Rebuilt Engine Information >> MAIN BEARING BOLT TORQUE CAUTION

Rebuilt Engine Information >> MAIN BEARING BOLT TORQUE CAUTION

Main Bearing Bolt Torque Caution For
GM High Performance Engines

The AERA Technical Committee offers the following information regarding a main bearing bolt torque caution for GM high performance engines. The information in this bulletin pertains to big and small block Chevrolet racing engines that use splayed main bearing studs and nuts. The torque value used to secure the splayed main bearing caps is not the same as other conventional big and small block engines. Main bearing housing bore distortion will result if conventional values are used.

These blocks are available in both aluminum and cast iron alloys and the torque values and procedures are unique to the alloy used. Refer to the illustrations and steps listed below to torque main bearing caps.

Use 30 weight engine oil on all studs and nuts, bottom all studs to 10 ft/lbs prior to installation. Apply FULL TORQUE nuts 1-10 before applying any torque to 11-20 (Except on Cast Iron Big Block Chevy).

Big Block Aluminum
Torque nuts 1-10 to 95 ft/lbs.
Torque nuts 11-20 to 80 ft/lbs.

Small Block Aluminum
Torque nuts 1-10 to 65 ft/lbs.
Torque nuts 11-18 to 60 ft/lbs.
Torque nuts 19-20 to 45 ft/lbs.

Cast Iron Small Block
Torque nuts 1-10 to 65 ft/lbs.
Torque nuts 11-16 to 60 ft/lbs.
Torque nuts 17-20 to 40 ft/lbs.

Cast Iron Big Block
Torque nuts 1-10 to 110 ft/lbs.
Torque nuts 11-20 to 100 ft/lbs.

The AERA Technical Committee

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