This is from the December 09 issue of Chevy High Performance.

LS4: The oddball of the LS family, the Gen IV LS4 was designed specifically for transverse mounting in front-wheel-drive impalas and monte carlos. To accomplish this, GM shortened the LS4's overall length - from crankshaft to flexplate - by 13mm and streamlined the accessory drive. Furthermore, it shares the same 3.780 x 3.622-inch bore and stroke dimensions as Vortec 5300 truck motors, but is based on an aluminum block and topped with LS6 cylinder heads. Despite their displacement handicap, LS4's are relatively stout for their size, producing between 290-303 hp. However, they're almost as expensive as LS1's and LS6's on the secondhand market, so it's of little value to muscle car buffs seeking a swap candidate.

DISPLACEMENT: 325 ci
BLOCK: Cast aluminum
HEADS: Aluminum 15 degree cathedral port
BORE/STROKE: 3.780 x 3.622
COMPRESSION: 10:1
OUTPUT: 290-303 hp and 325 lb-ft
WHAT ITS IN: 06-09 Impala SS, 06-07 Monte Carlo SS, 05-08 Grand Prix GXP, 08 LaCrosse Super

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HID's(8000K Dims),K&N Air Charger,LED tailights,STB's F&R with Don's brackets,Custom Catback.

Mmmhm Intresting...If I am not mistaken the LS4 died with the Impala SS as of this year. Correct me if I am wrong but that is what I had heard.

From chevy's website you stand correct as of the 2010 lineup of impalas trim levels are LS LT and LTZ. Corrected first post for the drop in the Impala SS for the 2010 model year.

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HID's(8000K Dims),K&N Air Charger,LED tailights,STB's F&R with Don's brackets,Custom Catback.

I was unaware that LS6 heads were fitted. Though, I did know that the displacement (bore x stroke) was shared with the truck engines.

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One Big Ass Mistake America

I did not know the Lacrosse Super came w/ the LS4...........that's very interesting. I've only ever seen 2 of them in person...and I absolutely love how they looked. Now that I know whats under the hood of them..... i kinda want one

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-2000 Grand Prix GTP 13.341 @ 102.62
-2003 Grand Prix GT (daily driver)
1991 Grand Prix GTP Getrag 284 5 speed 1 of 787 5 speeds in 91. 15.221 @ 92.46

I was surprised when I read that the LS4 was actually lighter than the L67...not a bad trade off for 303/325

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2004 Bonneville SLE "Bonnie the Ghosthawk"
2001 GP GT coupe (now my sons)
GPONA Mopar owners club
2008 Chrysler Sebring convertible

Yep L67's block is Cast Iron. LS4's block is aluminum. Gotta love it

No doubt...I do love my GP, but the more I look at these cars the more its gettin under my skin (the wife is gonna shoot me)

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2004 Bonneville SLE "Bonnie the Ghosthawk"
2001 GP GT coupe (now my sons)
GPONA Mopar owners club
2008 Chrysler Sebring convertible