Why do I only have 10 lbs of oil pressure after rebuilding my LS1?

After a rebuild, check the parts that commonly go missing or get installed wrong before blaming the pump:

• The missing gallery plug: Jeff Smith has seen this on fresh LS builds. A small (about 0.625 in) steel press-in plug sits in the front of the block, behind the timing cover, in the main oil gallery on the lower driver's side. Machine shops often remove it to clean the gallery. Without it, oil dumps straight back into the pan inside the front cover, and oil never reaches the pressure sensor. The fix: pull the balancer, water pump and front cover and press a new plug in flush. Iron and aluminum blocks use the same plug size.
• The oil cooler block-off plate: the plate that bolts to the oil pan just above the filter is often missing from used pans. Junkyard buyers take them because the GM part with a threaded tap is expensive. Without it, the engine won't hold pressure.
• Pickup O-ring: install it well oiled. Speedway warns a dry O-ring tends to tear and cause oil pressure problems.

See how to check an LS oil pickup.