Engine - Block Components - Four-Bolt Main Bearing Cap

From GM Performance - This heavy-duty iron four-bolt cap is used on bearings 1,2,3,4. Technical Notes: The ends of this semi-finished cap must be machined to register the cap in the block. Align bore the main bearing housings after installing replacement heavy-duty bearing caps.

From GM Performance - This billet steel bearing cap is used on the #2 main bearing in a Bow Tie aluminum V6/60 degree block. Its outer bolt holes angle outward toward the oil pan rails. This splayed bolt design improves reliability in highly stressed racing engines by tying the cap to the strongest part of the block. It also reduces distortion of the main bearing bores by increasing the cap's resistance to closing up under high loads. Technical Note: For 67mm diameter main bearings.

From GM Performance - Same as above, for #3 main bearing.