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Overheard a kid at the parts counter say 'just torque it to spec' and it got me thinking
I was picking up a gasket set for a 5.9 Cummins at the Freightliner dealer in Boise last Tuesday, and this young apprentice is on the phone telling someone to just torque it to spec. I laughed because my first mentor back in 2009 always said specs are a starting point, not the law, especially on old heads with warped surfaces. But then I started wondering if I've been too loose with that mindset, chasing feel instead of numbers. How do you guys decide when to trust the book torque over a couple extra ft-lbs on a high-hour block?
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ivan_murphy801mo ago
Specs are definitely a starting point, but that kid might have a point on the phone. I had a 12-valve head once where the book said 105 ft-lbs and the block was so tired it pulled the threads out at 90 on the third corner. After that I started checking studs and deck surface first, then I go by feel. But I also had a guy on a 466 who ignored the book and snapped a bolt clean off because the hole had old oil in it. Torque spec only works if everything else is true, which on high-hour stuff it never is. That apprentice will learn the hard way, just like we all did.
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drew_jones311mo ago
That apprentice is gonna be fine honestly. Torque to spec is the right thing to tell someone on the phone when you can't see the parts. My approach on high hour blocks has always been to hit the book number, then do one more pass with a slightly higher setting on the critical bolts only if the threads and surfaces checked out clean. Had a 7.3 head gasket job where the block was so pitted I had to drop the spec by 10 ft-lbs on a few corners just to get them to bite without stripping. That worked way better than forcing it. The real trick is knowing when the book is wrong before you start, not after.
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