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An old timer at the Freightliner dealer in Tacoma told me I was over-torquing injector hold-down bolts
He said he could hear it in my description of the job and that I was probably stretching the threads... I was using 35 ft-lbs on a 6.7L Cummins, but he said to drop it to 28 and use a torque-angle gauge for the final quarter turn. Changed my whole approach on rebuilds. Anyone else have a torque spec that surprised them?
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uma_ellis2mo ago
That torque-angle gauge advice is solid. I've seen way too many aluminum heads get wrecked by just cranking to a number. The spec is just the start, the final turn is where the real clamp happens. Stretching those threads means you're buying a timesert kit on the next teardown. Your old timer saved you a massive headache.
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jennifer_jenkins2mo ago
Exactly. The book gives you the number, but the angle tells you the stretch. On those aluminum blocks, I always run a tap through the threads first, clean them with brake cleaner, then chase with a thread chaser. Even new bolts can bind on leftover thread locker.
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jamesf412mo ago
Disagree with that take on the torque angle. The spec is the spec for a reason, especially on those 6.7L injector bores. Going softer than factory just risks a blow-by leak down the road. That final turn isn't some magic secret, it's part of the calculated clamp load. Seen guys chase leaks for weeks because they under-torqued listening to shop talk. Stick to the book unless you have a service bulletin in your hand.
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