.0008"-.00025" seems like a very large margin for bearing clearances? why do they have such a large margin? do they get their number from trial and error? .0008" is ok but .0007" spins bearings, im mean for real where do these numbers come from? and if the motor runs better with clearances from .0019"-.0025" then why don't they just make those the recommended specs.

 

they have a wide tolerance so that they can run looser spec on all the associated parts. the tighter the spec, the more perfect every part has to be. in a stock application everything is +/-x so if all the components ended up towards the + or - side of a spec on the same engine they can still use them...

 

so if i were to start pulling apart brand spanking new LS motors I would find some motors with bearing clearances of .0009" and other motors with bearing clearances of .0022"? If thats the case it seems like the guy who got the .0009" bearing clearance motor got fucked and is way more way more likely to spin a bearing.

 

these engines are mass produced,not hand built. gm powertrain obviously felt that they can achieve good durability with those clearances.

 

Some LS motors are hand built

 

All LS engine are hand built....The difference is the time invested in such


As for the OP, like the others said, its a production engine. There are clearences outside of spec on the high end and the low end. The middle is the "acceptable" or good enough spec. Thats what the 32,000 miles warrently is for lol...Those engines that are on the border line of acceptable if they do happen to fail are covered. The "extra" time to get it precise is wasteful and cost GM money.

 

This is why new engine programs cost billions of dollars. I am sure over the years GM Powertrain has a pretty good idea of what will work. However, I am sure they destroyed hundreds if not thousands of motors developing the LS series. To tigh - failure, to loose - failure.

 

haha sorry i should be more specific when i say hand built. but for the most part, excluding limited product like the ls7, not as much care is given compared to an engine assembled by us in the aftermarket

 

I think it comes down to $. Tighter tolerances = higher part costs. You loosen tolerances as much as the engineering analysis and part testing proves that you can while still meeting life and you'll end up with a less expensive engine.