Heli Coil failed, whats next?

[Funfettie]

Hi there,
I had a heli coil fail that was installed to repair a stripped exhaust manifold stud.

just went to torque down the studs again to 23ft lbs, and the stud pulled out
again.

The heli coil is fine, but the head is stripped again. What could i use to repair this?
Thanks

 

[3kgt2nv]

My guess is that the pilot hole for the heli coil tap was the wrong size. Or when you snapped the installation tab off you pulled the heli coil off the threads allowing it to be screwed in as you installed the bolt or stud.

Working in a machine shop we used to preemptively heli coil any threads that were in aluminum because of how easy they are to strip and we never had any issues with them restripping the threads unless they got tweeked when installing them.

 

[My1GLaser]

Double check what went wrong and check the threads that were cut for the helicoil. What stud? I know on the 1G head the two outer holes on the manifold have a lot of room. I would drill it and tap it to a larger bolt if it was one of those.

 

[Funfettie]

its the top outer most stud, next to the power steering pump. I didnt install the coil on this stud, I did one about 2 weeks back on a different stud. it was put in by the guy i bought the engine from, so i dont know if he did it wrong. Ill go pull it out and see if i can find the problem spot.

UPDATE: I was able to pull out the oil coil and run the tap through it further in and i had enough threads for hte new coil to bite in, bolted right up without an issue.

Thanks guys!
Tanner