Broken Cylinder Head Stud
Thread Starter
Instructor
Joined: Jan 2010
Posts: 134
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From: South Bay, California
Broken Cylinder Head Stud
I finally had the guts to adjust my valve's on during the weekend. Although I haven’t had the chance to start her up because I'm still working on swapping exhaust for new SSI's and M&K duals. I found a broken cylinder head stud lying by number three cylinder. Don't know when this happened. I don’t have any engine performance problems that I know of the cars runs good and strong. Here are my questions.
What will happen if I don’t fix the stud?
What will it take to fix this problem?
What will cost?
I have lots of carbon build up on exhaust cylinder 1&3 and the rest are clean.
What can I do to clean the carbon?
What will happen if I don’t fix the stud?
What will it take to fix this problem?
What will cost?
I have lots of carbon build up on exhaust cylinder 1&3 and the rest are clean.
What can I do to clean the carbon?
Rennlist Member
Joined: Jul 2002
Posts: 16,557
Likes: 94
From: Bend, OR
Allowing the motor to continue to run like this will cause sealing issues down the road. The damage may, or may not be able to be repaired by machining mating surfaces.
If you have "one" broken stud, how long before more? At a minimum, you need to strip the engine down to the case-replace all headstuds. As part of the deal, you can have the heads done, rering the pistons (although you post NO info on year/engine), remove the carbon, and reseal the motor from the case out. I'd guess $4-6K.
This is where Porsches aren't inexpensive.
If you have "one" broken stud, how long before more? At a minimum, you need to strip the engine down to the case-replace all headstuds. As part of the deal, you can have the heads done, rering the pistons (although you post NO info on year/engine), remove the carbon, and reseal the motor from the case out. I'd guess $4-6K.
This is where Porsches aren't inexpensive.
Burning Brakes
Joined: Oct 2004
Posts: 1,056
Likes: 1
I found a single broken stud on my 78 SC and decided to park it until I fixed it. That was about three years ago now. Damn, I need to get started. My plan is to replace just the twelve exhaust side studs. Still debating whether to do a valve job. Probably will depend on what I find when I get in there.
Brett
Brett
I haddah Google dat
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Joined: Nov 2008
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From: Fresno, CA
This is one of those :::sigh::: things about 911s. You can drive it, but as stated you're ruining that cylinder and (worse) probably the head. If you hear a blapblapblap sound at high rpm, that's the head flapping around against the cylinder.
Thread Starter
Instructor
Joined: Jan 2010
Posts: 134
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From: South Bay, California
I want to give everyone update of what I have discovered the cost of repairing this problem on my 1978. All the shops I’ve talk to mentioned this is a somewhat common problem in all air cooled pre- 993. Everyone said nothing will happen for a while, but eventually the cylinder head will start to leak, and worse case you will begin to have compression leakage. You guys mentioned that this could damage the cylinder heads. All the shops agreed to cylinder head damage but it’s uncommon unless the car’s used in high revving drive such as the track. That being said cylinder head damage can also happen without broken studs in racing application.
To repair it, the heads have to come off and all studs replaced or engine rebuild, so not a cheap fix. The least costly repair I was quoted $2500 to replace all the studs and up to 7K for a complete rebuild. Three shops quoted 7 – 9K to replace the studs and valve job and another ask for 11K to do the same job. Four of the five recommend it needs to be done right away.
The cheapest shop recommended that if I don’t have fund’s right away that it can wait. He also recommends that if I plan to fix the studs alone that I should wait till I can have the engine rebuild for 7K. His logic it takes them almost the same amount of labor to replace the stud and rebuild the engine but I will have to pay more parts. This solution would give me a better long lasting engine better than my original 28yr old engine. So I decided to wait and check the engine annually for more broken studs. When the condition gets worst I will have no choice but have the engine rebuild.
To repair it, the heads have to come off and all studs replaced or engine rebuild, so not a cheap fix. The least costly repair I was quoted $2500 to replace all the studs and up to 7K for a complete rebuild. Three shops quoted 7 – 9K to replace the studs and valve job and another ask for 11K to do the same job. Four of the five recommend it needs to be done right away.
The cheapest shop recommended that if I don’t have fund’s right away that it can wait. He also recommends that if I plan to fix the studs alone that I should wait till I can have the engine rebuild for 7K. His logic it takes them almost the same amount of labor to replace the stud and rebuild the engine but I will have to pay more parts. This solution would give me a better long lasting engine better than my original 28yr old engine. So I decided to wait and check the engine annually for more broken studs. When the condition gets worst I will have no choice but have the engine rebuild.
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Joined: Jul 2002
Posts: 16,557
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From: Bend, OR
The guy quoting $7K for a "complete rebuild" is one you do not want to deal with. He's either lying about it being "complete, will be cutting MANY corners, or has no clue. He doesn't have a company called Motor Meister, does he??
I've seen more than a few pics of damaged heads from driving them with broken studs. The race track has no bearing other than it may happen sooner.
It's your gamble...
I've seen more than a few pics of damaged heads from driving them with broken studs. The race track has no bearing other than it may happen sooner.
It's your gamble...
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Thread Starter
Instructor
Joined: Jan 2010
Posts: 134
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From: South Bay, California
His in Madison, WI and one of premiere Porsche motorsport shop in WI. There heavily involve in Porsche racing here in the Midwest and around the country. I've seen one car he has work on a 1989 with a 993 twin turbo engine conversion. Although I have no personal dealing with this shop yet. Is there any reason 7K is a sign of bad work?
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Rennlist Member
Joined: Jul 2002
Posts: 16,557
Likes: 94
From: Bend, OR
I highlighted the words Complete Rebuild. A shop cannot do that for $7k, unless they do charity work. Maybe you assumed, or maybe they need to give you a detailed estimate in writing. My guess is that is only a topend rebuild, and I'd question whether it includes new P's & C's, and what kind. Rebuild means a lot of different things to different people. I believe most quality full rebuilds by pros are in the $13k neighborhood.
