GM 12 Bolt Car Aluminum Main Caps
Machining Required


Part Number: H1121

GM 12 Bolt Passenger Car Housings

Will Not Fit Truck Housings

Replaces thin cast iron main caps
Cast iron caps can flex, crack, & break

Billet aluminum is much more ductile
Increased flexibility make it much less prone to breakage
Thicker material further increases overall strength

Aluminum Caps
• 2024-T351 billet aluminum
• Strong & lightweight
• Material is easy to machine
• Clear anodized
• Designed & machined by Strange
• Aluminum made in USA

SHCS Cap Bolts
• Ensures secure cap retention
• 7/16″-14 x 2.50″ to suit casting & cap height

Installation Procedure
Install caps in housing
Check and record bore sizes
Compare to included chart
Mark each cap with amount to be removed
Mill required material from the feet of each cap
Reinstall and torque to specifications

Installation kit – R5211
Chrome cover – R5199
LPW aluminum cover – R5206 / R5207


GM 12 blt. alum. main caps with bolts- pr. (requires machining)

Parts List and Installation Guide pdf File