Downpipe Fastner Question
 

My downpipe is currently connected to my turbine using (5) 20mm stainless (A2-70) bolts. I would like to replace them with ARP stainless 12 sided 25mm bolts in order to make installation easier and so that I have more threads engaged.

However, over time the receiving threads in the turbine housing have become slightly deformed such that I can only screw the ARP bolt in a little (1-2 threads), and the existing bolt only up to it's normal point of engagement (~10mm). I have chased the threads with a thread restorer, and they are not damaged. The bolts have identical threads, so no problems there.

Questions/Options:
1. Is the ARP stainless hardware appropriate for this application?
2. Since I'm not having any problems, should I just leave well enough alone and suck it up? (It's a real PITA getting the six sided bolt bolts tight with an open ended wrench)
3. Or, should I run a tap through the housing threads and install the ARP bolts?
4. Or, "You fool, there's a better solution!"

Thanks!

I dont know if they're the right bolts or not. APR could answer question 1 if you called them tomorrow. And if they say its good, I would chase the threads with a tap and run it in with anti-seize.

I exchanged emails with ARP and they felt that they would be okay. I'd be interested to know if anyone has used them in the real world.

I know that some inco studs would be best, but that would make disassembly more cumbersome.

Thank you for the feedback.

If the arp's are better in every way (sounds like they are) i'd just properly tap the housing and use em. after the turbine there isn't nearly as much heat and pressure as before, so inco isn't as drastically mandatory IMO