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.