Magazine for the auto service professional
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Circle 121 on Reader Service Card Technical If using OE bolts and following OE tighten- ing specs, use the lube specifed by the OE (which will commonly call for engine oil). If you are using aftermarket bolts, follow the recommendation of the bolt maker. Some aftermarket bolt makers may give you a choice between oil or moly, with torque values appropriate for each. Certain moly-type lubes provide greatly reduced friction as compared to oil, a torque value with moly will commonly be lower than the value recommended when using oil. Follow the bolt tightening procedure specifed by either the OE or the aftermarket head bolt manufacturer, which may specify a torque value or a torque-plus-angle method. If torque-plus-angle is specifed, you can apply initial torque with a calibrated torque wrench. You can follow this with additional angle- turning by applying a paint dot on the bolt head and visually monitoring (and guessing) the number of degrees of added rotation. Or a much easier and quicker method is to invest in an electronic torque wrench that also ofers angle tightening (enter torque mode, apply torque; enter angle mode and apply angle). ■ If a gasket leaks, there is always a root cause. If replacing a bolt, always verify bolt shank length. If thread engagement is insufcient, clamping force can be compromised. If the bolt is too long, it may bottom-out in a blind hole, preventing gasket sealing. Either problem can result in leakage.