Broken Bolt in 1991 c2

[machisono]

Aloha all,

Found this broken bolt when changing plugs. What is it and how difficult to replace? Car has been running well.

Thank you in advance

Joe

[dporsche74]

head stud FULL rebuild in order a STOP driving NOW!!!

[964Play]

That is a head stud bolt. I just completed my first engine teardown and I had three of those broken. Best thing to do is to replace with steel studs. I cannot comment of how easy or hard is it to replace with the engine in.

[machisono]

thank you dporsche74 and 964 play, have you any experience with this tool:

EXHAUST HEAD STUD REPAIR KIT

joe

[RedCoupe]

Stomski makes nice tools. But, it looks as though your broken stud has a lot of meat on it to grab and screw out so I'm not sure that you need a tool to drill it out. The later aluminum case engines typically don't "pull" the studs like the earlier mag case engines did. Yours is probably a dilivar stud that broke due to salt air corrosion, and as mentioned earlier, it would be best to replace with steel studs. You will probably have other studs break as the studs made of Dilivar alloy are very sensitive to corrosion, so you may want to consider having all the lower studs replaced with new steel ones. The upper studs are most likely steel so should be okay.

[Hamptonsam]

Hi Joe,

The Stomski tool is for broken exhaust studs that connect the headers to the heads. Your issue is a broken head stud that holds the heads to the engine. I do not believe repair is possible without an engine out rebuild. If you only have one broken stud, it is debateable about continuing to drive. Some people say it is possible, but I assume you would not want to drive it hard. A rebuild is definitely in your future. I would remove all valve covers and verify that there are not more broken studs.

Duck

[machisono]

Aloha Duck and Red Coupe,

Thank you for the advice. I have the valve covers off and have inspected the studs and it is only the 1 on the first cylinder. I recall reading late into the night that these Dilivar studs are prone to corrosion and seem to break in relatively low mileage cars. I have only 58K on her and I drive her easy, it is actually too much power on a small island like Kauai.
Which was my reasoning for convincing the wife that a '68 912 would be the perfect island car

[RSTarga]

You can probably just do a top end rebuild. Bottom end should still be strong with that mileage.
You don't want to drive it like that because the cylinder will rub against the block and damage the seating, you'll then have to do a complete teardown.
It'll run from 6-10k depending on the shop and what needs to be done. If you don't have a good Porsche shop around , it might be better to ship the engine back to a good shop in California.

[aigel]

Definitely will NOT need a full rebuild at that mileage.

The task at hand is to disassemble the engine down enough where you can get the broken stud out. Of course all the others should be changed at the same time if they are Dilavar. I am not sure for your model, but on most engines only the lower studs were Dilavar as they see the most heat. Anyway, to get the studs out, the case can stay together and pistons and cylinders can be removed as a unit and re-installed undisturbed. I'd go this route on a 58k car. The heads, I would rebuild with new valve guides. This all said and done with new gaskets / seals and some odds and ends can be done for under $2500 DIY. Far from a full rebuild.

Good Luck!

G

[redturbo911]

Fix right away. Avoid any more damage.

[machisono]

Aloha Aigel and RS Targa,
Thank you for the comments. I agree, and this is the path we are heading down.

I have begun reviewing the various sites out there to find out what else should be done when the engine is out ( I want to avoid the temptation to go deep... if you ever remodeled a house you what I am talking about

I will replace the studs and thanks for the suggestions on new valve guides and various gaskets.

joe

[porterdog]

Originally Posted by dporsche74

head stud FULL rebuild in order a STOP driving NOW!!!

LMAO... I found one of those too, around 112k. I'll get to it eventually, but for the time being my car seems to be working well.

[aigel]

I am sure it'll hold up fine in some cases - but it does depend which stud it is - and how long the others will stay put. If you are ready to buy a few replacement jugs and heads, knock yourself out.

G

[machisono]

Hi Guys,

we're going for it. Got the 911 lift stand from a friend and am ordering the parts tomorrow. Thoughts on replacement studs? What about these Caspers that PP is selling?

joe

[Merle]

Supertec studs are what I'm going with when I do decide to rebuild mine.

[machisono]

Thanks Merle,
I purchased the Supertecs

joe

[Cobalt]

Just curious what head stud was this.

Of the ones i have seen they always seem to be on the exhaust side next to the plug, Was yours the same?

Also how critical is it to use the Porsche yoke when rebuilding? I have used others for 914 rebuilds and had no issues.

[machisono]

Aloha Anthony,

Also how critical is it to use the Porsche yoke when rebuilding? I have used others for 914 rebuilds and had no issues.

Intake side 1st cylinder.

A great many more members can answer your yoke question here on the forum. I have not decided whether I am going to leave it on the jack and operate about 20" off the floor, or get it up on a table.

[aigel]

The Porsche yoke or an aftermarket half moon shaped mount is essential to hold the case with even clamping force and not stressing the case mounting threads unevenly . And if you split the case, it is impossible to do on the stand unless you hold on only to one side with a proper mount.

G

[Garageboy]

No joke, get a yoke. Or at least the yoke ring like I did which fit right on a "normal" engine stand with a couple adapter sockets. The three prong yokes are too weak for a 964. Some things you can short cut, some you can't like riskin a cracked case.