On the thread of little engine-building details for the LS-series engines, there is an oil diverter valve in the main oil galley at the front of the engine that is usually removed when the block is cleaned or hot-tanked. It’s easy to lose this little rascal, and the engine won’t make oil pressure without it. All LS-series engines require this valve, often called a barbell because it looks like a miniature plastic version of what weight lifters play with. If you are building an LS-series engine with a brand-new block, there are actually several small pieces, plugs, and other little gems that you’ll need to complete the assembly. GM Performance Parts sells a block completion kit (PN 19153789, GM list is $348.57 but you should be able to find it for a little less). This kit comes with sensors, front, rear, and valley covers, lifter guides as well as all the parts you’ll need to complete the block. Scoggin-Dickey (sdparts.com) has a much less expensive kit that is just the little dowels and plugs (PN SDLSPK - $74.95). I’ve listed all the individual part numbers in the GMPP kit here, so if you only need one specific part—like the barbell—you can find it here. The water and oil plugs vary with each application and are included in this kit.
Components PN
Valley cover (LS6 style) 12577927
Cam sensor (LS1) 12561211
Crank sensor (LS1) 12560228
Front cover with aeal 12561243
Trans alignment dowels (2) 1453658
Cam retainer plate 12589016
Cam retainer bolts (4) 11561455
Timing chain damper 12588670
Lifter retainer (4) 12551162
Lifter retainer bolts (4) 12551163
Rear cover with seal 12615666
Cylinder head dowel (4) 12570326
Oil diverter plug (barbell) 12618054
Oil and water plugs, (3) 11588949