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Category

      Blocks           Crankshafts          Connecting Rods         Pistons    

        Heads/Intakes          Valve-train          Head to Block Fitment

                                    Charts

         LS Gen III/IV Engines                                                   LS Camshafts

         Compatibility Heads vs. Intake                                  LS Pistons

         Compatibility Heads vs. Block                                   LS Rings

         LS Block Quick Reference Guide                              LS Push Rods

         LS Cylinder Heads                                                        LS Valves

         LS  Head Gaskets/Bolts                                               LS Valve Springs

 

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

The oiling system on every block will work with the standard wet sump or the dry sump of the LS7 or an aftermarket dry sump oiling system

 

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.

The real differences between the Gen III and Gen IV blocks are simple to recognize.  Gen III blocks have cam sensing in the top rear of the block.  Gen IV blocks rely on a sensor in the front timing cover.  Gen III blocks generally do not have AFM capability, Gen IV generally to have AFM provisions.

 

LS1/LS6

LS1 blocks were produced from 1997 through 2004 and used for LS6 engines as well.  They are cast aluminum with iron cylinder liners with a stock bore size of 3.89”.  This is a non-Siamese bore block, over-boring is limited to .030”.  The liners were designed for a stock stroke of 3.6”.  Stroker combinations should be limited to around 4.00” (piston design will determine max stroke).  They use Gen III cam sensing provisions, but Gen IV cam sensing can be used with this block through the use of a Gen IV front timing cover and blocking/plugging the rear-sensing hole.  There are no provisions for AFM.  Main bearing bulkheads are solid, and the main caps are iron.  Due to is smaller bore size, only LS1, LS6 and LS2 heads will work with this block.

 

LS2

LS2 blocks have been in use since 2005.  They are cast aluminum with iron cylinder liners and have a stock bore size of 4.00”.  This is a non-Siamese bore block, over-boring is limited to .030”.  The liners were designed for a stock stroke of 3.6”.  Stroker combinations should be limited to around 4.00” (piston design will determine max stroke).  They use Gen IV cam sensing provisions through the use of the Gen IV front timing cover, Provisions for AFM are present.  Main bearing bulkheads are solid, and the main bearing caps are iron.  Due to its slightly bigger bore size, not only do LS1, LS6 and LS2 heads fit, but L92 and LS3 heads work with this block as well.

 

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

LS7 blocks have been in use since 2005.  They are cast aluminum with iron cylinder liners with a stock bore size of 4.125”.  This is a Siamese bore block and over-boring is limited to .030”.  The liners were designed for a stock stroke of 4.00”.  Stroker combinations should be limited to around 4.12” (piston design will determine max stroke).  They use Gen IV can sensing provisions through the use of a Gen IV front timing cover.  Provisions for AFM are not present.  Due to increased engine size, increased max RPM, and to increase power output, the main bearing bulkheads a=were designed with bay-to-bay breathing windows.  The main caps are high strength, fully profiled powder metal castings and are dowel located.  Due to its larger bore size, all LS small-block heads with work with this block, including LS7 and C5R racing heads.  GMPP also offers a solid main bearing bulkhead block for enthusiasts who will be using an aftermarket dry sump oiling system or a scavenging pump system.  GM part # 25534427

 

L92/LS3/L99

L92/LS3/L99 blocks have been in production since 2007. (LS3 starting in 2008)   They are cast aluminum blocks with iron cylinder liners with a stock bore size of 4.065”.  This is a non-Siamese bore block, over boring is limited to .030”.  The liners were designed for a stock stroke of 3.6”.  Stroker combinations should be limited to around 4.00” (piston design will determine max stroke).  They use Gen IV cam sensing through the use of a Gen IV front timing cover.  Provisions for AFM are present, but only used in L99 engines.  The L92 engine incorporates advanced technology including variable valve timing.  Main bearing bulkheads are solid, and the main bearing caps are iron.  Due to its slightly larger bore size, LS1, LS6, LS2, L92 and LS3 heads will work with this block.

 

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

LSX Bowtie blocks were introduced in 2007.  They are cast from a more durable, stronger cast iron than production iron blocks.  Stock bore size is 3.99” with .010” stock for honing to 4.000”.  This is a Siamese bore block with a recommended max bore size of 4.200”.  Extra material was designed in, however, to accommodate an absolute max bore size of 4.250”.  The bore lengths were designed for maximum stroke, while still providing hone over travel clearance, which is cut at 4.28” diameter.  Stroker combinations can reach 4.25”, however rotating assembly design will be critical in stroke lengths exceeding 4.125” and heavy metal will be required for balancing the crankshaft.  LSX blocks require the use if a Gen Iv front timing cover to accommodate cam sensing.  There are no provisions for AFM.  Due to its racing design, increased engine size, increased max RPM capability, and to increase power output, the main bearing bulkheads are cast with bay-to-bay breathing windows.  The main caps are high strength billet steel, are dowel located and are secured with LS7 fasteners.  The deck height is .020” taller than stock to accommodate various engine builds.  The head bolt pattern has been upgraded from the stock 4-bolt per cylinder to include an additional 2 bolts per cylinder.  Depending on final bore size, any LS small-block head will work with this block, including LS7 and C5R racing heads.  The oiling system was redesigned to a true priority main system-oil is supplied first to the main bearings, and then to the rest of the engine.

 

Gen III & Gen IV Small Blocks
Part Number Description Liters CID HP TQ Bore Stroke
19165628 LS327/327 5.3 327 327 347 3.780" 3.622"
17801267 LS1 5.7 346 350 365 3.898" 3.622"
17801268 LS6 5.7 346 405 395 3.898" 3.622"
19156262 LQ9 6.0 364 345 380 4.000" 3.622"
19165484 LS2 6.0 364 400 400 4.000" 3.622"
17802134 LS364/440 6.0 364 440 404 4.000" 3.622"
19171224 LS376/485 6.2 376 485 475 4.065" 3.622"
19171225 LS376/515 6.2 376 515 469 4.065" 3.622"
19201992 LS3 6.2 376 430 424 4.065" 3.622"
19171821 CT525 6.2 376 525 471 4.065" 3.622"
19165058 LS7 7.0 427 505 470 4.125" 4.000"

 

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.

LSX Crankshafts
Part # Note Material Reluctor Wheel Stroke Description
19170388 8-bolt flywheel or flexplate required 4340 premium steel 58X 3.622" Reguires Balancing
19170389 8-bolt flywheel or flexplate required 4340 premium steel 58X 3.750" Reguires Balancing
19170390 8-bolt flywheel or flexplate required 4340 premium steel 58X 4.00" Reguires Balancing
19170391 8-bolt flywheel or flexplate required 4340 premium steel 58X 4.125" Reguires Balancing

 

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

The connecting rods are all very similar.  All rods except for the LS7 & LS9 are powder metal steel, whereas the LS7 & LS9 rods are titanium.  4.8L rods are 6.275” long, LS7 7.0L rods are 6.067” long, and all the rest are 6.098” long.  Starting in 2006, all rods are now made with bushed small ends (wrist pin end).  If you have a set of earlier model LS rods (pre-2000), we offer the LS6 upgrade bolts (part# 11600158) for performance use.  As mentioned before, the LS7/LS9 rods are titanium, but there are also a couple of other items of interest we should discuss.  First off, the small end of the rod is scalloped on the top half of the rod to clear the inner bracing of the piston (due to the bracing of the piston, non-LS7/LS9 rods will not work with LS7/LS9 pistons).  Additionally, the bore in the big end is a little different size than that of the other rods, necessitating a different rod bearing (part# 89017573).  The bolts in the LS7 rods are stretch to yield, and need to be replaced at each rebuild (part# 11609825 is a set of 16 bolts).

 

Pistons

All the LS pistons are very similar.  All are made of hypereutectic aluminum (except the LS9) and should not be used in applications exceeding 550HP.  The biggest difference between them all is bore size.  The 4.8L and 5.3L pistons are identical.  As mentioned in the connecting rod section, the inner bracing of the LS7 piston requires a uniquely designed LS7 rod.  Opposite to this, the LS7 rods should fit any LS piston, but doing this would require checking piston to crankshaft clearance at BDC.  LS9 pistons are forged aluminum and like the LS7 pistons, require the use of LS9 connecting rods.

 

Heads

 
Casting Number 241
Head: 1997+ LS1 5.7 Litre Passenger Car
Material: Aluminimum
Part Number:
12559853 (1997-98)
12559853 (1999-00) (not sure why same PN)
12564241 (2001-03)
Combustion Chamber Volume: 66.67cc
Compression Ratio: 10.1:1
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches


Casting Number 243
Head: 2001 LS6 5.7 Litre Passenger Car
Material: Aluminimum
Part Number:
12564243
Combustion Chamber Volume: 64.45cc
Compression Ratio: 10.5:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Casting Number 706
Head: 1999+ LR4 4.8 Litre Truck
1999+ LM4 /LM7 5.3 Litre Truck
Material: Aluminimum
Part Number:
12559852
12561706
Combustion Chamber Volume: 61.15cc
Compression Ratio: 9.5:1
Intake Port Volume: 200cc
Exhaust Port Volume: 70cc
Intake Valve Diameter: 1.89 inches
Exhaust Valve Diameter: 1.55 inches

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

 


Casting Number 373
Head: 1999-2000 LQ4 6.0 Litre Truck
Material: Cast Iron
Part Number:
12561873
Combustion Chamber Volume: 71.06cc
Compression Ratio: 9.5:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Casting Number 317
Head: 2001+ LQ4 6.0 Litre Truck
Material: Aluminimum
Part Number:
12572035
Combustion Chamber Volume: 71.06cc
Compression Ratio: 10:1
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Head: GMPP C5R
Material: Aluminimum
Part Number:
12480005
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.

Specifications, charts and Compatibility
All LS Catalog listings

 

 

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Last modified: 11/20/13.