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Stage 8 hardware with Inconel studs

Stage 8 hardware with Inconel studs

Regular price $129.00 USD
Regular price Sale price $129.00 USD
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Our exclusive Inconel 718 studs combined with slip-proof Stage 8 fasteners. The studs will deal with the heat produced by hard turbo use, and the fasteners will ensure it's impossible for the nuts to back off.

Under extreme use, the stainless steel studs that we used to use in our turbo kits can expand enough to loosen off and eventually break. So we did the same thing NASA did for the X15 rocket plane, and went to Inconel. Space-age! Keith promised not to write anything else about the X15, which is good for you because he starts babbling about it every time you mention Inconel. Inconel 718 is an extremely strong material (with nearly double the tensile and yield strengths as 316 stainless steel), but it's also a much closer match for the thermal expansion of our (and most other) cast iron manifolds. Meaning that not only is the stud much stronger than stainless, but it will also be much less stressed, as the differing thermal expansion rates won't be trying to tear things apart, like with stainless steel studs. 

These M8x1.25 studs are made exclusively for FM by ARP and are a straight replacement for the originals. No drilling or retapping required. They're made of the Inconel 718 alloy and given a full 16 hours of heat treating. The threads are rolled for maximum strength.

You might notice they look a bit different than most studs. There's a reason for that - they're not a generic stud, but one that was made specifically for this application. The shoulder (the unthreaded portion in the middle) is an exact match to the depth of the flange on a turbo, so the turbo is not riding on a threaded portion. We also made both threaded portions 12mm long for more thread engagement in the manifold. Yes, they look a little weird. But they're a perfect fit.

The Stage 8 locking nuts are a brilliant design. Tighten up the nut as usual, then slip the locking tab over top and use the C-clip to hold it. Voila, a nut that cannot possibly loosen. If you need to remove it, pop the clip off and remove the tab. Simple and effective. We recommend this hardware on the turbo-to-manifold studs for any Miata that sees track use. Available as an option on our turbo kits.


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What does it fit?


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1 year



Customer Reviews

Based on 5 reviews
marlowe e.

Hey great product perfect to keep my turbo Miata together on the track . My order got damaged and missed a few items. Flyin Miata were very helpful in the customer service department. Sent replacements and came quickly!

Pricey, but then again it works

I bought this to replace old rusty standard hardware while doing an engine swap on my turbo charged 1991 Miata. After watching a prominent Miata owning YouTube personality praise a Fab9 version of this kit, I took a look at the FM one and decided to pull the trigger. It seems a bit pricey for some studs but it’s the same material used in the exhaust of the famous McLaren F1 and now I don’t have to worry about any loosening on my turbo flange. I don’t have any long term experience right now but it’s a time proven piece of kit from others.

Owen N.
Don't buy anything else if you plan to drive hard

Buy these. Don't use anything else. Why? Well I used a "strengthened" stainless arp turbo stud kit that seemed great...until my first track event where they stretched/melted slightly after 2, 20 min sessions (running a small Garrett 2522 turbo on my 1.6. Nothing crazy). Ordered these the next day, installed as per instructions when they arrived, & promptly took the car out for 2 days of abuse at Midohio. Car never skipped a beat. No stretching, no melting, no loose turbo. I should've listened to everyone (including FM) when they say "go inconel". It's pricey but believe me, they're so worth it & you will avoid a track day ended early due to a loose turbo

Tuning b.Y.
Best studs, designed specific for this use!

Having debated for many days on if this upgrade was worth it. I am happy to say it has exceeded my expectations. Packaging is wonderful as always, the studs fit perfectly with my Flyin' Miata manifold. I couldn't be happier!

A simple but brilliant solution.

The teardrop shaped washer is meant to interfere with the surrounding housing so the nut can at worst back out a quarter turn. Years of autocross abuse with 300HP and no problems. Expensive, but they work.