5 pulled head studs

[Vincent 911]

Bad news tonight for me: I removed the 2 lower valve covers for the first time on the 911 SC to do the valve adjustement and see the disaster.

Total of 5 heads studs broken:
- 4 on driver's side
- 1 on passenger side

This is my first 911 (I had previously a 912). I bought 1 month ago. I am updating / upgrading it: carrera chain tensionner (changed yesterday evening), SSI's, Dansk muffler, Bilsteins, new tires, interior...
It will be my week end driver and sometimes go on track (like my previous 912).

I also found this strange part (see picture). I am thinking about a valve stuff. Any Idea?

So I will remove the engine this week and start to change these head studs.

Before this bad new I planned to changed pistons for higher compression ratio ones and regrind camshafts with 964 profile. I want to keep the CIS fuel injection system.
It will be my first engine rebuilt. I will do all the job on my own for

Should I order 9.5 or 10.5 pistons?

Do I need to change valves? What parts do I need to order?

Thanks for all. I will kep you updated.

[88-diamondblue]

I know the feeling, it sucks big time. On the other hand the rebuild is a great project.

That is a half of a valve spring retainer

[Porsche-O-Phile]

So remove the old studs, get inserts, put in new (better) studs and go on with life. C'est la vie. Not the end of the world.

[gabenheimer]

Ditto on the valve spring retainer. Since you have the later aluminum block, you may not need case inserts for the head studs. Getting the broken studs out can be (will be) difficult but not impossible. There are plenty of posts out here detailing the correct technique for removing Dilivar studs. It can be done, just take your time.

[Jeff Alton]

I see your low post total, so let me start with.......... Welcome to the forums! You will find lots of great advice here.

The part in question is a valve keeper, well one half of one.

If you were planning on opening the engine up anyways it really does not matter if you have none, one or many broken head studs. Yes, it is bad news, but if you were going in there anyways.....

So, here is what I would do (and have done a few times with 3.0 SC motors).

Post your questions and then progress on the "Engine rebuilding Forum"

have built a few a few 3.0 motors and for a nice subtle upgrade without braking the bank (with smog in mind) here is what I would do.

replace all dilivar studs with factory steel studs.

Put the 964 cams in that you mentioned. (or web 20/21)

I can't tell from your post if you have the SSI's or are planning them. At any rate, get them.

If your P/C set is in spec, leave them alone. For a single plug 3.0, I would not go above 9.5 CR for pump gas.

Get a good VITON gasket kit (not sure if Pelican has them or not, but I can point you to those that do)

Now, if your P/C set is out of spec you have a couple of options. If on a budget, I would build a Short Stroke 3.2 with JE 98mm pistons and bored/plated 3.2 cylinders. Or maybe look at a set of new QSC cylinders and JE pistons from Supertec. Apparantly he measures all the cylinders for QA and makes sure they are correct......IF you want to spend some cash and get a really high qualitly product, I would look to LN engineering for a set of 98mm Nickie cylinders with matched JE pistons.

This will build a pretty potent motor even with the stock CIS injection.

Have FUN.

I have put a few 3.0's together with 964 cams and they are great motors. Throw on a set of SSI's and they are that much better. One of the motors I did lives in California and passes smog with no troubles at all.

Like I said earlier, if you planned on openning up the motor anyways, a few broken head studs is no big deal.

Cheers

[Vincent 911]

Thanks Jeff.

So I will take my time and post pictures.

I plan to remove the engine on saturday.

I am only 24 years old and my budget is not extensible. Therefore I will go for the cheapest parts... Which of the 2 following options is the cheapest?
- have my camshafts regrind with 964?
- get a pair of 964 camshafts?
- get a pair of web 20/21?

For the pistons I will wait and check if they are in the tolerances.

I have already the SSI's and a soprt 2 inlet / 1 outlet Dansk muffler.
Carrera tensionners are already installed.

Thanks for all.

Vincent

[David]

There's a good chance you have Alusil cylinders, in which case you probably should not change the pistons or rings unless you also change the cylinders. Spend a few hours searching the forum and you should tons of info (and opinions) on what options you have.

[john walker's workshop]

the longer broken studs leave just a short stub remaining in the case. they will be your biggest concern. not much to grab and if you chew them up trying to grab them with visegrips, you will lose the one chance you have of getting them out. being that you're not really familiar with this procedure, it may be wise to seek professional help on them.

[Superman]

I'd agree with John. Of course. He guided me through this procedure, and I had plenty of stud to grab onto. The thing is, the studs are glued in with red Loctite. That means you have to get those internal threads HOT. Propane will not come anywhere near the temperature you will need. When the oxy-acetylene flame gets them hot enough, you can feel them release. Keep heat on and turn them out without stopping. Like John says, this would be an excellent task to hand over to a local seasoned professional.

I would disagree with the notion that Alusil cylinders shouldn't be reused. That's the conventional wisdom, but it looks as if you are likely to have good luck doing it. I did. If you searc the Engine Rebuild Forum for an "Alusil" thread, there is one in there that's VERY long and VERY complete and inclusive. More than you ever expected to know about cylinder design.

[ianc]

Agree on reusing the pistons and cyls if possible. You will not be able to get above 9.5 on pump gas, and the stockies are 9.3 I believe?

Do not neglect the heads. You will want all new valves if you can afford, and the exhausts if you can't. Get new guides installed and the seats cut. You will want to farm this portion of the work out to a reputable Porsche mechanic.

Good luck with it!

ianc

[Jeff Alton]

Vincent,

For the cams I would have your SC cams reground by DRCamshafts. John is member here and does great work. This is the most cost effective of the choices you listed.

I have re-ringed one alusil 3.0 and it is fine. Mind you I sent the cylinders out for the recommended 3 step Sunnen honing process first.

Only re use your P/C if they are in spec! It goes without saying, but that gets lots sometimes.

Cheers

[Superman]

You don't hone Alusils. My recommendation is to clean them within an inch of their lives. You want to get all the carbon and whatever out of the somewhat porous or at least 'profiled' surface so that the silicon bits can interact with the rings in the way they are supposed to. Honing surfaces the silicon, so that method is not ideal. Again, the thread on the Engine Rebuild Forum (I think it is entitled "Re-Ringing Alusils") goes into excruciating detail about the differences and functions of Alusils versus Nikasils.

I would certainly agree that they need to be in spec. They very likely will be. The most wear I could find at any point on any of my six Alusils was .0015". That is WELL within spec.

I would also agree that it's time to work the heads. New valves, particularly the exhaust ones. All valves, really. Intakes are cheaper. New guides (new valve guides are far better than your stock ones, which are likely worn). Professional seat cutting and lapping of valves. This is the part that will cost you. You'll spend something like $3K in all, most of that on the heads. That's if you're very frugal.

[Jeff Alton]

Umm, there is a special Sunnen process endorsed by KS to make them work. It uses a honing maching and special abrave pads and compounds. Or, I guess you could just clean them like Superman did.

Re-ringing any cylinder can be a crapshoot, but chance are good you will be successful.

Cheers

[Superman]

I got input from the Great and Powerful Bruce Anderson, as part of my decision to re-ring the Alusils. His advice was simple and brief. Do not baby the new rings. MAKE them seat. So.....I used a teensy weensy bit of oil during assembly. The jugs were basically dry, except that there was enough oil on them to potentially be detected using extremely sensitive scientific testing equipment. When I started the motor after the rebuild, I had the timing light already hooked up and the clamp nut loosened. I checked the timing quickly, tightened the nut, threw the light onto the lawn and then pretended I was driving a stolen car in a police chase. There was never any smoke. They seated immediately.

[Jeff Alton]

I agree with your break in procedure. Can't baby it.

Cheers

[Moke81]

How can you tell if studs are broken if you don't pull the covers?
______________
1981 SC Coupe

[john walker's workshop]

on hard acceleration, the engine sounds like an old vw getting it on down the road. pop pop, pop, pop, pop.......
kind of like a hole in a muffler, repetative popping, in various degrees, some subtle, some not.

[Porsche-O-Phile]

Tip for extracting broken studs or bolts:

1. Get a Dremel with a cut-off wheel

2. Cut a "notch" or "slot" into the end of the remaining piece of stud (this assumes, obviously that it's broken above the adjacent surface enough to do so)

3. Use a screwdriver to extract (you've just created a standard screw head on the broken bolt/stud shaft).

This tip works great on studs that you've destroyed the threads on with vice grips, as someone alluded to. It takes a little technique but I've used it many times.

[ianc]

Another tip (if you have the proper equip) is to weld a nut onto what's left of the stud. After heating up the stud end where it goes into the case, you should be able to turn it with a socket,

ianc