So I'm torqueing down new rockers using the GM procedure, and one rocker feels like there's no preload. The other rockers have more resistance for the last turn (actually about 1 1/4 turns) like I'd expect, until the preload is taken up, but one rocker bolt just turns easily all the way like there's no preload. So my valvetrain newbie question is: is the extra resistance during the final turn from the springs in the lifters? Or from the oil still in the lifters? Is this one lifter bad, or just has no oil (car's been sitting about 2 weeks), or should I not worry about it?

This is stock original ls1 heads, on the car, low mileage. Stock pushrods all seemed straight. Do not want to remove the heads, it's 108 degrees here. Springs are also new (ls6). Comp rockers are the non-adjustable type.

 

The lifter in question may have leaked down, which would give you the effect you're describing. It should pump up after the engine is started, however it may take a few minutes or so. If it's still tapping after 15 minutes, shut the engine down and let it sit for about 30 minutes and retry. Lifters do sometimes collapse while adjusting them. It shouldn't be cause for alarm.

 

I agree. When I did my clutch, I had to turn the motor over by hand a number of times to tighten the bolts in sequence through the access cover. I pushed all the oil out of the lifters (didn't realize at the time), scared the crap out of me when I started in the garage due to the racket the lifters made. After a few minutes they pumped back up.

Just don't rev the motor upon first start, let it start and idle until it quiets down.