Found a cracked head on a 6.7 Cummins that had been helicoiled 3 times before

I pulled this engine apart last Tuesday in Fresno and found 3 helicoils stacked in one cylinder head bolt hole from previous rebuilds. Has anyone else seen hack repairs like this holding up surprisingly well?

2 comments

2 Comments

zara_hill462d ago

Told the guy who had our shop truck to just torque it to spec and send it" - that's exactly the kind of cowboy stuff that makes me wonder if these engines are tougher than we give them credit for. Nobody's talking about how the helicoils themselves can actually act like a thread locker over time if they're installed right, especially with the heat cycles in a diesel. I've seen a few 5.9s with helicoils that outlasted the rest of the block because the stainless steel doesn't fatigue like the aluminum does. But three in one hole though... that's more about luck than engineering at that point. The real question is whether the bolt was bottoming out or if the threads were just that chewed up from previous overtorquing. Wouldn't trust that on a high horsepower build, but for a stock truck it'll probably run another 100k miles just fine.

veramiller2d ago

Told the guy who had our shop truck to just torque it to spec and send it, and it held fine for another 80k miles before we sold it.