911SC Broken Head Studs
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Rennlist
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Rennlist
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Joined: May 2001
Posts: 5,864
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From: TX
911SC Broken Head Studs
This has been discussed recently, so while at the Rennsport Reunion I collared Bruce Anderson and discussed this. We know about the problems the 2.7L engines had with head studs pulling out of the case - this has been well documented.
Thankfully, we don't have that problem on our 3.0L engines, however, we do have problems with lower stud corrosion, which can lead to broken studs. There were several varieties of Dilavar studs which tried to address this problem, however, by the time the factory was rolling out the last air-cooled 911's, they were using two varieties of steel studs.
One way to test for broken studs is through a leak down test, which should be part of a pre-purchase inspection. Bruce recommends replacement with either Raceware or the factory steel studs. Since this problem doesn't involve dissimilar metals expanding at different rates, as with the 2.7L, the factory steel studs are an OK replacement. Bruce's take was that this corrosion may affect a significant number of 911SC's over time.
Thankfully, we don't have that problem on our 3.0L engines, however, we do have problems with lower stud corrosion, which can lead to broken studs. There were several varieties of Dilavar studs which tried to address this problem, however, by the time the factory was rolling out the last air-cooled 911's, they were using two varieties of steel studs.
One way to test for broken studs is through a leak down test, which should be part of a pre-purchase inspection. Bruce recommends replacement with either Raceware or the factory steel studs. Since this problem doesn't involve dissimilar metals expanding at different rates, as with the 2.7L, the factory steel studs are an OK replacement. Bruce's take was that this corrosion may affect a significant number of 911SC's over time.
Pro
Joined: Jun 2001
Posts: 556
Likes: 1
From: Peoples Republic of Long Beach, N.Y.
My 2.7 was completely rebuilt in my library. Time-certs is a simple 4 step process, I believe. Anyway, the case was sent 3,000 miles to Bodfish, Calif. via UPS, to have a P-pro machinist do the install. Raceware studs and rod bolts were used. Cheap insurance, I need bullet-prof for big rides. The best way out is always through.......Ron 
Intermediate
Joined: Jun 2001
Posts: 26
Likes: 0
From: New Smyrna Beach, FL.
I can personally attest to this issue (broken due to corrosion) with the 3.0 head studs, specifically the lower ones. Mine had 5 broken when I pulled the engine for rebuild 
I used factory steel studs and replaced all the lowers. Those of you with 3.o engines that are getting long in the tooth may want to consider checking your lower head studs next time the lower valve covers are off. Just shing a flashlight in would be a good start, if not putting a socket on them and checking for any looseness. Just a FWIW. 
I used factory steel studs and replaced all the lowers. Those of you with 3.o engines that are getting long in the tooth may want to consider checking your lower head studs next time the lower valve covers are off. Just shing a flashlight in would be a good start, if not putting a socket on them and checking for any looseness. Just a FWIW.
Racer
Joined: Jun 2001
Posts: 486
Likes: 8
From: Scottsdale, AZ
I had broken studs about 9 years ago and replaced with dilavars. They have been holding on, but if I were to do it again I guess I would go with the factory steel or raceware instead of the dilavars considering the bad reputation they have as of late. I wonder if the factory steel/raceware is the popular choice now along with phosphorous bronze valve guides. There have always been different opinions on these subjects so some clarification is definetely welcome.
