LS Iron Block Truck / SUV Engine Guide

WWHILE most people are familiar with the high performance variants of the LS engine family tree, there are almost 40 different engines all of which hang out under the broader LS moniker. There are differences in drive configuration, bore sizing, iron / alloy construction, cylinder head port shape, lubrication, fuel and ignition systems, and much more.

This article first appeared in Street Machine LSX Tuner review n ° 9, 2019

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Street machines latched onto the iron-block LS variants thanks to the growing popularity of Stock Bottom-End (SBE) and Sloppy Mechanics builds, where iron-block LS V8s were discovered to adopt turbocharging and ethanol fuels like ducks for water. We’ve seen over 1,500bhp on a stock iron 6.0-liter rotary assembly, with cars operating in all seven overseas using cam-busting engines.

The iron blocks weigh approximately 50 kg more than the passenger aluminum LS blocks, but can be drilled further. Part of the appeal of these engines is that the internal components of the larger capacity cars match the engines of the trucks.

While 6.0L truck engines are considered the most desirable for high horsepower, GM has also made 4.8L and 5.3L engines, which helps ensure that your turbo V8 is able to exceed technical requirements.

But how do you distinguish your LM7 from your LQ4? We have the lean on the LS “truck” family tree below, divided by bore size and engine generation.

ls block

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One of the reasons LS iron blocks are so popular is their incredible availability. General Motors has made millions of pickups, vans, and trucks that they’ve jammed these engines into, which means you’re literally going to stumble upon iron LS engines in American landfills. The huge supply affects the cost of the motors and means they are usually offered at an absolute bargain price

GEN III
3.78in BORE
LR4

Also known as the Vortec 4800, this is an iron truck engine designed to replace the 305 cubic 5000 L30. It is the smallest Gen III truck / SUV engine and produced 255 hp (190 kW) for the 1999-2000 edition, 270 hp (201 kW) from 2001-04 and 285 hp (213 kW) from 2005- 06. It is found in the 1999-2006 Chevy Tahoe / GMC Yukon, Silverado / Sierra and Express / Savana models.

LM4 / LM7 / L33 / L59

The Vortec 5300 engine went through several variations during its life, known as LM4, LM7, L33 and L59. The stroke is 9mm compared to the Vortec 4800 and as of this point there are many differences. The L33 is also known as the Vortec 5300 HO. This is an aluminum block variant of the LM7 iron with flat top pistons of the 4.8L LR4, larger lift cam, higher compression ratio and LS6 cylinder heads, developing 310 hp. (235 kW). The # 799 cylinder heads would be the same casting as the # 243 LS6 and LS2 cylinder heads, minus the hollow exhaust valves and high performance valve springs. The LM4 is another aluminum block variant of the LM7, developing 290 hp (216 kW) and is not as capable as the L33. It was used in the Chevrolet SSR, the GMC Envoy, and other lightweight models. The L59 is the flex-fuel version of the LM7 found in the Avalanches, Silverados, Sierras, Yukons, Tahoes and Escalades 1999-2007. It produced 270 hp (201 kW) in 1999, 285 hp (213 kW) in 2000-03 and 295 hp (220 kW) in 2004-07.

ls motors

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You can identify the 4.8s and 5.3s as opposed to other LS iron blocks by the 4.8 / 5.3 casting mark on the front of the block. There is no other easy way to identify if you are looking at a 4.8 or a 5.3 short to shoot a cylinder head and measure the stroke.

4 inch BORE BLOCKS
LQ4 / LQ9

The Vortec 6000 came in two specifications, with the LQ4 doing 300hp to 360hp (220-268kW) and the LQ9 doing 345hp (257kW). The LQ4 is found in the GMC Yukon and Sierra, Hummer H2 and Chevy Suburban, Silverado and Express. The LQ9 is the high-output version of the LQ4, originally designed for Cadillac Escalade models. It has flat top pistons to increase the compression ratio to 10: 1. It was also used in the Silverado SS and Denali models. These engines are very popular as deep breathing LS3 style heads can be fitted for loose turbocharged power.

6.0 liter LQ4 block

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Above: This 6.0 liter LQ4 iron block was picked from a South Carolina landfill for less than US $ 1,000. Featuring a 9.4: 1 compression ratio, it is a Gen III engine and a 24 tooth reluctance wheel. While the exterior is so filled with dirt that it appears to have been used as a bulldozer at one point, the interior is in good condition. In 1999-2000, the LQ4s shipped with # 373 or # 873 heads which had 71cc chambers, cathedral ports, and 200cc intake channels with oval exhaust ports. From 2001 to 2007, the LQ4s were fitted with a cathedral orifice, 210cc intake, # 317 or # 035 heads that had D-shaped exhaust ports.

GEN IV

In 2005, after eight years, the Gen III gave way to the heavily revised small block Gen IV series. Rather than radically rethinking the platform, Chevrolet evolved the base architecture to push displacement up to 7011 cm (427 cubic inches), while also including new technologies such as electric butterflies, engine displacement to demand and variable valve timing. .

BORE BLOCKS 3.78in
LY6

The LY6 is a 6.0-liter Vortec Gen IV truck engine that replaced the LQ4, but it features variable valve timing. It equips the Chevrolet Silverado and Suburban from 2007 and the GMC Sierra and Yukon. Due to its smaller bore, it cannot use LS3 high performance rectangular orifice heads.

LFA / LZ1

Released in 2008, the LFA is an all-aluminum Vortec V8 and has been installed on GM’s GMT900 hybrid trucks and SUVs, including Tahoe, Yukon, Escalade, Silverado and Sierra models. The LFA features 10.8: 1 compression and produces 332 hp (248 kW). It was only offered on 2008 and 2009 models. A heavy overhaul of the LFA, the all-aluminum LZ1 truck and SUV engine, includes an upgraded electric throttle, new lubrication system, AFM and timing variable valves while continuing to pump 332 hp (248 kW). It was again offered in 2010-2013 in Tahoe, Yukon, Escalade, Silverado and Sierra GMT900 hybrid trucks and SUVs.

GM 4x4

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If truck engines have one downside, it’s that their camshafts typically have as much lift and duration as a joystick. Budget-conscious kilowatt fans building a forced induction LS should look to the factory LS9 cam upgrade, as the 211/230 / 122.5 specs are the best GMs ever offered in a blown motor.

LY2 / L20

First introduced in 2007 in GMC and Chevy trucks, the 4.8L Vortec 4800 LY2 replaced the Gen III LR4 and is the smallest member of the Gen IV family. The Iron Block V8 is also the only Gen IV truck and SUV engine that does not feature variable valve timing. It does between 260-295hp (194-220kW) depending on the application. The Vortec 4800 L20 is an iron-block Gen IV variant of the LY2, but comes equipped with variable valve timing on both intake and exhaust. It does not have AFM and makes 260-302hp (194-225kW).

LH6 / LH8 / LH9 / LC9

The LH6 is a 5.3L Vortec 5300 Gen IV V8 engine with AFM technology and is the aluminum variant of the LY5. It produces 315 hp (235 kW) and is found in the 2005-09 TrailBlazers, Envoy Denali, XL and XUV, Buick Rainiers, Saab 9-7X, Silverado 1500 and Sierra 1500. Vortec 5300 LH8 developing 300 hp (220 kW) were fitted to 2008-10 Hummer H3 SUVs and 2009-12 Colorado pickups, with a different crankcase layout to fit the engine compartments of GMT345 and GMT355 trucks, but without AFM . The Vortec 5300 LC9 is a four-wheel drive, Gen IV flex-fuel ready equipment making between 315 hp (235 kW, in pickups) and 320 hp (239 kW in SUV). It was installed on Avalanches, Silverados, Suburbans and Sierras from 2007. Variable valve timing was added to LH6 and LC9 after 2010.

LS engines

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Most Street Machine readers can identify “banana bunch” style LS car intake manifolds, but truck and SUV intake manifolds are taller because they have longer intake channels. They might not look as good, but they help produce some great torque figures

LY5 / LMG

The LY5 is an iron-block Vortec 5300 engine that replaced the Gen III LM7 engine in 2007. SUV equipment produces 320 hp (239 kW) while van equipment engines produce 315-320 hp (235- 239 kW). The LMG is the same as the LY5, except that it is the flex-fuel variant. LY5 and LMG engines are found in Avalanches, Silverados, Half-ton Suburbans, Tahoes, Sierras and Yukons from 2007. After 2010, these engines both achieved variable timing. valves, although the LMG does not have an AFM.

BORE BLOCK 4.06in
L92 / L9H / L94

As of 2007, the Cadillac Escalade featured the new Vortec 6200 L92, the 6.2L all-aluminum V8. Featuring two-stage variable valve timing, it produced 403 hp (301 kW) and was also found in GMC Sierra Denali and SLT and GMC Yukon, as well as in the H2 Hummers, Silverado and Tahoe LTZ export models. In 2009 the L92 was modified for flex-fuel capability and renamed L9H, while it was renamed again to L94 when AFM technology was added in 2010.

CHOOSE A WINNER

Determining if the windfall engine you’ve found is a Gen III or Gen IV is relatively easy. For starters, the Gen IV engines – as a whole – all have electronic throttle bodies, while the Gen III engines use cable throttles.

LS engines

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Don’t worry if you are looking at a long, bare engine, as there are a few generational signatures to these engines that are nearly impossible to tamper with.

LS engines

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Gen III cam sensors are found at the rear of the block, while Gen IV sensors are molded into the front timing case. The crank sensor is also different between Gen III and IV, although it is in the same position on the block. The Gen IIIs use a black sensor and 24-tooth trigger dial, while the latest Gen IV crank sensors are gray and 58-tooth.

HEAD STRESS

CASTING NUMBERS ENGINE FAMILY VALVE IN / EX BEDROOM CC
CATHEDRAL-PORT
241 LS1 2.00 / 1.55 67cc
243/799/823 LS1 / LS6 2.00 / 1.55 65cc
706/862/895 LM4 / LM7 / LR4 1.89 / 1.55 61cc
853/806/933 LS1 (perimeter) 2.00 / 1.55 67cc
RECTANGULAR PORT
317/035 LQ4 / LQ9 2.00 / 1.55 71cc
373/873 LQ4 2.00 / 1.55 71cc
364/716/823 L92 / LS3 2.165 / 1.59 68cc
452 LS7 2.20 / 1.61 70cc

BORE / CUT

Capacity Bore / Stroke (inch)
4807cc / 293ci 3.78 / 3.27
5328cc / 325ci 3.78 / 3.62
5665cc / 346ci 3.89 / 3.62
5967cc / 364ci 4.00 / 3.62
6.2L / 376ci 4.065 / 3.62
7.0L / 427ci 4.125 / 400
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Gail Mena

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