Like all truly great war plans, Chevy's designs for the Avalanche didn't quite survive contact with reality. With its unique body and it 5.3-liter LS engine, which used superior head flow to deliver torque belying its displacement, the Avalanche seemed as unstoppable as its namesake. But, the muses of war are fickle, and fortunate were the few who wound up owning an Avalanche.
The LS engine is very little like the small-block that came before, and not many of the same rules apply. To start with, the 5.3-liter from this vintage used single-use "torque-to-yield" bolts, which permanently stretched when torqued down once. But that's not what makes TTY bolts truly brain-frying; in order to get the proper amount of stretch, they have to be torqued to a certain foot-pound reading, and then turned a certain number of degrees past that using an angle torque wrench. GM recommends part number J 36660-A. And even that's not the end of it, because the angle required for that stretch varies by the length of the bolt, and the position of that bolt; the 5.3-liter LS uses three different specifications, depending on the bolt.
Check the Resources section for a couple of bolt sequence pictures, and open them in a second window. The LS uses two different bolt sizes; the top row, nearest the intake, uses M8 bolts, and the rest are M11. The tightening procedure is as follows, in multiple passes:
Tighten all the M11 bolts to 22 foot-pounds in sequence from No. 1 to No. 10. Repeat with a second pass, turning them 90 degrees farther in sequence. On the third pass, turn bolts 1 through 8 by a further 90 degrees, and then No. 9 and 10 by 50 degrees. Finally, tighten all of the M8 bolts to 22 foot-pounds in sequence, starting at the No. 11 bolt and working back and forth to the No. 15 bolt. Be very careful; if you mess up tightening one bolt, you could wind up buying a whole new set for about $100 online.
