Originally Posted by SilverTurtle
almost completely correct.
the LS1 vs. LS6 block is a debate that will live forever, but here are the facts:
1. the LS6 block has vents at the bottom of the cylinders to allow for better backpressure dissipation... the LS1 block did not have this.
2. the LS6 blocks that wound up in the f-bodies were made from the denser casting, and therefore were more prone to tolerate nitrous... the LS1 blocks were almost equally tolerant of nitrous, but were made from a less dense product run.
3. the way to tell if your block is an LS6 block is to look at the casting number at the top, back of the block and on the driver's side... the LS6 casting number is 12561168... anything else is the LS1 casting number.
4. LS6 heads were only available on f-bodies through aftermarket companies like GMMG built cars.
5. LS6 block f-bodies tend to have a better time at high RPMs than LS1 block engines do... we have one of each in a 2001 and 2002 Z28... I've driven both when they were stock and there really is a difference.
dont believe everything you read on LS1Tech... a site with that many people is bound to have a bunch of trolls on it that post stuff that they've heard to be true and then it spreads like wildfire.
oh, and there is rumor that the cylinder vents were added to the LS1 casting during the 2001 model run... having never seen one of these engines with one, and having seen several 2002 LS1 engines without them, I cannot confirm or deny this rumor... but this was originally stated by a GM employee who should know the facts... my only guess is that the LS1s that I ran across in 2002 cars were leftover blocks that wound up in the 2002 model cars... and probably have an incorrect date stamp to match up to the 2002 f-body.
^^^^^^^Theres a guy that knows his engines. But since everyone is getting so technical....the one thing that you forgot is
the ls6 aluminum blocks are more desirable because they are designed to handle high rpm, big hp situations. for the most part they are identical to the 01 and later LS1 blocks. LS1 blocks have a hole machined through the main webs to improve bay to bay crankcase breathing the hole cures the bay to bay oil vapor pumping issues. LS6 blocks are an improvement on that fix, so they are most desireable. they come with an open oil passage area designed in the block