General Motors 90° V6 engine


The Chevrolet 90° V6 family of V6 engines began in 1978 with the Chevrolet as the base engine for the all new 1978 Chevrolet Malibu. The original engine family was phased out in early 2014, with its final use as the V6 engine used in Chevrolet and GMC trucks and vans. Its phaseout marks the end of an era of Chevrolet small-block engine designs dating back to the 1955 model year. A new Generation V V6 variant entered production in late 2013, based on the LT1 small block V8 used in the 2014 Chevrolet Silverado.

Generation I

These engines have a 90° V-block with 12 valves activated by a pushrod valvetrain. All engines have cast iron blocks and cylinder heads. The engines are based on the Chevrolet Small-Block engine, and the V6 is formed by the removal of the #3 and #6 cylinders. The V6s share the same bore spacing and deck height as the V8 engines. Many parts are interchangeable between the 90° V6 and the small block V8 including valvetrain components, bearings, piston assemblies, lubrication and cooling system components, and external accessories. The 90-degree V6 engine uses the same transmission bellhousing pattern as the Chevrolet small-block V8 engine. The oil pan dipstick is located on the passenger side above the oil pan rail; this design was phased in on both the V6-90 and Small Block Chevrolet assembly lines sharing the same casting dies. All the engines use a 1-6-5-4-3-2 firing order. The engines in this family are longitudinal engines, and have been used in rear-wheel drive cars and trucks, industrial, and marine applications. As of 2012, the Chevrolet 90° V6 is currently produced at the GM Powertrain Division plant in Romulus, Michigan.

3.3L (200 CID)

Introduced in 1978, the replaced the larger Chevrolet Straight-6 engine#250| as the base engine for Chevrolet's new downsized intermediate line. The used a unique bore and stroke. These bore and stroke dimensions were later used by the Chevrolet Small-Block engine#267| V8 Chevrolet engine. Also like the small block V8 engines, the V6 used main bearings and rod bearing diameters.
Being a 90-degree V6, Chevrolet took steps to eliminate the rough running tendencies of the 200. The crankshaft has each of its connecting rod throws offset by 18 degrees for each pair of rods. This required the connecting rods to have narrower ends as well as a thrust bearing to be installed between each pair of rods. However, the connecting rods were still the same length as most other small-block Chevrolet V8 engines. This produced an engine with a semi-even fire sequence of 132 degrees/108 degrees.
The V6 was only produced for 1978 and 1979. It was available only with a 2-barrel carburetor. In 1978, the used the Rochester 2GC carburetor and in 1979 it used a Rochester Dualjet carburetor. The smaller Dualjet carburetor caused a slight decrease in power.
YearHorsepowerTorqueBore and StrokeCarburetorCompression Ratio
1978 @ 3800 rpm @ 2000 rpm2-BBL 2GC8.2:1
1979 @ 4000 rpm @ 2000 rpm2-BBL M2ME8.2:1

3.8L (229 CID)

The engine was first introduced for the 1980 model year. This engine replaced the straight-six in full-size Chevrolets and Camaros as the new base V6. Additionally, the intermediate Chevrolet Malibu and Monte Carlo also used the as a replacement for both the V6 and the Buick V6. Checker Motors Corporation also used this engine starting with its 1980 A11 Taxi and A12 Marathon sedans. Both the Buick V6 and the Chevrolet V6 are 90-degree V6 engines, and both are often referred to as the 3.8L V6. These engines should not be confused as being the same, and are completely unique engine designs.
The has a bore and stroke, identical to the Chevrolet V8 engine. The used the same main bearing and rod bearing diameters as the V6 engine. Also like the V6, the used the same crankshaft with the 18-degree offset throws and the same connecting rods with narrowed ends. It came equipped with intake valves and exhaust valves. The V6 was only equipped with a 2-barrel carburetor. For 1980 the used a mechanical Dualjet. From 1981 to 1984 the electronic Dualjet was used along with the GM's CCC system. The was rated between 110 and.
YearHorsepowerTorqueBore and StrokeCarburetorCompression Ratio
1980 at 4,000 rpm at 2,000 rpm2-BBL M2ME8.6:1
1981–1982 at 4,200 rpm at 2,000 rpm2-BBL E2ME8.6:1
1983–1984 at 4,000 rpm at 1,600 rpm2-BBL E2ME8.6:1

4.3L (262 CID)

The V6 is the last and most successful engine in the Chevrolet 90-degree V6 engine family. This engine was introduced in 1985 as a replacement for the V6 in the full-size Chevrolet, the Chevrolet El Camino and Chevrolet Monte Carlo. It also replaced the Chevrolet Straight-6 engine#250| in the Chevrolet full-size trucks and full-size vans as the new base six-cylinder engine.
The V6 has a bore and stroke, identical to the Chevrolet V8 engine. To create a true even fire engine, Chevrolet produced a crankshaft with 30-degree offsets between each rod pin. Consequently, rod journals were increased to a larger. The connecting rods used on the are therefore unique to this engine, being in length, but having the larger journals. The also used larger valves than the V6, with a intake valve and a exhaust valve.
In 1986 and 1987, the engine saw engine design upgrades similar to the Chevrolet small block V8. In 1986, the rear main crankshaft oil seal was changed from a two piece to a one piece seal. Some 1985 model year vehicles would have a 1986 engine due to service replacement - cylinder blocks were shipped with oil pans. 1987 saw new center bolt valve covers and hydraulic roller lifters.
For the 1992 model year, the had its block design modified to allow a balance shaft to be installed. Even though the is an even fire V6, the 90-degree block layout is not ideal for smoothness. The balance shaft on the is installed above the camshaft and runs through the middle of the lifter valley. It is gear driven off the camshaft timing sprocket, and therefore a new timing chain cover was required for these balanced 4.3L V6s. Balance shaft engines do not have provisions for a mechanical fuel pump unlike the non-balance shaft motors which retained the cast in boss.
As of the 2013 model year, the was still in production although the distributor was eliminated in the late 2000s where a coil-on-plug ignition system was phased in. This resulted in a new design timing cover with a wider bottom flange, making it incompatible with the 1996-06 LU3/L35. The only vehicles using the by that time were the GMT900 light duty trucks and vans.
As of March 7, 2014, the last engine rolled off the line at Romulus Powertrain. Chevrolet Performance still lists the LU3 motor in their product catalog. Mercury Marine, which sells its engines under the MerCruiser brand developed the 4.5L V6 Mercruiser Engine, producing 200HP and 250HP each, based on the architecture using similar dimensions.

LB1 and LB4

In 1985, the was either equipped with throttle-body fuel injection, RPO LB4 or a Rochester Quadrajet 4-Barrel carburetor, RPO LB1. The Chevrolet Caprice, Chevrolet Monte Carlo, Chevrolet El Camino, Pontiac Parisienne, and Pontiac Grand Prix used the LB4 rated at. Pick-ups and Vans used the LB1 version rated at. The LB1 used in trucks and vans was referred to as Vortec in Chevrolet literature, and this name continued to be used with all truck and van V6s until present day.
In 1986, the engine used in passenger cars saw an increase in power to. This engine remained unchanged until 1990 when it was last used in taxi and Police Chevrolet Caprices. In 1986 the Chevrolet Astro and GMC Safari vans used the fuel-injected LB4 instead of the LB1. In 1987, the Chevrolet full size pick-ups and full-size vans were upgraded to use the LB4 throttle-body injection version of the. The mechanical fuel pump boss was retained but the hole was undrilled. From 1987 onwards LB4s output was for pickups, while full-size vans were rated at. In 1988 the S-series trucks and S-Blazer and Jimmys had the LB4 as an available option, which later replaced the 2.8 as the base V6. The LB4 continued until 1996 with minor variations in power, but without any major change. While a majority of LB4s did not have a balance shaft, some 1994 model year engines may have a balance shaft since production of the cylinder block used on the L35 was phased in for both induction systems. The 1994 model year was the final time a non-balance shaft cylinder block was used; production 1995 TBI engines were all balance shaft engines.
YearHorsepowerTorqueFuel SystemCompression RatioRPOApplications
1985–1986
@ 4000 rpm
@ 2400 rpm		4-BBL9.3:1LB11,2,3
1985
@ 3600 rpm
@ 2000 rpm		TBI9.3:1LB44,5
1986–1990
@ 4000 rpm
@ 2000 rpm		TBI9.3:1LB44,5
1987–1988
@ 4200 rpm
@ 2000 rpm		TBI9.3:1LB45
1986
@ 4000 rpm
@ 2400 rpm		TBI9.3:1LB43
1987–1992
@ 4000 rpm
@ 2400 rpm		TBI8.6:1LB4 2
1987–1992
@ 4000 rpm
@ 2400 rpm		TBI9.1:1LB41,3,6,7
1993–1995
@ 4000 rpm
@ 2000 rpm		TBI9.1:1LB42
1993–1995
@ 4000 rpm
@ 2000 rpm		TBI9.1:1LB41,3,6,7

Legend
For the 1990–1991 model years a high-output V6 was an available option for the Chevrolet Astro and GMC Safari vans. The LU2 used unique hypereutectic, strutless pistons and a more aggressive camshaft. Like the LB4, the LU2 used throttle-body fuel injection, but was rated at and of torque. This engine was replaced in 1992 with the L35.
YearHorsepowerTorqueFuel SystemCompression RatioRPOApplications
1990–1992 @ 4600 rpm @ 3400 rpmTBI9.1:1LU21

Legend
1992 introduced a new version of the, the L35. This version of the was equipped with CPI. This system had one centrally located fuel injector to distribute fuel to six hoses each with a poppet valve to each of the intake ports. This system allowed for a multi-point fuel injection, using one injector. The fuel injection was a batch fire system and used a two piece cast aluminum dual-plenum manifold. This engine was available in Chevrolet S-10 Pickups, Chevrolet C/K Pickups, and S10 Blazer/S15-Jimmys SUVs, Chevrolet Astro and GMC Safari vans only. The L35 was rated at and of torque.
The cylinder block was redesigned for use with a balance shaft. Cylinder heads used with the L35 will have intake ports with eyebrows that clear the fuel injectors. Timing cover flange area was thickened in 1995 when some of the balance shaft motors had a 6 bolt timing cover - some engines had a crankshaft position sensor when OBDII was phased in.
YearHorsepowerTorqueFuel SystemCompression RatioRPOApplications
1992–1994 at 4,500 rpm at 3,600 rpmCPI9.1:1L351,2,3
1995 at 4,500 rpm at 3,400 rpmCPI9.1:1L351
1995 at 4,500 rpm at 3,400 rpmCPI9.1:1L353
1995 at 4,500 rpm at 3,400 rpmCPI9.1:1L352

Legend
Major design changes were made to the V6 for the 1996 model year. Like other small block Chevrolet V8s, the engine received redesigned heads which had improved airflow and combustion efficiency. These heads are referred to as Vortec heads.
The engine block was revised with structural reinforcing ribs up front eliminating the two freeze plugs along with an alloy oil pan. The 1996+ cast aluminum oil pan has 12 bolts where a 16 bolt oil pan from the earlier 4.3 does not interchange. These came with a redesigned 4L60-E transmission with a removable bellhousing which bolts to the oil pan.
Crankshafts manufactured for the 1999 model year. The torque converter pilot hub is longer than the early 4L60E or the second generation variants with the GMT330 or 1996-2000 C/K series.
This engine came in two versions, the LF6 rated at, and the L35 rated at. Only the S-series pick-ups used the LF6, while the full-size trucks, vans and Blazer and Jimmy used the L35 version. The L35 was optional on the S-Series trucks.
YearHorsepowerTorqueFuel SystemCompression RatioRPOApplications
1996 at 4,400 rpm at 2,800 rpmSCPI9.2:1LF65
1997–2002 at 4,400 rpm at 2,800 rpmMPFI9.2:1LF65
1996–2002 at 4,400 rpm at 2,800 rpmSCPI9.2:1LF66
1996–2002 at 4,400 rpm at 2,800 rpmSCPI9.2:1L355
1996–2002 at 4,400 rpm at 2,800 rpmSCPI9.2:1L353,4,6
1996–2002 at 4,400 rpm at 2,800 rpmSCPI9.2:1L352
1996–1998 at 4,400 rpm at 2,800 rpmSCPI9.2:1L351
1999–2002 at 4,600 rpm at 2,800 rpmSCPI9.2:1L357

Legend
2002 saw major changes to the fuel-injection system. For 2002 California emission Chevrolet Astros, GMC Safaris, Chevrolet Silverados and GMC Sierras all came equipped with the updated LU3. 2003 saw the L35 discontinued and the LU3 replacing it in all other applications. A new variation was also introduced in 2003, the LG3. For 2004 to 2009 the LU3 has been the only produced.
The biggest change to the LU3 and LG3 was the fuel-injection system. These engines used a multipoint fuel-injection system, with six Multec II fuel injectors mounted at each intake port on the manifold. GM recommends the Multec II spider assembly as a replacement for the 1996-01 CPI injector/spider assembly since the poppet valves have been known to stick open. The sticking poppet valves have been attributed to ethanol fuel blends sold in the State of California. The composite upper intake manifold and cast aluminum lower intake from the L35 engine is also used on the LU3. The LG3 uses a cast aluminum upper intake and a cast iron lower intake. The lower intake eliminated the EGR valve.
The LU3 also received a quiet cam to help reduce vibration at both idle and high engine speeds. This camshaft used the same lift and duration as the older design, but the cam was reprofiled to keep the valve lifters in full contact with the cam lobes as the cam ramps down.
The LG3 was used in Chevrolet and GMC S-series pickups and was only produced for 2003. The LU3 was used in the Chevrolet and GMC full-size trucks and vans, the Chevrolet Astro and GMC Safari vans and the Chevrolet S-10 Blazer and GMC S-15 Jimmy. The LG3 was rated at and of torque. The LU3 was rated at and of torque.
For the 2007+ GMT900 Silverado/Sierra trucks, the LU3 engine received a Distributorless Ignition System - the traditional distributor was eliminated where a stub shaft was used. Also the crankshaft sensor was upgraded to a 58x reluctor wheel which resulted in the timing cover redesigned
  • 6 - Chevrolet S-10 and GMC Sonoma

    Turbocharged LB4 4.3L V6

In 1991 GMC introduced the GMC Syclone limited edition truck that used a turbocharged V6. This engine used a Mitsubishi TD06-17C turbocharger, Garrett Water/Air intercooler and electronic multi-point fuel injection. Although GM made these modifications to the engine, it was still referred to with the RPO LB4 code. The majority of the naturally aspirated LB4's long-block was shared with the turbo version. However, the vehicles that used the turbo engine also included RPO code ZR9. Internal engine upgrades included nodular iron main bearing caps, graphite composite head gaskets with stainless steel flanges and hypereutectic pistons which lowered the engine compression to 8.35:1. A unique intake manifold that used the twin-bore throttle body from the 5.7L TPI Corvette engine was used on the engine's top end.
The Turbocharged was last used in the GMC Typhoon in the 1993 model year. The engine produced at 4400 rpm and of torque at 3600 rpm.

Generation V

4.3L (262 CID)

Commencing with the 2014 model year, a new LV3 EcoTec3 4300, based on GM's GEN V Small Block V8, will become the new base motor for the next generation Chevrolet Silverado/GMC Sierra light duty trucks, and will be phased in throughout the rest of the truck/van line after the 2015 model year, signaling an end to a design dating back to 1955. Like its small block V8 counterparts, GM Powertrain also sells the motor for marine and industrial applications.

LV3

The LV3 V6 is a new engine announced by GM at the end of 2012. GM considers this a new engine design which inherits from its predecessors its displacement, 2-valve pushrod valvetrain, 90-degree cylinder angle, and bore centers. It is based on the fifth generation LT engine and includes the same features such as direct injection, piston cooling jets, active fuel management, variable displacement oil pump, continuously variable valve timing and aluminum cylinder heads and block. The engine is SAE certified to at 5300 rpm and at 3900 rpm on regular unleaded gasoline and at 5300 rpm and at 3900 rpm on E85. Emissions are controlled by a close-coupled catalytic converter, Quick Sync 58X ignition, returnless fuel rail, fast-response O2 sensor. It was launched in the all-new 2014 Chevrolet Silverado 1500 and 2014 GMC Sierra 1500.
Applications:
  • 2014–present Chevrolet Silverado 1500
  • 2014–present GMC Sierra 1500