2G Turbo Hardware

[cswindel]

BLUF: Can I run bolts instead of studs to connect the turbo to the exhaust manifold? Additional question about turbo-to-downpipe hardware follows

So this "custom" 2G keeps coming with surprises. The studs that connect the turbo to the exhaust manifold are wonky and APPROXIMATELY a 3/8" diameter (actual measure is 9.25mm) and 16 SAE pitch (darn close to a 1.5 metric pitch but not quite). Flange end-to-flange end I've got about 1" total thickness (so minimum length of fastener would have to be 1"). I've looked on Fastenal and McMaster but the best I can find are some bolts to run. I suppose I could go to an auto parts store and maybe find a proper double end stud of questionable quality but my question is:

Will there be a hinderance if I run bolts instead of the studs with running the bolts from the base of the turbo flange into the exhaust manifold flange (so basically install the bolts upside-down). This is the only method of install I've got because the clearance of running them from the top of the exhaust flange into the turbo flange is way too tight. I wont be able to even fit the bolts through this route kind of tight.

Also, what would the recommended set up be for the turbo-to-downpipe hardware with the given dimensions: M8-1.25 with the lengths varying due to differences in where the holes bottom out in the turbine housing. The depth measurements with the downpipe flange thickness added to the depth measurements are: 69.37mm, 60.17mm, 32.17mm, 31.67mm, 32.23mm (again this would be MAXIMUM length the bolt could possibly be).

Would it be best to find grade 8 bolts that are close to these lengths and just run them with double washers?

Thank you all, I know this is nuts and may not make sense so please let me know what clarification is needed. Just want to make sure my turbo doesn't randomly fall out one day, you know how it goes.

 

[CanadianTalonTC]

This was a confusing post, but there was a lot to take in but it was well written.

So best I can take is that you have some sort of maybe worn down studs for your turbo you want to eliminate. Step one for me would be to remove the studs and measure the actual hole they are threaded into and I personally would just get 4 new studs cause I way prefer them for things where I cannot access one side. Alternatively you could simply get bolts that are the same dimensions as the studs and thread them in like how the factory mitsu does (just it sounds like yours are threaded to the mani rather than turbo).

However what I am gathering your idea is, is to use a bolt that is smaller than what it was before so it slips through the threads and crank it down with a nut on the other side? I am sure it will work fine, the gasket only cares about the clamping force and I highly doubt we are anywhere near the limits of some high quality bolts. Use some anti seize for sure, especially if the nuts are not accessible later for a nut breaker when they inevitably become one. Might not be a bad idea to slip a couple factory washers in there if the bolts are the right size. They do a great job of locking.

As far as the 02 housing, I would get quality bolts that are one step down from the maximum, use anti seize and a locking style washer torqued to the appropriate material and fastener size it's going into.

 

[cswindel]

This was a confusing post, but there was a lot to take in but it was well written.

So best I can take is that you have some sort of maybe worn down studs for your turbo you want to eliminate. Step one for me would be to remove the studs and measure the actual hole they are threaded into and I personally would just get 4 new studs cause I way prefer them for things where I cannot access one side. Alternatively you could simply get bolts that are the same dimensions as the studs and thread them in like how the factory mitsu does (just it sounds like yours are threaded to the mani rather than turbo).

However what I am gathering your idea is, is to use a bolt that is smaller than what it was before so it slips through the threads and crank it down with a nut on the other side? I am sure it will work fine, the gasket only cares about the clamping force and I highly doubt we are anywhere near the limits of some high quality bolts. Use some anti seize for sure, especially if the nuts are not accessible later for a nut breaker when they inevitably become one. Might not be a bad idea to slip a couple factory washers in there if the bolts are the right size. They do a great job of locking.

As far as the 02 housing, I would get quality bolts that are one step down from the maximum, use anti seize and a locking style washer torqued to the appropriate material and fastener size it's going into.

Thank you so much for this! And actually the first part of your response is spot on, except flipped. I should have clarified that the manifold flange is the one with the threads. The turbo flange is a smooth hole, so originally the janky studs were screwed into the exhaust flange and the turbo was connected via the nuts.

I'm thinking a bolt with double washers would be okay, I just don't know if I have enough room on the end of the exhaust manifold flange to fit a nut but i could try. Just worried if i dont run a nut on the end they may be more susceptible to backing out since they will be mounted upside-down (head of the bolt will be on the bottom side of the turbo flange).

I think the downpipe (o2 housing) side will be easier to navigate, especially with what you mentioned, but I'm just concerned that if I cant find a proper double thread stud that fits the dimensions ill be running a plain ole bolt and no nut on the end to help lock it in. Plan is to run grade 8 or higher spec bolts and avoid stainless ones as I dont think their thermal qualities are the best for this.

Hope this helps make sense of the situation. If pictures are needed I can roughly configure what it would look like as nothing is bolted to the engine yet.