not head slapping?
 

I read poeple saying you have a head stud broken and the sound you hear is "the head slapping the cylinder".

I am by no means an expert, but I found one nut on the exhuast side of cylinder #1 loose in the head. I head the noise and was crying the blues! I feared it was actually a pulled stud when I screwed the nut COMPLETELY one to the point the 10mm hex drive wont fit and am unable to torque the nut down.

I fired her up and for the life of me couldnt get that noise! 2 days later I can hear the noise.

I wonder if the nut has worked its way loose and is vibrating in there again? I have half a mind to remove the nut and close the sucker back up to see what happens!

I just want to point out that in my schoolings I have learned a precious few things including an very general understanding of the amount of force required to deflect the corner of the head made of very thick cast aluminum. It is a pretty large amount to say the least!

I have also heard of people doing a rebuild, with no broken studs on there motor, seeing a similar damage to what is claimed as this "slapping" mechanism of failure.

Where did this idea of "slapping"come from and how is it really justified?

Please dont take this as a challange to your p-car wisdoms, as I have learned many valuable things from this board in peticular, but I just want to know how we know this!

PS if you really hate my posting, I will back it with my hotmail email address, as a sign of good will: polymergod@hotmail....please be gentle!

Sin 1: having a pulled head stud
Sin 2: screwing down the head bolt until the hex bit won't fit anymore.
Sin 3: continue driving with a pulled head stud
Sin 4: Challenging the combined Head Stud expertise of the board
Sin 5: Claiming that your schooling was beter than real life experience

You're really asking for a good spanking on this one. I'll back off and let the experts speak up.

1. Stop driving it.
2. Remove the engine.
3. Get your check book out.

Check out this thread :
http://forums.pelicanparts.com/porsche-911-technical-forum/149710-head-stud-brocken-now-what.html

Dan

oh great! a few smart aXX comments!! how about some logical explainations instead?

The theory makes sense, I just want to know if anyone has had any real life experiences proving this "slapping" theory. Say perhaps seeing the damage on the heads in the specific area of a broken stud, maybe a picture or two, etc.

All I really want to know is how everyone seems to know the head is actually deflecting enough to make a noise.

What I am not asking for is know-it-all answers from people who are too close minded to hear out an idea, especially when thier knowledge is not based on theory or first hand experiences.

P.S. I have only had the car for approximately 6 months, so I hope you can understand why why I am seeking help. I have the main books published by B.A. and Wayne. While I am no means an expert, I will say that I have recently tried some DIY things outlined in these books, and found a few points that I simply think are not the best way of doing things. That is why I have turned to these messageboards, for quality info based on real life experiences.

The mating surface of the head to the cylinder does not have enough force applied between the two, as a result of cylinder preasures, the lip of the cylinder will dig into the sealing surface of the head. The longer this is allowed to happen, the alluminum will be displaced more and more(making the sound louder). Drop a nice piece of billet alluminum on the ground an look at the damage that is caused. do it a thousand times and you will get the picture.


Yelcab1 is probably right on this(pulled head stud) as is the rest of his comments. My guess is that you have a mag case since you havn,t told us the year and engine. Eveyone here may not have answered the question the way you wanted, but they are trying to help. So let them.
Start by giving the particulars of your car......woops, read your I.D.

Go to this website and buy the book. You will be glad you spent the money, I promise. http://www.101projects.com/911-Rebuild/index.htm
It describes and shows pictures of the damage done to a cylinder head from a broken head stud after only about 75 miles IIRC.
Another option is to go to the engine rebuilding forum and ask the question, lots of gear heads there. The answer will not change, but you can try.

The studs on these engines are designed to stretch to accomodate the aluminum cylinders and to keep from pulling the threads out of the aluminum or magnesium crankcase. I've never done any analytical testing on one so I can't quote the actual specs, but I'd venture that with that much pressure distributed over three studs instead of 4 there would be no way to get a seal, IF.... it werent for the cam housings adding to the overal structural support. the cam housings are one solid piece, not three seperate pieces per side like the heads. That is also why a broken stud in the middle cylinder is not as drammatic as one on the outside end (front or back).
It is real, it does happen, it does do damage. How much and how fast seems to vary between engines.

You might want to read this:

http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-1.htm

-Wayne

1980 911 SC. I have the same year and I would do this: Stop driving. Get the car up, hoist is easiest, drain a bit of oil out of the engine sump. Take the valve covers off, both intake and exhaust. Get the proper tools: Long 10mm? Allen socket for the head barrel nuts, 3/8 drive Torque wrench. You can make up a long Allen by cutting off the 90deg bend and fit it on to a 6-point socket. Carefully torque/test all head bolts to about 24 ft.lb according to the Bentley manual. A compression check would give you some indication and a base line for referrence. Hopefully, there is just a loose nut and re-torqueing all of them will solve your problem.SmileWavy Take Wayne's advise to prevent more serious damage.:)

thx for the input.

it is a stock 80 SC Euro. with the 3.0. Eng type 930/09. engine serial # 6303761.

I have the book 101 projects. Even though some stuff isnt what I think, it is a huge help to me. So far from doing some of the projects in this book I have learned a few things:
a 24 mm DEEP socket will not fit on the fan while the motor is in the car. it must be a "short"socket. Also, the $44.50 valve adjustment tool just doesnt work while the engine is in the car.

she smokes a bit during start up, espeically when cold, and when I stop at a light, meanign I have a few small leaks hittin those exchangers. I know a rebuild is in my future, but I was hoping to wait till next winter. I am watching the CIS to EFI conversion thread and thinking that, maybe 10.5:1 P/C set, and maybe even dual plug.

I beleive I have one pulled stud because when I pulled the cover off I found the nut loose in the head. when I went to tighten it back on I found that I could thread the nut all the way to the point I couldnt drive it anymore, ie the 10mm hex was pushed out of the nut. Not that I tried really hard, but I couldnt get the stud to budge at all with my poking and prodding. this makes me think it is pulled and not broken, not that that is any better if anything it is worse. What I found interesting is that I left the nut on the stud as far as I could thread it on the stud, closed it all up and took her out for a spin. the sound was gone, even when I really pushed the car hard. A day or two later, the sound came back. I am wondering if that nut has come off and if that is making the noise.

you folks on this board are definitely helpful to me. Unless you concider the hot roddign threads, which are the work of demons.....

Sin 1: Having a pulled head stud on a 3.0, normally it just breaks. Although that is not your fault.
Sin 2: Screwing that head nut down until it pushes the bit out, how are you going to remove it now?
Sin 3: Continue driving the thing and it will cause the heads to slap some more, the best that could happen now is you HAVE to have the heads fly cut, all of them.
Sin 4: knowing that it is slapping, you tested to board by saying that your schooling does not support the idea. The force is 150 psi multiplied by 8 square inches to be 1200 lbs of pressure on that head, 5000 times per minute, for as long as you drive it. Even a small a mount of deflection repeated that many times will cause issues.
Sin 5: I have a lot of schooling too, but I find that real life experience is better.

No one here has suggested that you continued driving that car. Maybe someone will, but that will still be in the minority.

If you are lucky, the stud may not be pulled. You can find out by getting a longer Allen and if the proper torque is obtained, without the stud coming out, it might be o.k. Also, if it is on the outside of #1,3, 4, and 6 cylinder, it is more serious because the combustion force will really want to deflect the heads. #2 and 5 are in the middle and enjoy the rigidity of the camtowers. In your case it is #1 exhaust side, not so good. :( It may very well be that, when you tightened up the first time, the stud pulled out more from the case and eventually pushed the Allen out of the barrel nut. Look at the other studs and compare the height within the nut. How many miles on the engine? Aside from Wayne's book, you may want to get a Bentley manual. SmileWavy

'Head-slapping' is an accurate description of the phenomenon ... but NOT of the sound it makes, which many describe as 'dog barking' and I tend to agree, if you specify a noisy mutt of the small variety, say, under 7 lbs!!!

If you want to witness the sound yourself ... get a trusted friend to drive the car by at 30 mph in 2nd gear, under throttle, not on overrun, while you are standing 40 - 50 feet away ... the sound is unmistakeable, just as produced by an air-cooled VW Beetle with pulled head studs ... driving by at low speed in 2nd gear!

I just have one question.

Why would you even bother closing up the valve covers when you know you have a head bolt that is not tight? Why would'nt you figure out a way to try and torque it or confirm a pulled stud? Why would you even assume that a nut that came loose on it's own would not come loose again especially when it's not even torqued properly? Why would you question that a noise related to a known problem is not a problem?

OK so I lied, it was 4 questions.

"A man goes to the Dr."
"Dr. it hurts when I do this."
Dr. says, "Don't do that."

Scott

1980 911 SC: Let us know how it turns out.