gtxrt
Well-Known Member
after torque down i will wait as many days as I can and check torque again without breaking the bolts loose.
440 Head Gasket Advice
- Thread starter moparmark440
- Start date
Since torque is a measure of friction this doesn't do much for you. Friction is not what keeps the fastener tight. It's the fastener being stretched. Once the fastener has stopped rotating it will take a greater torque reading to rotate it. Example; The spec is 80lb/ft. The fastener on the first pass had enough friction to read 80lb/ft on the wrench. The actual fastener stretch can and commonly is not enough at this point. Appling torque without loosening the fasner? The wrench still reads 80lb/ft. It will most likely take over 80lb/ft to rotate it. However if the fastener was loosened and retorqued the fastener now rotates further. Why? The friction has been lessened and now when the reading is 80lb/ft the fastener is properly stretched. This is why rod bolt stretch is measured in high end builds. The actual torque is not important. It's how far the fastener stretches. Obviously in a blind hole this measurement can not be taken. This is also why the recomended lube and clean threads are critical. The wrong lube can result in not enough or to much stretch. Hope this makes it clearer.
Doug
gtxrt
Well-Known Member
i was thinking more in the lines of the composite head gasket compressing.
What started this process with head gaskets was 30 years ago. We had a 340 that during a leak down check we could see bubles in the valley (intake had been removed). It had been decked, and heads resurfaced. Composite Fel Pro gaskets. This was back when we did them like you. Just rechecked after setting without loosening. Dave gave me the tip. That fixed it. I do use the just tighten it method when torquing trans pans, oil pans, etc. They definately compress.
Doug
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