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 and first used in the 2014 Silverado/Sierra 1500 trucks.

Generation I These engines have a 90° V-block with twelve 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, some bearings, piston assemblies, lubrication and cooling system components, and external accessories. The 90° 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 90° V6 and Small Block Chevrolet assembly lines (for engines manufactured after 1979) 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. Until 2014, the Chevrolet 90° V6 was produced at the GM Powertrain Division plant in Romulus, Michigan.

3.3L (200 CID)

Introduced in 1978, the replaced the larger as the base engine for Chevrolet's new downsized intermediate line. The used a unique bore and stroke (the Chevrolet V8 engines shared the same stroke dimension). These bore and stroke dimensions were later used by the V8 Chevrolet engine. Also like the small block V8 engines, the V6 used main bearings and rod bearing diameters.

Being a 90° 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 Ratio1978 @ 3800 rpm @ 2000 rpm2-BBL 2GC8.2:11979 @ 4000 rpm @ 2000 rpm 2-BBL M2ME

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 base six-cylinder engine. 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° V6 engines, and are often referred to as the 3.8L V6. These engines should not be confused as being the same, and are 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 (Computer Command Control) system. The was rated between 110 and .

YearHorsepowerTorqueBore and StrokeCarburetorCompression Ratio1980 at 4,000 rpm at 2,000 rpm2-BBL M2ME8.6:11981–1982 at 4,200 rpm at 2,000 rpm2-BBL E2ME1983–1984 at 4,000 rpm at 1,600 rpm

4.3L (262 CID)

The V6 is the last and most successful engine in the Chevrolet 90° 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 in the Chevrolet and GMC full-size trucks and full-size vans, and in 1990, it replaced the 292 cu in (4.8 L) in the Step-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 (also shared with the 350).

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° 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 engines which retained the cast-in boss.

For the 2007 model year, the distributor was eliminated in place of a coil-on-plug ignition system (using a 58x crankshaft position sensor based on the GEN IV LSx). This resulted in a redesigned timing cover with a wider bottom flange, making it incompatible with the 1996–06 LU3/L35. The only vehicles using the new revision of the were the half-ton versions of the Chevrolet Silverado/GMC Sierra (2007–2013) and Chevrolet Express/GMC Savana (2008–2014).

LB1 and LB4

In 1985, the was either equipped with throttle-body fuel injection (RPO LB4) or a Rochester Quadrajet four-barrel carburetor (RPO LB1). The Chevrolet Caprice, Chevrolet Monte Carlo, Chevrolet El Camino, Pontiac Parisienne, and Pontiac Grand Prix used the LB4 rated at . Pickups and vans used the LB1 version rated at . The LB1 used in trucks and vans was referred to as Vortec in Chevrolet literature (named after a combustion chamber design known as a swirl port which twists the fuel mix from the intake ports as introduced with the Cavalier's 2.0L engine), and this name continued to be used with all truck and van V6s until 2014.

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 (RPO 9C6) and police (RPO 9C1) 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 pickups and 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 (marine applications had the fuel pump boss drilled and tapped).

From 1987 onwards, the LB4's output was for pickups, while full-size vans were rated at . In 1988, the S-10/S-15 trucks, S-10 Blazer, and S-15 Jimmy had the LB4 as an available option (the accessory drive was upgraded to a serpentine belt drive), which later replaced the less powerful 60° V6 offering (2.8L). The LB4 continued until 1996 with minor variations in power, but without any major changes. 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 RatioRPOApplications1985–1986 @ 4000 rpm@ 2400 rpm4-barrel9.3:1LB11, 2, 31985 @ 3600 rpm@ 2000 rpmTBILB44, 51986–1990 @ 4000 rpm@ 2000 rpm1987–1988 @ 4200 rpm 51986 @ 4000 rpm@ 2400 rpm 31987–1992 @ 4000 rpm@ 2400 rpm 8.6:1LB42@ 4000 rpm@ 2400 rpm9.1:1LB41, 3, 6, 71993–1995 @ 4000 rpm@ 2000 rpm 2@ 4000 rpm@ 2000 rpm 1, 3, 6, 7

Legend

1 – Chevrolet C/K trucks, GMC C/K trucks 2 – Chevrolet G-series vans, GMC G-Series vans 3 – Chevrolet Astro vans, GMC Safari vans (Note: LB1 for 1985 only and LB4 not available 1995) 4 – 1985 Chevrolet Impala, 1985–1988 Chevrolet Caprice, 1989–1990 Chevrolet Caprice police/taxi only, 1985–1986 Pontiac Parisienne 5 – 1985–1988 Chevrolet El Camino, GMC Caballero, Chevrolet Monte Carlo, 1986–1987 Pontiac Grand Prix (Note: LB4 used 1986 only) 6 – 1988–1994 Chevrolet S-10 Blazer, GMC S-15 Jimmy, and 1991 Oldsmobile Bravada 7 – 1988–1995 Chevrolet S-10 and GMC S-15/Sonoma

LU2

For the 1990–1991 model years, a high-output V6 was an available option for the extended-length versions of 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 RatioRPOApplications1990–1992 @ 4600 rpm @ 3400 rpmTBI9.1:1LU21

Legend

1 – Chevrolet Astro vans, GMC Safari vans; optional on extended-length models only

L35 CPI

1992 introduced a new version of the , the L35. This version of the was equipped with CPI (Central Port Fuel Injection). 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/GMC Sonoma pickups, Chevrolet S-10 Blazer/GMC S-15 Jimmy/Oldsmobile Bravada SUVs, and Chevrolet Astro/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 (10238181 casting) used with the L35 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 six-bolt timing cover; some engines had a crankshaft position sensor (in conjunction with a redesigned distributor containing a pickup assembly which functions as a camshaft position sensor) when OBD-II was phased in.

YearHorsepowerTorqueFuel SystemCompression RatioRPOApplications1992–1994 at 4,500 rpm at 3,600 rpmCPI9.1:1L351, 2, 31995 at 4,500 rpm at 3,400 rpm 1 at 4,500 rpm 3 at 4,500 rpm 2

Legend

1 – Chevrolet Astro vans, GMC Safari vans (Note: standard on AWD, optional on 2WD models) 2 – Chevrolet S-10 Blazer, GMC Jimmy, Oldsmobile Bravada (Note: Oldsmobile Bravada not produced in 1995) 3 – Chevrolet S-10, GMC Sonoma (engine standard equipment with the S10 SS and Sonoma GT)

L35 and LF6 SCPI and MPFI