Note: Allpar does not take responsibility for the veracity of any information or opinions here, does not claim expertise, and is not responsible for any consequences. Please proceed at your own risk.
A bolt of the same size, thread, and material in a given grade can generally be tightened to a given torque; for example, grade-5, 1/4-20 should be torqued no more than 7 ft-lb in cast iron or 6 ft-lb in aluminum. In grade 8, those numbers are 11 and 9. This should apply universally to all such bolts, with some exceptions, e.g. for different alloys.
This information is for the bolt shaft size, not the bolt head size. Bolt and fastened material alloys change these numbers.
These numbers are for reference only; compare them to the bolt maker’s specifications for confirmation. We suggest using them as a guide when you cannot obtain the car manufacturer’s or bolt maker’s specifications.
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