Awwwwww man... How typical.. Head Stud gone?

Dana_Drury · 12-25-2002, 03:35 AM

Well after checking the torque settings on my lower nuts on Drivers side (RHD) (non exhaust side) I have noticed that one of the studs was slightly longer on the top rows of nuts... I pressed it with my fingers and it wiggled... So I assume that the head stud has broken. None of the others move.

A valve adjustment was done 6 months ago (and the car has only just been driven, probably a total off 200 K's) after the adjustment, and the stud was okay then.

I am pretty certain it is broken.

I have checked all the other studs (as best possible) and they are all fine. I guess you don't know until you pull of the valve cover.

If the stud is broken, I will need the engine rebuilt I assume, or at least what are my options?

k9handler · 12-25-2002, 05:19 AM

it's my understanding that one broken head stud is not the end of the world, and the engine will be fine for a while. The problem is when you have multiple broken head studs...so just take car with the motor and keep and eye on the studs, when the funds/time is right you can get the repairs done...i.e. case savers.

Some of the engine gurus will probably provide you a better answer.

my .02 cents worth!

yelcab1 · 12-25-2002, 07:48 AM

One broken headstud is not too bad. But, it is probably a sign of things to come. Whenever you can't stand it anymore and have the money, you need to pull the engine and do a valve job while you are at it.

It is normally bad karma to pull the engine just the replace the one head stud and put it back. Something else surely will go wrong shortly after that. So, replace all the exhaust studs (at least), put in case savers (not required), do a valve job (recommended), and change a bunch of seals if you have leaks (even if you don't have leaks).

Can you do this yourself?

Gunter · Gunter's Garage

What year? What size engine? Can you ge a socket in there to check the suspect? If the nut did not fall out, maybe it's just loose? If it's broken, can you get the broken portion out?

Dana_Drury · 12-25-2002, 02:09 PM

Its a 1976 3.0L Carrera Engine.

It had a rebuild about 10 years and 113,000 K's ago. I believe that the 3.0 Carrera engine had a the older Divlar (sp) head studs that were prone to pulling like the 2.7, I think headstuds may have been replaced if this one broke.

Unfortunately, the limit of my mechanical expertise does not extend to doing a top end job to my car.

Yes I can get a socket on there, I can pull the stud out, all though I only pull it out about 1cm before I freaked out...

Can the car be driven with one broken or lose stud?

Thanks for all your advice guys

k9handler · 12-25-2002, 02:12 PM

it can be.

yelcab1 · 12-26-2002, 08:39 AM

I know it is semantic, but the 3L engine is an SC engine, not a Carrera engine.

Second, the 3L engine is very prone to head studs breaking, and it is time to replace them if you had it that long.

Third, it will cost $2K-$3K to do it right, unless you can afford it now, you can drive it for a while longer until all the compression is gone. Be warned, you will do more damage driving it that way. How much more depends on how much driving.

Superman · 12-26-2002, 08:51 AM

Don't freak out. First, there is no such thing as lower, non-exhaust side studs. There is one row of intake side studs, and one row of exhaust side studs. It is the exhaust studs that break. I assume you are dealing with a head stud.

If you can pull the stud out, do so. It is not helping hold the engine together anyway. If you can do this, then it may have just backed out. If so, you can put loctite on it and screw it back in, probably.

A Carrera 3.0 is not the same as an SC.

I drove many miles on a broken stud. Yes, the cylinder head bounced on the cylinder top and got damaged, but that was the case with at least two other cylinders also, so I say go ahead and drive it. I suspect that a proper rebuild is likely to require flycutting the cylinders and heads anyway....regardless of your head stud experiences.

So, no big deal really. Again, I'd remove it if I could, and if it's in one piece, I'd reinstall it with loctite. Either way I'd drive the car and just plan a top end rebuild. Which you can do yourself except for the bench work (valves, machining).

Dana_Drury · 12-26-2002, 02:30 PM

Yeah the 3.0 Carrera engine is a slightly different beast to the SC. America didn't get them but Australia, Europe and Japan did. I am sure you have a number of grey imports of them in the US.

How do you know which side is which?

The side that broke is on in the top row (I think the 3rd), lower cover, of the passenger side (in a US car).

I was keeping an eye on it, but the thing fell out this morning with out me knowing, so I am not going to drive the car, get it over to a Mech and work out what to do.....

What a bummer, after waiting for a year to have the car ready, it decides to do this... hehehe... typical Murphy.

Gunter · Gunter's Garage

I would pull the stud out and see what's up. If it broke off, you can see how far down it failed. If the stud just came loose, put Loctite on and put it back in or let your mechanic do it. The stud is treaded on both ends. Your mechanic could also do a compression check all around which does not cost very much but will give you a better picture. If the stud is broken, watch for a noise like metalic clatter (Or gravel in a tin can) which means things are getting worse. (Possibly another stud) That noise is coming from the combustion in the cylinder making it past the compression seal on the head. As long as you don't have that particular noise, drive and do a top end rebuild in the future.

Just noticed you said it fell out. Is the barrel nut still attached? If it is the passenger side, is it exhaust stud for #5 cylinder? How much is left of the stud?

Dana_Drury · 12-28-2002, 09:10 PM

Excuse my stupidity, I know realise by exhaust side, you mean the lower valves are the exhaust valves, and the upper valves are the intake valves.

The thing must have snapped off fairly high up, and I think it is number 5 cylinder on the passenger side, I am not sure though.

I am heading to my Mechanics now, then I will have a better idea how to proceed. I haven't heard the gravel in a tin can thing yet, but I will keep and ear out for any noises out of the ordinary, but that's hard because it had been 6 months since I drove it.

Wayne 962 · Wayne 962's Garage

Odd, if the stud is broken, then it should simply fall out - not wiggle. I haven't heard of one, partially breaking. Also, I don't have information on these European cars - I'm not sure which studs they used in the 1976-77 European Carreras. I would guess that they used the Dilivar studs, as they did on the 1976-77 Turbos. The Carreras would only have them on the lower (exhaust side though).

The European Carreras were a 3.0L engine built on the 1976-77 Turbo platform. They were basically the precursor to the 911SC, and indeed are very, very similar. The biggest difference is the case and crankshaft. The Euro Carrera used the 2.7L crankshaft which has the same stroke as the 911SC crankshaft. The only difference is the flywheel mounting end, which is much bigger on the SC. These engines and cases, specifically, are highly sought after because they are the only aluminum engine cases that can run the smaller cranks. Thus, you can create a high-revving 2.9L engine (and thus skirt under class distinctions) by using a smaller crankshaft (like the 2.2) with the larger 3.0L pistons. I can't remember the exact combo off the top of my head, but that is why these cases are rare and desirable.

-Wayne

Dana_Drury · 11:53 PM

Sorry, I am such an idiot, computer geek's and cars probably shouldn't mix.

What has actually happened is that the stud that you screw the valve cover nut onto has snapped off. How it happened, I do not know.

I realise now that you can't even see the head studs until you pull the valve cover off (Is this this case?)

I was probably freaking out for no reason. I may have over tightened the nut while trying to fix the oil leaks we were having, and when the car got hot it expanded and snapped.

What are those short bolts called? And does anyone have a part number for me?

(I assume that I can now stop freaking out and actually laugh with my mechanic?)

yelcab1 · 12-29-2002, 09:03 AM

Those are called valve cover studs, and depending on which one it is, you can fix it with the engine in the car by drilling it out and reinstalling a new one. But it is location dependent. You could just drive it until the engine comes out for other reasons.

Let's hope your head studs are OK.

Wayne 962 · Wayne 962's Garage

Not a problem, everyone learns somehow. Check out this link:

http://www.pelicanparts.com/catalog/shopcart/911M/por_911M_enginC_main.htm

I'm pretty sure the studs are in there...

-Wayne

Dana_Drury · 12-29-2002, 01:31 PM

Thanks for all your help!

Gunter · Gunter's Garage

I think, a few people will laugh with you here. You must have really tightened that nut. I'll take a broken valve cover stud any day over a broken head stud. The nuts are "Nyloc" with Alu crush washers under them and when you order your next valve cover gasket kit, you'll get new ones. A good up-date would be getting 930-valve covers on the exhaust side. (Those are the lower ones) They make a better seal against oil leaks. Ask your mechanic if you have them already. If not, Pelican has them. Ask this board if there are any Pelican heads in your area. Somebody will be able to look at your baby and make recommendations on what to do.

Dana_Drury · 12-29-2002, 07:55 PM

Yeah I do have the turbo covers. Yeah I did tighten them to the 15lb/ft as recommended by JW (IIRC his post had that). I believe they are meant to be 8 NM or there abouts.

Basically the valve adjustment was done by my mechanic, the car was driven for about a week before being put on a 6 month stop while the entire car was rewired.

There must be some old gasket material letting the oil get through. I've order a new stud and a new set of gaskets.... lucky lucky... ahhahaa..