Engine studs

[SimonNicholson]

Has anyone had any issues with exhaust studs pulling out of the head?

I had to do a helicoil repair on cylinder 6 and cylinder 3 exhaust studs.

[Mark Goldberg]

I think I did one helicoil repair like that 30+ years ago on an engine. It was on a J3 Cub I believe. I want to say I took the case to a machine shop. But that has been a long time. Mark

[JoHo]

The picture is showing an installed insert with the tang still on, just in case you are about to leave it there.... The tang at the end of the helicoil is intended to be broken off and discarded so the screw can go through and it doesn't become a FOD issue later.

I always design screws to thread go all the way through the insert because the way the helicoil ends up so much stronger than a plain thread is that it equalizes the load over it's entire length.

[SimonNicholson]

All the tabs were broken off before stud insertion.

[Steve W]

Unless those are high time cylinders, I’d be looking for the source of vibration that is causing that kind of destruction unless it’s a used engine that has been installed Just sayin.

[svyolo]

Not airplane specific, but at 15 to 20 years I expect to have to chase threads with a tap when removing and installing steel fasteners in an aluminum block. At 30 years doing helicoils isn't the norm, but not unexpected. Some engines are a lot worse than others and some cylinder head bolts are considered single use, and you heli-coil them by convention. I am not experienced across many car brands. Just a few.