924Board.org

[924RACR]

This reminds me I ought to check mine for backing out, but anyway, might be time to throw some Nord-Loc washers in there? At least on the bolts...

Edit: just checked, they are available in Inconel 718. Specifically recommended for turbos.

Then again, finding someone to sell you less than a box of 200, at $6000USD or so...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Beartooth]

Well, here's what I ended up doing.



I installed inconel studs and Stage 8 stainless locking nuts. The studs are actually courtesy of Mazda: turns out the RX-7 uses an M10x1.5 stud. The part number is 9YA9-24-008. Also available is 9YA9-01-002; not sure what exactly the difference is other than the latter one is apparently 3mm longer. The part number for the locking nuts was STG-3952. Hopefully they're good stuff at almost $8 each ($30 for the set - comes with four). I couldn't tell you what flavor of stainless they are, but they are specifically for turbocharger applications, so hopefully not just 304. Another option is the Mazda nuts, JE10-40-355, at around $3.50 each.

I've always been a little unclear on how studs should be installed, so I just snugged them up a little to make sure they're seated. The moon clips were a pain to get on (especially on the bottom nut), but at least they should be easier to get off. I also used ARP stainless washers and nickel anti-sieze. It wasn't too big a deal to install all this without removing anything (well, I did have the charge pipe off, for what it's worth). That said, removing the exhaust would have made working on the nut on the underside a lot easier. Not much to report on for now; everything looks and works as well as I could hope. Anyway, I think I've sufficiently nuked this one: if there's a stronger, more heat-resistant manifold-to-turbo setup, I haven't heard of it, and it'd probably be fairly exotic (in material and price). I'm not sure what I'll find if/when it comes time to take it apart, but it shouldn't be a big deal since it originally had studs. So far, it's running great, and no problems I can see. Hopefully I won't have any more to report unless/until I have to remove the turbo again!
_________________
1980 931 diamond in the rough

[chuck21401]

Looks like a good (and much less expensive!) solution.

Will be interesting to see how it holds up over time. If the studs try to back out, they will not get far.

I have stage 8 locking nuts at the exhaust/turbo connection - they haven't moved yet.
_________________
1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

[Mike9311]

Dan had Stage 8 on all the turbo and exhaust connections for 10-ish years on the CS. I disassembled it and everything held up just fine
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Nofear924]

First time posting. I have 81 basket case im in the process of putting back together. Any update on the Mazda Studs and locking nuts? I'm missing the special bolts and sleeves. The engine is out of the vehicle right now. Turbocharger is basically what's left to be installed before installing it back in the car. I just can't justify $200+ for 3 bolts. That money can definitely go towards a lot of other things on the car. Appreciate any info for replacments.

[Cedric]

Not sure if I would put this in a separate post or in this one, but here is the reference numbers if anyone want to source the Scania bolts that i have been running for many years. Im not sure how many details I can share, but the material in the screw is very high spec, towards inconel, and they have a special coating. So is the sleeve, since the expansion rate of it is tuned so that it keeps clamping force when the whole thing heats up. I dont know what they cost though, i use the bolt+Sleeve in all three positions, although the back bolt have to be cut down, the sleeve aswell to improve acess.

From the 730hp V8 engine, there is a service network in the US aswell for industrial engines, not sure they will sell parts to anyone though.

1922517 Screw
2030496 Sleeve

I only use the flange screw+sleeve, forget about the other bolt.

_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Beartooth]

So far, so good with the Mazda studs and Stage 8 nuts. I'm only around 1000 miles on it, and haven't pushed it that hard (my motor badly needs a rebuild), so it's not a thorough test. The difficulty of getting the parts Cedric suggests is the only reason I didn't go that way; the Mazda pieces are easy to get from a dealer or online. If somebody finds a US supplier, those Scania pieces sound perfect. I'm not sure what to say about my first attempt with ARP chromoly bolts: one did tear part of a thread when I pulled them, but otherwise they held up fine. That was using copper antisieze; I switched to nickel-based stuff when I put the studs in, and that seems to be the best choice for turbine fasteners.

Stainless bolts might be an option (available from ARP), but they're more prone to galling. There is a lot of stuff out there from aftermarket companies that would work - Ti, stainless, inconel - but it could be poorly-made, so you really have to consider who it's coming from. I don't think any of the aftermarket stuff was any cheaper than the Mazda studs and lock-nuts, which are probably as good or better. For $35 (plus $5-10 for stainless washers and nickel anti-sieze), the Mazda studs and nuts might be the best bang for the buck. Ideally, you'd replace the lock-nuts every time you had it apart though. I do wonder what the thought behind the Porsche bolt and sleeve setup is. Maybe there's a good reason to run them, or duplicate them, but having them back out kind of negates any advantage (especially at $70 for a replacement bolt and sleeve).

Ultimately, I'd say you're fine running any quality inconel hardware that fits and clamps properly, or as a second choice, other materials if it's OE turbo hardware or from a good company and specified for turbine flanges. Also, the details are just as important as the pieces you use. Chase threads with a good thread restoration tool (a tap should work too, although I've heard that can cut away thread material). Really take your time getting the alignment right, and take a step back if something doesn't look right. I'm no expert, all I can say is I've done a full turbo R&R and it seemed to come out ok. It was a PITA - it was easier pulling and tearing down my snowmobile's engine (and I'm not practiced at that) - but the tips I found here helped a lot.
_________________
1980 931 diamond in the rough