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chuck21401
Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD
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Posted: Mon Sep 23, 2019 6:08 am Post subject: Missing bolt - exhaust manifold to turbo |
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Was looking under the hood today and noticed that I'm missing an important bolt. Yikes. Guess the good news is that the bolt head didn't snap off. So either it backed out of there or wasn't reinstalled when the turbo was bolted back on?
Looking at the parts diagram...I'm missing the bolt (931-123-197-00) and sleeve (931-123-199-00). Only $75 from the dealer.
The other bolt that I can see doesn't seem nearly as exotic...it is holding down a regular washer rather than a sleeve. Wondering if I could use generic metric hardware here.
_________________ 1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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924RACR
Joined: 29 Jul 2001 Posts: 8815 Location: Royal Oak, MI, USA
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Posted: Mon Sep 23, 2019 9:49 pm Post subject: |
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Yeah, relatively generic would be fine - though I'd aim for grade 8.8 at least. And for sure a lockwasher, those bolts like to come loose. _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Cedric
Joined: 27 Aug 2004 Posts: 2614 Location: Sweden
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Posted: Mon Sep 23, 2019 10:56 pm Post subject: |
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I would say try to avoid generic hardware, its a bad idea for the turbo joint. These bolts are very high spec, especially on turbo engines, since normal steel bolts loses alot of clamping force with the heat. The spacer i also important as it need a material which expands in similar fashion as the other materials in the joint the keep the clamping while its hot.
The prices are mad on these bolts from porsche. I have used turbo bolts and spacers from Scania 730 truck, since I know the spec on those (I worked with this years ago), but you dont have those over there.
An alternative is to just look at other OEMS and tryck to find similar screws from other turbo joints (All OEM turbo screws are most likely fairly high spec). Thats how i bought my exhaust manifold-head studs, waste gate studs and nuts etc, its all from the VAG exhaust parts catalouge. _________________ 1980 924 Turbo
www.instagram.com/garagecedric/ |
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Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
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Posted: Tue Sep 24, 2019 3:41 am Post subject: |
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I broke 2 of the 3 of them the first time I removed my turbo and then ran grade 8 black allen head bolts for a while..
I was able to acquire 2 more turbo bolts in parts lots I have bought here over time and have been running with 3 original bolts for a while now..
I'd try to buy them from guys here that have parted turbo cars if I was you.. Or what Cedric said is a pretty good idea too.. _________________ 80 Turbo - Slightly Modified |
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chuck21401
Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD
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Posted: Tue Sep 24, 2019 6:11 am Post subject: |
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Thanks for the comments and ideas. I think I'll buy the Porsche parts to replace the missing bolt and sleeve. I'm just not going to tell my wife how much I paid for them.
Good idea about buying them when turbo cars get parted out. I found some old classified ads on Pelican and Rennlist when I ran searches on the part numbers. So I'll replace the other two bolts over time. One bolt looks easy to remove and replace, the other one was obscured by the exhaust manifold...hopefully that one is accessible without removing the engine or something.
I found a picture of the bolt in the classic porsche parts catalog, the other bolt installed on my car doesn't look like this. Ack. So I'm guessing I need a special metric 12point socket to tighten the bolt?
_________________ 1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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Svobodin
Joined: 08 Oct 2013 Posts: 67 Location: Colorado
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Posted: Tue Sep 24, 2019 6:50 am Post subject: |
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On my 1980 931 two of those were studs and the obscured one was a bolt. Guess they updated that for 1981.
I will say those bolts/studs were probably the worst part of replacing the turbo. Could not get them to align at all (stud came out with the nut so essentially acted like a bolt) while holding the turbo up at the same time, not fun! |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Tue Sep 24, 2019 8:25 am Post subject: |
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I swapped my OEM 12 point bolts of some fancy material for 3 high quality studs with Allen heads to help tighten, reused the 3 OEM inconel or similar sleeve washers which are NLA, all tightened with high quality stainless lock nuts. Survived 4yrs of abuse before being replaced again earlier this year when swapping out the turbo. The replacement studs and nuts were circa £50 a set. The OEM 12 point bolts are circa £30 each. They are not regular steel. _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252 |
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924RACR
Joined: 29 Jul 2001 Posts: 8815 Location: Royal Oak, MI, USA
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Posted: Wed Sep 25, 2019 3:30 am Post subject: |
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Dunno about the sleeves, I must be missing them, but perhaps some fancy ARP stainless bolts would work well:
https://arp-bolts.com/kits/arpkit-detail-b.php?RecordID=3529 _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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chuck21401
Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD
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Posted: Wed Sep 25, 2019 4:15 am Post subject: |
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I ordered one set from Porsche. Will wait on replacing the other two. _________________ 1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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chuck21401
Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD
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Posted: Wed Sep 25, 2019 4:31 am Post subject: |
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Nice find. The Porsche bolt is listed as 10 X 37 in the description. I'm guessing that the sleeve is in the neighborhood of 7mm. Will take some pics when the exotic parts arrive.
I think the original bolt must have worked its way loose. _________________ 1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
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Posted: Wed Sep 25, 2019 6:06 am Post subject: |
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The manifold to turbo bolts make a break for freedom at every chance possible _________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252 |
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chuck21401
Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD
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Posted: Wed Sep 25, 2019 10:17 am Post subject: |
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chuck21401 wrote: | I ordered one set from Porsche. Will wait on replacing the other two. |
Ack...update from the dealer.
Thank you for your order. Unfortunately part number(s) 931-123-199-00 is being sourced from Germany. Standard shipping for this item will take approximately 4-5 weeks to arrive
So will order the ARPs to hold things together for now. I also need to crawl under the car to see if anything else is loose. _________________ 1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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924RACR
Joined: 29 Jul 2001 Posts: 8815 Location: Royal Oak, MI, USA
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Posted: Wed Sep 25, 2019 9:56 pm Post subject: |
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Ew!
Yeah, I had a bitch of a time trying to get everything to stay tight. Stage 8 kit worked well, but corroded unpleasantly with the heat - pretty much had to pitch it all when I took it apart. Last round of assembly was using stock copper lockwashers from Bel-Metric... haven't had a lot of miles since, though, and that was only this summer.
I do find it amusing that there's even a procedure in the factory manuals on how to check torques on the turbo downpipe studs/nuts... _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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chuck21401
Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD
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Posted: Sun Sep 29, 2019 4:56 am Post subject: |
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The ARP bolts worked out well.
I replaced the missing bolt...and realized that the other bolt was finger tight!
So I replaced that one too. _________________ 1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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chuck21401
Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD
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Posted: Mon Oct 07, 2019 5:11 am Post subject: |
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Update - another bolt disappeared and the second one backed out 3/4 of the way. I was using lock washers.
The good news is that the missing bolt was ARP and not the special bolt/sleeve ($$$) that I ordered from Porsche.
What else could be going on here? Both bolts tightened down as they should so I don't think that the threads are stripped. Maybe the turbo isn't tight enough and is shaking things loose? Also don't know about the third bolt or stud behind the exhaust manifold. _________________ 1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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