The LS engine family is relatively new to the performance world, and because of this, there’s a lot of confusion and all around lack of knowledge of these engines and their respective components.  LS1, LS2, LS6, LS7…which parts are interchangeable, which parts are upgrades and which are down grades?  We’re going to explore and discuss the many differing aspects and compatibility of the many LS components, and valve train.  There’s a ton of good information packed in here, so if you know which parts you have interest in, you can skip ahead if you don’t have time right now to take it all in.  Otherwise, sit back and read from start to finish to learn 90% of what you’ll ever need to know about the LS small-block engine family.

Short Blocks

We are going to start off with the short block, and the foundation of every engine-the engine block.  Since its first offering in 1997 all the way to today, most of the characteristics of the small-block Gen III/IV LS engine block have remained relatively unchanged.  Every OEM block shares these distinct features:

v     6-bolt cross-drilled mains

v     Center main thrust bearing

v     9.24” deck height

v     4-bolt per cylinder head bolt pattern

v     Standard GM bell housing bolt pattern

v     4.40” bore spacing

v     .842” lift diameter lifter bores

Blocks

Although there are several minor differences between the OEM blocks, there are really only 4 major differences: casting material (Iron vs. Aluminum), cam sensing location, provision for active fuel management (AFM) and lastly the differences in bore size.

LS1/LS6

LS2

LSA

The baby brother to the LS9, this supercharged 6.2L engine is standard in the 2009 Cadillac CTS-V.  It is built with several differences when compared to the LS9, including hypereutectic pistons versus the LS9's forged pistons and a smaller, 1.9L supercharger.  The LSA also has a different charge-cooler design on top of the supercharger.  Horsepower is rated at 556.

LS9

The most powerful production engine ever from GM, the LS9 is the 6.2L supercharged and charge-cooled engine of the Corvette ZR1.  The LS9 uses the strengthened 6.2L block with stronger, roto-cast cylinder heads and a sixth-generation 2.3L Roots-type supercharger.  Like the LS7, it uses a dry-sump oiling system.  Horsepower is rated at 638.

LS7

L92/LS3/L99

C5R

C5R blocks have been produced from 2000 through 2008.  They are cast from a stronger, more durable proprietary aluminum alloy than OEM.  After casting, these blocks are treated to a “hipping” process to provide even more strength and durability.  Each block is also x-rayed to ensure there is no porosity.   They are fitted with C5R spec cylinder liners with a stock bore size of 4.117”.  This is a Siamese bore block, over-boring is limited to 4.160” max bore size.  The liners were designed for a stroke of 4.00”.  Stroker combinations should be limited to around 4.12” (piston design will determine max stroke).  These blocks have Gen III cam sensing provisions, the use of Gen IV front timing cover will accommodate Gen IV cam sensing.  There are no provisions for AFM.  Due to its racing design, increased engine size, increased max RPM, and to increase power output, the main bearing bulkheads are machined with bay-to-bay breathing windows.  The main caps are high strength billet steel, are dowel located and are secured with 4340 premium fasteners.  Due to its larger bore size, all LS heads with work with this block, including LS7 and C5R racing heads.  Premium head studs are also included.

LSX

Crankshafts

Most Gen III and IV crankshafts are nearly identical in design, all use the same rod and main journal sizes, and all use the same rear seal.  All but the LS7, LS9 and LSA are iron.  One major difference that needs to be noted is that the LS7 & LS9 crankshaft has a front snout that is approximately 1” longer than all the other cranks.  This is to accommodate the 2-stage oil pump used on the these engines.  Otherwise, there are some minor variations, and these can be found below.

All LS series engines are Balanced Internally.  They require a neutral balanced Flywheel/Flexplate and Harmonic Balancer.

4.8L

The 4.8L crankshaft is an iron crankshaft with 2.1” rod journals and 2.65” main journals.  The stroke is 3.267” and is designed to work with a connecting rod length of 6.275”.  They started out with a 24-tooth reluctor wheel and this was used through the 2007 model year in the classic 800 series trucks.  However, in 2007 starting with the 900 series full size truck, they were changed to the 58-tooth reluctor wheel.

5.3L-6.0L-6.2L

The crankshafts used in these engines are iron, with 2.1” rod journals and 2.65” main journals.  The stroke is 3.622” and is designed to work with a connecting rod length of 6.100”.  They started out with a 24-tooth reluctor wheel, but changed to a 58-tooth reluctor wheel in 2006.  Each engine has a specific part number for it’s crankshaft due to balancing differences of the piston weights.

LSX Crankshafts

The easiest way to put a forged, stroker crankshaft in your LS engine is using GMPP new LSX crankshafts, which are available in four stroke sizes up to 4.125".  They feature the standard length snout and can be used without modifications on most engines.

Special Note about crankshaft bolt patterns

All Pre-2009 crankshafts utilize a 6-bolt flywheel/flexplate bolt pattern.  Starting in 2009, the LSA utilizes an 8-bolt pattern, and the LS9 utilizes a unique 9-bolt pattern.  All LSX high performance crankshafts utilize the the 8-bolt pattern common to the LSA.

Connecting Rods

Pistons

Heads

Head: GMPP C5R
Material: Aluminimum
Part Number:
12480025
Combustion Chamber Volume: 38cc
Compression Ratio:
Intake Port Volume:
Exhaust Port Volume: 70cc

Head: GMPP C5R
Material: Aluminimum
Part Number:
12480090
Combustion Chamber Volume: <30cc
Compression Ratio:
Intake Port Volume:
Exhaust Port Volume: 70cc

Valvetrain

LS Series valvetrain systems are very universal.  All production engines use investment-cast rockers with roller trunnions.  They attach to a bolt-down mounting bracket (except for LS7 and LS9 applications that have machined pedestals) that makes installation fast and easy.  All production engines feature 1.7-ratio rockers, except the (LS7, which uses 1.8-ratio rockers).  Rockers are specific to their cylinder head families.  Here's a look at the various applications:

Cathedral-port heads

Use interchangeable rockers on the intake and exhaust sides, P/N 10214664.

L92, LS3 & LS9

Use specific, offset intake rockers P/N 12579615 and non-offset exhaust rockers P/N 10214664.

LS7

Use specific, offset intake rockers P/N 12579615 and non-offset exhaust rockers P/N 12579617

LSX-CT and LSX-DR

LSX-CT and LSX-DR heads require racing-style shaft mount rocker systems.  GMPP offers a 1.85:1-ratio rocker arm kit P/N 19201808 which includes all necessary hardware.

Head to Block Fitment

Because of their comparatively small bores - 3.89"-LS1 and LS engines can only use LS1, LS6 and LS2 heads.  Using heads designed for larger engines will cause valve-to-block interference.  The larger, 4.00-inch bore of the LS2 enables it to use LS1/LS6 heads, as well as L92-style heads (including LS3, LS9 and LSA).  The 6.2L engines (LS3, L92, etc) can use all production heads except for the LS7, while the 7.0L LS7 and C5R blocks can use any LS Series head.  LS7 blocks should be matched with heads designed for at least 4.10" bores; 4.125" bores are preferred.

Most LS production cylinder blocks share the same cylinder head bolt pattern and the same size head bolts-four 11mm bolts per cylinder (10 in total) and five upper, 8mm bolts.  Early LS1 and LS6 engines used different length 11mm bolts, but engines from 2004 and later use the same length bolts.  LS9 engines use stronger, 12mm head bolts.

Non-production blocks, such as the LSX and C5R, offer the same head bolt pattern as production blocks.  All LS heads will bolt up to them, but care must be taken to select the most compatible heads based on the appropriate bore size.  Because of their large bores, heads designed for at least 4.10" bores should be used and a 4.125" bore are preferred, such as the L92/LS3 or LS7 heads otherwise, calve-to-block interference is an issue, as is sufficient cylinder sealing.

GM Performance Parts new LSX cylinder heads use (10) 11mm and (13) 8mm head bolts, or eight more than a regular-production LS head.  That's more than 50-percent more head bolts than production heads, offering a 21-percent increase in total clamping capability and 100-percent more clamping in the 12 o'clock and 6 o'clock positions, right where gaskets leak and blow out in power adder applications.