300ZX Turbo to Downpipe Bolts
 

I've recently torn down my install after about a year and a half and 15000 miles of driving. A head gasket with 200K miles on it was the catalyst.

In addition to the head gasket, it became obvious that I need to change my hot-side connectors. The mild steel bolts that I had used for manifold to turbo were completely inadequate. On had sheared in use. The other three had bad cases of thermal creep (turbo was loose) and sheared during removal. Only the safety wiring was keeping things together. TSE's M10 x 1.5 Inconel studs are now going in to take care of this area.

I used similar safety-wired mild steel bolts for the turbo to downpipe connection. These held up, were tight and came out undamaged, although the zinc corrosion coating was long gone. They see a lot less heat than the manifold to turbo area. Nevertheless, I'd like to upgrade these as well and have been looking around for suitable bolts. During my internet searching, I came across the factory early-90s Nissan 300ZX turbo to downpipe bolts. Supposedly, these were Inconel. Does anyone know anything about these particular bolts? Material (for certain)? M8, M10, other? Thread pitch? I can't seem to find these details anywhere.

Thanks in advance guys. If these really are Inconel M8 x 1.25 for $5 each, it would seem like a sweet solution.

I remember reading that Nissan used inconel bolts/studs on the Skylines and perhaps a few other cars. I'm sure they won't be M10, but a street car should get along just fine with inconel M8's.

Bolts Came In
 

So, I ordered the bolts (1990-1996 Nissan 300zx OEM Turbo to Downpipe Bolt).

$3.50 each!

The picture shows what I got. M8x1.25x28mm. Inconel. Nissan OEM. I think these are going to work really well. Happy with the purchase.

Easily drilled for safety wire, so long as your drill bit is sharp. The bolts do dull the bit quickly. Once it starts chipping rather than cutting, toss the bit. I've been using about 1.5 bits per bolt (I ordered 8 bolts).

Wouldn't use these on the manifold to turbo connection -- you want studs there for disassembly (got TSE's kit). But these should be just the ticket for the turbo to downpipe.

Bump

Great information Rick. +

Encouraged by your success I went to my local Nissan dealer and ordered some 300zx studs. It seems in addition to the bolt you ordered there are 2 additional types of inconel studs used on the 300ZX turbo setups.

https://www.miataturbo.net/attachmen...ine=1408734962

1406440P01 is around 31 mm long and is the one used on the t2 flange. 1441417F00 is around 35mm long and is the one used on the downpipe flange. As far as I know they are inconel as
1) The Nissan man said the are
2) They are non magnetic
https://www.miataturbo.net/attachmen...ine=1408734962

Originally the t2 side nuts look like they were locked in position with lock tabs. This shows the 1406440P01 part mounted on a t28 manifold.

https://www.miataturbo.net/attachmen...ine=1408734962

I will test these and update with the results.

I should add that long-term, I've had good service from the Nissan turbo-to-downpipe bolts. I've disassembled/reassembled easily a couple of times over the last two years and been able to reuse the hardware with no issues.

If anyone is looking for alternatives, I used Mazda rx7 FD bolts, which are also m10 and also inconel, and also work great.

This stuff should be bueno for any 2554/2560/2860, etc?

thanks for the long term report. i am in the middle of trying to find cheaper alternatives to TSE, and finally just broke down and bought some inconel bar and im having it machined by a friend. i may still get some of these for the DP though

I also used a set of the Nissan ones for my turbine housing to exhaust manifold on my MSM and they haven't budged within almost 2 years. I was able to spare at least 4 of the original nuts that were on the MSM turbine/DP setup and used them with these studs.

Good information Vlad. I guess the part no for these Mazda studs is 9YA9-21-003? They look like they are regular M10 x 1.5 mm thread pitch.
95 Rx7 Large Exhaust Manifold to Turbo Stud...


If M10 x 1.25mm pitch is needed then Subaru 800910340 are an option.
https://www.miataturbo.net/attachmen...ine=1408915286

We used the 300zx studs and stage8's on billybobsters turbo to downpipe and a TSE manifold to turbo kit. Its been 2 seasons now? they are holding perfectly. also bracing the downpipe probably helped a ton.

Yep, thanks for the part#. I always forget to look that up. Depending on which turbo you use you sometimes gotta trim them - they're about 10mm too long.
And yes on the subaru studs too - I've actually used those too with no issues before. Though I'm not sure those are inconel - at least I never noticed that word in any of the part names or descriptions.

I was using the Inconel M10 stud kits from Full Race as a less expensive alternative to TSE, fwiw.

Yep, 300ZX turbo to manifold studs here. Holding up well. I need to remember to recheck my nuts again and see if the copper ones backed off. If they did it will be time to order the M8 stage 8 fastener kit on amazon for cheap.

Also, these may work for an M10 option. One of the other RX-7 studs.

9YA9-01-002

Leafy Make sure the kit has steel tear drop tabs, I ordered a Stage 8 kit from Summitt that turns out had aluminum tabs and liquidfied 2 of them.

Cripe. I havent had the nuts loosen up this time. I put extra effort into making sure the two hard to tighten nuts were tight and they didnt loosen up this time.

No OEM uses Inconel. It is way too expensive for production vehicles.

Inconel looks similar to stainless steel. These studs are 12.9 heat treated steel.

^incorrect, lots of nissan cars have used inconel, as stated lots of OEM turbocharged aplications, particularly those using small turbine housings relative to displacement used inconel fasteners. If they didint there would be lots of factory failures.

12.9 steel is very brittle and would do very poorly in a high temperature, heat-cycled application. It also has a very different coefficient of expansion than the cast steel it is being used to retain. See the 70 page thread where this has been beaten to death for years on this forum. Inconel is the droid you are looking for.

Define "brittle". Grade 12.9 minimum elongation requirement is 8% vs. 9% for grade 10.9. 1% difference makes it brittle?

Those are spec minimums. Actual condition is usually >12% elongation. Maybe not 30% of some low strength mild steel but hardly what I consider "brittle".

Regular 12.9 steel fasteners are not great for this application but it certainly isn't because they are "brittle".

Incorrect, they make the stud out of a material which grows at the same rate as the turbine housing as it heats up.

How can Nissan source Inconel so much cheaper than anyone else ?!

Material and machining the stuff is expensive

Inconel studs are cost prohibitive on OEM vehicles.

Inconel: https://www.miataturbo.net/attachmen...ine=1414505901

Inconel again : https://www.miataturbo.net/attachmen...ine=1414505901

This blackened, mass produced shit is not inconel: https://www.miataturbo.net/attachmen...ine=1414505901

And again: https://www.miataturbo.net/attachmen...ine=1414505901

Not inconel

A turbo vehicle warrantied for 100K miles is using appropriate high-heat fasteners in selected locations. Inconels (a family of nickel-based alloys originally developed in the 1940s) are one of the most cost-effective high-heat fasteners around when purchased in bulk.

The black in your picture is a surface treatment (black oxide). It's not the natural color of the material. The Nissan bolts discussed in the original post of this thread are an Inconel even though they have black oxide surface treatments.

Inconel alloys, in addition to high-heat strength, have Ctes extremely similar to cast iron/mild steel making them ideal turbo fasteners. Google material properties.

If you believe Nissan is selling actual Inconel studs for $5 a stud (at a profit) you are delusional my friend

Inconel does not corrode like steel and does not need a black oxide surface treatment

What then is the justification for companies that offer both natural finish and black oxide for inconel 600 safety wire? Is it just cause black looks cooler?

I may be a lot of things, but delusional is not (usually) one of them.

Black Oxide is one of many finishes that can be applied to almost any fastener, including Inconels. https://www.fastenersclearinghouse.c...5=&Cat6=&Cat7=

All metals (except Au) corrode.

i reckon they black oxide treat them cos they want to reduce they're profit margin just a little bit more after using inconel

Also I might start selling these Inconel nissan studs to FM and BEGI

I mean even if we split the profit there's about $7.50 profit each per stud

I think we should ban the term "inconel" on this forum.

There are so many grades of "inconel" with a wide variety of properties (and cost). I could do a full lab grade battery of tests on the Nissan bolts to show exactly what chemistry and grade it is, but it doesn't matter.

The costs of the various inconel grades vary wildly, probably because their chemical make ups also vary wildly. Do you think an inconel grade with 40% nickel is going to cost the same as one with 70%. What about one grade that is triple re-melted versus one that can be single melted?

Just because the Nissan bolts are cheaper and less shiny than some random pictures of inconel doesn't mean jack diddly.

I seriously doubt Nissan used the fanciest, most expensive aerospace grade of "inconel". No, I'd be willing to bet they chose one of the much lower alloyed, simpler processed grades of "inconel". I bet they chose one that would fit their needs for the lowest cost possible.

Here's what really matters though. DO THEY WORK? Do they work as turbo hardware and do they not creep like a stainless or regular steel stud would? That's all that matters. It doesn't matter if they're made from grade 718, 720 plus, Rene 65, Monel, grade 600 or rhino horns and unicorn jizz. It doesn't matter if they're coated, shiny, rainbow colored, etc etc etc.

The next time we're going to argue about "inconel" maybe we should get educated and talk about specifics and not ridiculous generics.

Also, this thread has turned to poop.


What I really want to know is this, who has used the Nissan parts (or Mazda RX-7) and had success with them?

many of us, yours truly included.

however, I have seen (and personally extracted) slightly stretched poverty inconel studs mentioned above, from a subaru before.

so maybe they're somewhere in between regular steel and balleur inconel, and maybe this isn't as cut/dry as we make it out to be, but the bottom line is your question: do they work better than regular steel studs? yes.

I think that's the most important part.

Nissan 1406440P01 studs are non magnetic, as in zero measurable attraction to a strong magnet. What does this mean?

a) They are not made from steel be it grade 8, 10, 12 etc which are all magnetic.
b) They are most likely not made from ferritic stainless steels with a relatively high concentration of iron. ie not 304, 316 etc. Lower grades of stainless are nearly always are mildly magnetic.
c) They are probably (Pauli Exclusion Principle) made from a highly austenitic stainless steel grade with a low to zero iron content and a high nickle content, something like 718 stainless.

As for color the Nissan 1406440P01 stud threads are rolled as opposed to cut and have a dull / tarnished surface as opposed to a black finish or shiny one.

So why does the aftermarket charge such a high price for 718 stainless and equivalent studs? Nickel is 7$ per lb but this does not explain the typical 25$ stud / 500$/lb price. Recently I got quotations for m8 and m10 718 studs and got offers around 5$ per piece FOB, all be it for larger quantities. Nissan for sure have better prices.

:bowrofl:

Why don't we have a poop smiley?

I have used the Nissan 14434-V0301 M8x1.25 bolts on my turbo to downpipe connection for about 20K miles including a fair amount of track time. No issues.

For the really high-heat manifold to turbo connection, I'm using TSE's 10mm studs. Again, no issues. Andrew spent a fair amount of time selecting the best Inconel alloy for the job and sized it correctly.

Does that help?

Thanks for the responses gehs. Just FYI, I knew you guys were using these studs.

The reason I asked the question was not for my benefit...

Is it possible that, like the BMWs, they are creep resistant 422 stainless steel...

Ok, I'm putting my flame suit on now & double posting. We bought a set of the Nissan 14064-40P01 studs to evaluate them. They don't look like Inconel, and they don't cost like Inconel. So, I called up my Nissan rep & asked him to contact Nissan Technical for me to find out what these studs are made of. According to Nissan Technical:

"The engineering drawing identifies this stud to be made of “AISI 660” with “bonderizing” surface treatment, which is an anti-corrosion phosphate coating. So, not Inconel, but corrosion resistant."

There you have it. If you'd like to compare this to our FM Inconel 718 hardware, ours has a minimum strength of 220 ksi. If you look up Inconel 718 it’ll tell you 180, but ours are heat treated twice.

And it looks like 660 ranges from 98ksi to 190ksi tensile strength dependent on processing. This does seem like a correct material to use for this application. Its still the best budget choice and is going to be superior to normal stainless or mild steel studs. If these are not enough for you, then you might as well go all the way to 10mm inconel studs.

Just bought another set of the 718 inconel studs from FM. Thanks guys!

I have the Nissan OE bolts for turbo to downpipe, and since 'standard' studs don't belong within a 10ft radius of a turbo manifold, I also have a set of the nissan studs for turbo->manifold back-ups in case I need a replacement just to get home. But limp-home back-ups are all they are.

-Ryan

Regular 'ole grade 12.9 bolts have ~177 ksi tensile strength.

They should be good right?

They dont have that strength at elevated temperatures like either the 660 alloy or 718 do, and the rate of expansion is wrong.

:hustler:

I remember my first time reading sarcasm on the internet...


I'm going to develop a stud kit made from maraging steel with 350 ksi tensile strength...suck on that FM with your 220 ksi 718... child's play.



Wait, nope, I'm going to develop a stud kit made from precipitation strengthened 13-8 stainless steel...that has 205 ksi tensile strength! And it's stainless! And they use it in planes and stuff! And it's cheaper than "inconel"!!!

Sooooo, Lloyd D was right, the whole time?

No, he said they were 12.9 heat treated steel.

Oh yeah, forgot that part.
Nissan looks like my choice. Thanks for the part #'s guys.

Obviously we're all aware of the issues with the manifold to turbine studs. Concerning the turbine to downpipe studs however, I'm not aware that anyone has issues with the standard A2 / 304 stainless studs we've always used. We sell a ton of kits & if it was a problem I likely would have heard about it long ago. Does anyone have pragmatic feedback on this, most likely with the track cars?

Heat load at turbine to downpipe is MUCH less. Heck, I've even gotten away with mild steel for several thousand miles at that connection. Turbine does a heck of a job extracting the heat and turning it into mechanical energy.

I had a few fail before going to a better arrangement (v-band).

Edit-wrong thread lol

We've done a little research into thermal expansion rates. Here's what we've found so far. It seems that our Inconel studs actually match the expansion rate of the cast iron best. If anyone wants to do their own research I'd be interested to hear what you find- here's a great resource.

The Garrett & ATP turbo housings we use are described as “High silicone ductile cast iron” which is a little vague, but none of the different versions on matweb.com have a thermal expansion ratio. We did find a spec elsewhere for D-5 (which is typically used for gas turbines) that gives a spec of 7.8 at 1400°F.

Material Thermal expansion (microinch/(inch°F)) at temp Tensile strength, ultimate
Cast iron, A536, 100-70-03 (our manifolds) 7.56 69.8°F - 1650°F 110 ksi
Cast Iron, A536, 120-90-02 7.61 69.8 - 1650°F >= 120 ksi
Stainless Steel A2 / 304 (standard studs) 10.4 32 - 1200°F 73.2 ksi
Inconel 718 7.2 68 - 212°F 220 ksi
Inconel 718 alternate temp 8.9 1400°F 220 ksi
AK Steel type 410 6.5 32 - 1200°F 221.2 ksi
AISI 660 / A-286 10.8 69.8 - 1650°F 174 ksi
Turbine (assuming high silicone ductile, type D-5) 7.8 1400°F