Broken Head Studs !
08-05-2005, 08:28 PM
#1
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Broken Head Studs !
I was able to get the engine down to the long block today and found the first culprit....# 4 and # 5 upper head studs broken! I guess the factory had good intentions when they installed Dilavar but it's apparent that they don't work.
08-06-2005, 12:50 AM
#5
RL Technical Advisor
Originally Posted by jwl
I guess the factory had good intentions when they installed Dilavar but it's apparent that they don't work.
Dilavar's expand at the very same rate as these alloy engines do and in the case of Turbo motors, thats a good thing due to the greater degree of expansion these undergo.
Although ARP head studs are a very good product, we prefer to use the latest 993 RSR (and TT) Dilavar studs on Turbo motors since they do a far better job of retaining uniform torque on the head nuts, regardless of temperature.
I've seen too many loose ARP head nuts (some fallen off) to trust them on 930's anymore.
Just my 2 cents, tho.
Last edited by Steve Weiner-Rennsport Systems; 08-06-2005 at 02:05 AM.
08-06-2005, 12:57 AM
#6
Rennlist Lifetime Member
With all due respect I have not heard anyone recommend that. I confirmed with Bruce that both he and I have seen the new generation delivars snap. Just like the old ones. If you have head studs that are loosening up something is being done incorrectly on install such as suggested torque and or pattern of tightening. Lastly the proper lubrication is very critical. I have checked motors I have built 6 years ago and never had one loosened up. Both ARP as well as Raceware and others are a better choice than Delivar. On motors that are stock simply use the standard steels.
08-06-2005, 02:03 AM
#7
RL Technical Advisor
Originally Posted by PorschePhD
If you have head studs that are loosening up something is being done incorrectly on install such as suggested torque and or pattern of tightening.
Having built Porsche race engines for the past 30+ years, I've not experienced any loosening of head nuts (even on 935's which are really highly stressed engines) except for some ARP's and all were properly installed, lubricated and torqued.
Although I'm not arrogant enough to say that it will never happen, I've not had any issues with the RSR studs since we began using them in '94 so until I have one snap, they work for me.
Bottom line? We are all the result of our overall long-term experience and some folks simply differ in that,....
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08-06-2005, 11:08 AM
#8
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This will have to be one of the things we agree that we disagree. Interesting enough a few years back you said Jeff didn't like the Raceware studs. I have seen it several times where the heads are not rechecked after the torque sequence is initially done. Meaning not double checking your work or triple checking your work. If one's own work is re-checked and the pattern is done in the correct manner I have yet to see a single stud loosen as suggested. Now we also always recommend on our builds to retain warranty to retorque after 1K mikes. Averaging about 5 motors a month I would say that the data collected here is pretty good. Track motors that run a season and street motors that run a lifetime are two different things and certainly come from a different frame of mind.
Actually because of the threading process these are not that strong and have to start life out as a much smaller stud. Therefore the reason for breaking. As confirmed by myself and several in the national tech committee. We have a pattern here. The stretch properties as tested were not impressive and when we tested the others they showed better expansion properties than the factory units. When tested the after marketversion expansion was far closer than any of the stock versions. Why would we test head studs you ask. Well lets say just keep an eye out..
Dilavar's expand at the very same rate as these alloy engines do and in the case of Turbo motors, thats a good thing due to the greater degree of expansion these undergo
