Inconel 718 turbo stud

Under extreme use, the stainless steel studs that we usually 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.

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 Inconel 718 alloy and given a full 16 hours of heat treating. The threads are rolled for maximum strength. 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. 

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, and it's 33mm long overall. Yes, they look a little weird. But they're a perfect fit.

Sold individually. There are four studs between the turbo and the manifold, five between the turbo and the turbine outlet casting, and four between the turbine outlet casting and the downpipe. In reality, only the four between the turbo and the manifold see enough heat to be a problem.

Also available as part of a package that includes four studs and Stage 8 locking hardware.