I just got my GMHTP mag in and there's an article on page 11 that says some of the camaro and firebird/transam guys may be running around with an ls6 block.
In 98 GM used two providers for the ls1 block. Montupet in Canada and Nemak in Mexico. Montupet uses gravity-feed process and uses a combo of metallic dies and sand cores. Nemak uses low-pressure fan process, which is more of a hi performance process.
Then in 01 GM needed to redesign the ls1 to be a stronger ls6. Since Nemak's materials are stronger they went with them.
But still had Montupet provide ls1 blocks.
During the redesign so many were made that GM allowed some blocks to spill over into f-bodies. It is said that 10-15 percent of all 2001 f-cars and around 25percent of 02 f-cars are running around with ls6 blocks.
To confirm: look behind the drivers-side and see if you can see the back of the left-hand deck, above the transmission flange.
A cast-in 12561168 denotes the LS6 block.
A harder way to tell is, the Montuupet plant cast is shinier, the Nemak plant made duller, stronger block castings. I know that's hard to tell, but it's what the magazine says.
Starting in 03 all ls1/ls6 blocks will be of this newer Nemak configuration.
BTW, the ls6 block ventilates 87% more than the ls1, which is less pumping loss at high rpm. No official hp claims have been made, but it does increase hp.
later,
allen
(ls6 block )
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should be here friday, maybe have pics over the weekend
