Gen III LS reference

Block specifications

Use this page to narrow the exact Gen III LS 4.8, 5.3, or 6.0 block before choosing rebuild, cam, upgrade, or performance parts.

Gen III engine ID guide

Displacement	Code / model	Common years	Block	Bore x stroke	Parts-fit notes
4.8L	LR4	1999-2006	Iron	3.78 in x 3.267 in	Shares bore size with many 5.3 engines. Confirm crank/rods before ordering rotating assembly parts.
5.3L	LM7	1999-2007	Iron	3.78 in x 3.622 in	Most common 5.3 truck engine. Early and late cam bearing housing bores can differ.
5.3L	L59	2002-2007	Iron	3.78 in x 3.622 in	Flex-fuel 5.3 family. Treat block parts like LM7 after confirming year and casting.
5.3L	LM4	2003-2004	Aluminum	3.78 in x 3.622 in	Aluminum 5.3 applications exist. Confirm material and casting before ordering block-specific parts.
5.3L	L33	2005-2007	Aluminum	3.78 in x 3.622 in	High-output 5.3 family. Confirm cam bearings, heads, and rotating assembly before choosing kit parts.
6.0L	LQ4	1999-2007	Iron	4.00 in x 3.622 in	Early and late versions matter. 2003 can be a split year for cam bearing housing bore.
6.0L	LQ9	2002-2007	Iron	4.00 in x 3.622 in	Higher-compression 6.0 family. Confirm year and cam bearing design before buying cam bearings.

Design	Common range	Cam housing bore 1 / 5	Cam housing bore 2 / 4	Cam housing bore 3	Buyer warning
1st design	1999-2003	2.326 in	2.317 in	2.307 in	Usually uses early Gen III LS cam bearing sets. 2003 should be verified before ordering.
2nd design	2003-2007	2.346 in	2.326 in	2.307 in	Later housing bores are larger at positions 1/5 and 2/4. Wrong bearings can ruin the build fast.

Step 01

Look near the rear bellhousing area of the block. A clear photo helps prevent ordering the wrong kit.

Step 02

Cam bearing bore, wrist pin style, and head bolt length can change around the 2003-2005 range.

Step 03

Once the engine family and block details are confirmed, choose Upgrade, Rebuild, Cam Kit, or Performance.