Exhaust Stud Stripped--Help Please

[svtmatt]

The lower exhaust stud on Cyl 2 has stripped on my engine.  This is the 3rd time this has happened.  I had helicoiled it once, and the M8 helicoil failed.  Since the M8 helicoil leaves M10 threads, I installed a M10 stud directly into the hole.  That configuration has now failed.  I don't think there is enough material there to helicoil it again since I'd have to use a M10 helicoil (M12 hole).

Does anybody have any suggestions on how I can fix this short of having an expert welder fill in the hole with aluminum and starting over?

MT

[canabl]

We have some good alloy glue style silicones over here. They use it to hold the latest lotus elise chassis together. Strange that the same stud keeps stripping, may be too tight on the one side?

[VMS Motorsports]

Hillbilly dirt boy here, but I had an exhaust stud strip out in the middle of the season once. I just mixed up some JB Weld and screwed it back in. Held through the end of the season, probably 12-15 races. Was still good, just had it welded and repaired because the motor was rebuilt

[svtmatt]

Since I already had an M10 hole I was nervous about tapping it again.  I did tap it 7/16-20 and then had a machine shop take a 7/16-20 bolt, drill a hole down the very center of the bolt and then tap that hole to M8-1.25.  I coated the bolt with some high temperature exhaust repair putty (not JB weld beacuse that stuff can get soft at high temperature) and installed the bolt.  Then I cut the remainder of the bolt that was sticking out off with a dremel tool flush so the bolt is flush with the head.  Then I installed an original M8-1.25 stud in the 7/16-20 bolt. 

Hopefully this works for the rest of the season or maybe longer.  Hank Scott helped me out again with this suggestion of getting a 7/16-20 bolt, drilling/tapping it, and using it as an insert of sorts for the original M8 fastener.  Thanks to Hank!

MT

[Gimpster]

 The insert should hold no problem. Time Serts have been around for a while and would have been nice to have inserted instead but the drilled bolt should hold. Jb Weld does make a high temp version that will hold 600 psi at 400 degrees for 10 minutes and that is not when applied to threads.. it would hold more psi per heat heat when applied to threads. I believe the normal Jb is good for 500 psi. I have never had a Sert pull back out on exhaust after repair. Time Serts have the final threads cold rolled to lock the insert into place when installed so heat is really no issue. I still wipe some JB on Time Serts when installing though.
 I bring this topic back to light in case that home made insert does not hold, there is another option that will work (the Time Sert) other than aluminum welding the hole closed and re-tapping. The 8mm kit is available for around $80 with multi inserts included. I have a master kit and 24 individual Time Sert kits in my tool arsenal. Done the procedure on aluminum over mega years.
That stud should hold, don't over torque it...

~G~