

I guess that why we don't experience this particular symptom on rebuilt engines.

PS: plating the shaft hardware seems to make the shafts tighten more effectively.

philippeF · 10-12-2005, 05:11 AM

Hi M. Schmidt
it seems there is a bit too much noise on my euro carrera engine too, valves are adjusted. What about a "valve guide wear" noise ?....
regards
Philippe

Mark McClure · 10-12-2005, 04:14 PM

Henry,

What do you plate the rocker shaft with? how thick? Does this improve longevity or just sealing?

SOOOOOO many questions!

Cheers

Mark......

KobaltBlau · 10-12-2005, 04:58 PM

As I read it they polish the shaft and plate the shaft hardware, but don't plate the shaft.

Mark McClure · 10-12-2005, 05:01 PM

OK that cleare things up......not too sure how plating the hardware would assits sealing but Henry obviously know this works!

KobaltBlau · 10-12-2005, 05:06 PM

My guess is the plating decreases friction between the cone part of the adjusting hardware and the "cup" part of the rocker shaft, making them tighten more smoothly.

rotorhead · 10-13-2005, 03:49 AM

Awesome thread...

I didn't realise that the rockers shafts were so touchy in the 911, too much wear then noise, too little torque then sideways movement, too much wear then leaks..... good info guys

jbrinkley · 10-13-2005, 04:59 AM

I've wanted to replace the whole shebang for a while, new it adds up to just over $1k at pp, feet screws bolts shafts arms seals. I wouldn't mind finding a place that would sell the whole works for decent $.
anyone know where to get reconditioned rockers? or is it worth it to get brand new arms and shafts together? I've had the walking shaft problems, and or leaks on more than two of mine. It's annoying and stressful.