Head torquing
Thread Starter
Teching In
Joined: Dec 2013
Posts: 25
Likes: 1
From: San Diego
Head torquing So I ended up doing my degrees wrong on torquing. I was thinking all the way around was 180 not 360. So I ended up torquing some not all to 270deg on second pass thinking it was 90. Yep I know super stupid. Backed them out alread too! Question is, do I need to replace the bolts and head gasket on that side now? Or just the bolts?
TECH Addict
Joined: Dec 2017
Posts: 2,190
Likes: 976
Probably not, since you didn't torque them to yield.
That style of "bolt" works differently from what we were all accustomed to back in the SBC/BBC type days. Back then, a "bolt" was supposed to be an immovable clamping device, that you tightened until it clamped to the correct force, and once tightened to that point, it was never supposed to change. Problem was, things around it DID change. And when they did, the bolt was no longer clamping correctly.
TTY (torque to yield) bolts work DIFFERENTLY. Think of them as a SPRING: they're nowhere near enough "bolt" to function the same way they would have in the old days. Instead, you torque them until the tension on them exceeds their "yield" strength, by some controlled amount; and instead of "clamping", they now "yield" as the force on the increases, but retain the same tension at all times, even if the parts clearances change. They're like a REALLY TIGHT spring.
Mentally compare the way a worm-gear hose clamp works, to one of the spring type that you remove with pliers. Same principle. Worm gear, you tighten the crap out of it, but sooner or later, the rubber hose deforms, and it's loose. Spring type, it's never really "tight" as such, but no matter whether the rubber expands or contracts, it keeps the same tension.
That style of "bolt" works differently from what we were all accustomed to back in the SBC/BBC type days. Back then, a "bolt" was supposed to be an immovable clamping device, that you tightened until it clamped to the correct force, and once tightened to that point, it was never supposed to change. Problem was, things around it DID change. And when they did, the bolt was no longer clamping correctly.
TTY (torque to yield) bolts work DIFFERENTLY. Think of them as a SPRING: they're nowhere near enough "bolt" to function the same way they would have in the old days. Instead, you torque them until the tension on them exceeds their "yield" strength, by some controlled amount; and instead of "clamping", they now "yield" as the force on the increases, but retain the same tension at all times, even if the parts clearances change. They're like a REALLY TIGHT spring.
Mentally compare the way a worm-gear hose clamp works, to one of the spring type that you remove with pliers. Same principle. Worm gear, you tighten the crap out of it, but sooner or later, the rubber hose deforms, and it's loose. Spring type, it's never really "tight" as such, but no matter whether the rubber expands or contracts, it keeps the same tension.
