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Chevrolet 90-Degree V6 engine
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The Chevrolet 90° V6 family of engines began in 1978 with the Chevrolet 200 cid (3.3 L) V6 as the base engine for the all new 1978 Chevrolet Malibu. This engine family is still produced today, as the 4.3 L V6 engine used in Chevrolet trucks and vans.
These engines have a 90° vee 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.
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Encyclopedia
The Chevrolet 90° V6 family of engines began in 1978 with the Chevrolet 200 cid (3.3 L) V6 as the base engine for the all new 1978 Chevrolet Malibu. This engine family is still produced today, as the 4.3 L V6 engine used in Chevrolet trucks and vans.
These engines have a 90° vee 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 4.4" bore spacing and 9.025" 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. All the engines use a 1-6-5-4-3-2 firing order. The engines in this family are longitudinal engines, and have only been used in rear-wheel drive cars and trucks.
3.3L (200 CID)
Introduced in 1978, the 200 cid replaced the larger 250 cid as the base engine for Chevrolet's new downsized intermediate line. The 200 cid used a unique 3.5" bore and a 3.48" stroke similar to the Chevrolet 305 cid and 350 cid V8 engines. These bore and stroke dimensions were later used by the 267 cid V8 Cheverolet engine. Also like the small block V8 engines, the 200 cid V6 used 2.45" main bearings and 2.10" 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 0.050" narrower ends as well as a thrust bearing to be installed between each pair of rods. However, the connecting rods were still the same 5.7" in length as most other small block Chevrolet V8 engines. This produced an engine that with a semi-even fire sequence of 132 deg./108 degrees.
The 200 cid V6 was only produced for 1978 and 1979. It was only ever available with a 2-barrel carburetor. In 1978, the 200 cid used the Rochester 2GC carburetor and in 1979 it used a Rochester Dualjet carburetor. The smaller carburetor caused a slight decrease in power.
| Year | Horsepower | Torque | Bore and Stroke | Carburetor | Compression Ratio |
|---|
| 1978 | | | 3.50" x 3.48" | 2-BBL 2GC | 8.20:1 | |
| 1979 | | | 3.50" x 3.48" | 2-BBL M2ME | 8.20:1 | |
3.8L (229 CID)
The 229 cid engine was first introduced for the 1980 model year and was produced until 1984. This engine replaced the 250 cid in fullsize Chevrolets and Camaros as the new base V6. Additionally, the intermediate Chevrolet Malibu and Monte Carlo also used the 229 cid as a replacement for both the 200 cid V6, and the 231 cid Buick V6. Both the 231 cid Buick V6 and the 229 cid 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 229 cid has a 3.736" bore and a 3.48" stoke, identical to the Chevrolet 305 cid V8 engine. The 229 cid used the same 2.45" main bearing and 2.10" rod bearing diameters as the 200 cid V6 engine. Also like the 200 cid V6, the 229 cid used the same crankshaft with the 18 degree offset throws and the same 5.7" connecting rods with 0.050" narrowed ends. It came equipped with 1.84" intake valves and 1.50" exhaust valves. The 229 cid V6 was only equipped with a 2-barrel carburetor. For 1980 the 229 cid used a mechanical Dualjet. From 1981 - 1984 the electronic Dualjet was used along with the GM's CCC (Computer Command Control) system. The 229 cid was rated between 110 and .
| Year | Horsepower | Torque | Bore and Stroke | Carburetor | Compression Ratio |
|---|
| 1980 | | | 3.736" x 3.48" | 2-BBL M2ME | 8.60:1 | | 1981-82 | | | 3.736" x 3.48" | 2-BBL E2ME | 8.60:1 | | 1983-84 | | | 3.736" x 3.48" | 2-BBL E2ME | 8.60:1 | |
4.3L (262 CID)
The 4.3L (262 cid) 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 229 cid V6 in the fullsize Chevrolet and the Chevrolet El Camino. It also replaced the 250 cid in the Chevrolet fullsize trucks and fullsize vans as the new base six cylinder engine.
The 4.3L V6 has a 4.00" bore and a 3.48" stroke, identical to the 350 cid Chevrolet V8 engine. To create a true even fire engine, Chevrolet produced a crankshaft with 30 degree offsets between each rod pin. Consequentially, rod journals were increased to a larger 2.25". The connecting rods used on the 4.3L are therefore unique to this engine, being 5.7" in length, but having the larger 2.25" journals. The 4.3L also used larger valves than the 229 cid V6, with a 1.94" intake valve and a 1.50" exhaust valve.
In 1986 and 1987, the 4.3L 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 once 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 4.3L had its block design modified to allow a balance shaft to be installed. Even though the 4.3L is an even fire V6, the 90 degree block layout is not ideal for smoothness. The balance shaft on the 4.3L is installed above the top timing gear, and runs through the top of the lifter valley. It is gear driven off the timing chain, and therefore a new timing chain cover was designed for these balanced 4.3L V6s.
LB1 and LB4
In 1985, the 4.3L was either equipped with throttle-body fuel injection, RPO LB4 or a Rochester Quadrajet 4-Barrel carburetor, RPO LB1. The Chevrolet fullsize sedans and the Chevrolet El Camino 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 4.3L V6s until present day.
In 1986, the 4.3L engine used in the Chevrolet Caprice and El Camino 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 fullsize vans were upgraded to use the LB4 throttle-body injection version of the 4.3L. From 1987 onwards LB4s output was for pickups, while fullsize vans were rated at . In 1988 the S-series trucks and S-Blazer and Jimmys had the LB4 4.3L as an available option (the accessory drive was upgraded to a serpentine belt drive). The LB4 continued until 1996 with minor variations in power, but without any major change.
| Year | Horsepower | Torque | Fuel System | Compression Ratio | RPO | Applications |
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| 1985-86 | | | 4-BBL | 9.3:1 | LB1 | 1,2,3 | | 1985 | | | TBI | 9.3:1 | LB4 | 4,5 | | 1986-90 | | | TBI | 9.3:1 | LB4 | 4,5 | | 1987-88 | | | TBI | 9.3:1 | LB4 | 5 | | 1986 | | | TBI | 9.3:1 | LB4 | 3 | | 1987-92 | | | TBI | 9.3:1 | LB4 | 2 | | 1987-92 | | | TBI | 9.1:1 | LB4 | 1,3,6,7 | | 1993-95 | | | TBI | 9.1:1 | LB4 | 2 | | 1993-95 | | | TBI | 9.1:1 | LB4 | 1,3,6,7 | |
Legend
LU2
For the 1990-1991 model years a high ouotput 4.3L 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.
| Year | Horsepower | Torque | Fuel System | Compression Ratio | RPO | Applications |
|---|
| 1990-92 | | | TBI | 9.1:1 | LU2 | 1 | |
Legend
- 1 - Chevrolet Astro vans, GMC Safari Vans - optional on extended length models
L35 CPI
1992 introduced a new version of the 4.3L, the L35. This version of the 4.3L was equipped with CPI (Central Port Fuel Injection). This system had one centrally located fuel injector distribute fuel to six hoses each with a poppet valve to each of the intake ports. This system allowed for a multi-point 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 S-10 Blazers and S15-Jimmys and Astro and Safari vans only. The L35 was rated at and of torque.
| Year | Horsepower | Torque | Fuel System | Compression Ratio | RPO | Applications |
|---|
| 1992-94 | | | CPI | 9.1:1 | L35 | 1,2,3 | | 1995 | | | CPI | 9.1:1 | L35 | 1 | | 1995 | | | CPI | 9.1:1 | L35 | 3 | | 1995 | | | CPI | 9.1:1 | L35 | 2 | |
Legend
L35 and LF6 SCPI
Major design changes to the 4.3L V6 for the 1996 model year. Like other small block Chevrolet V8s, the 4.3L engine received redesigned heads which had improved airflow and combustion efficiency. These heads are referred to as Vortec heads. Furthermore the 4.3L was upgraded to receive sequential port fuel injection. The fuel system uses six centrally mounted injectors firing into six nylon hoses with poppet valves leading to each intake port. This system was call SCPI (Sequential Central Port Injection). This 4.3L used a two piece manifold, with the upper half manufactured from a composite plastic and the lower half manufactured from cast aluminum.
This engine came in two versions, the LF6 rated at - , and the L35 rated at 180 - . Only the S-series pick-ups used the LF6, while the fullsize trucks, vans and Blazer and Jimmy used the L35 version. The L35 was optional on the S-Series trucks.
| Year | Horsepower | Torque | Fuel System | Compression Ratio | RPO | Applications |
|---|
| 1996 | | | SCPI | 9.2:1 | LF6 | 5 | | 1997-2002 | | | SCPI | 9.2:1 | LF6 | 5 | | 1996-2002 | | | SCPI | 9.2:1 | LF6 | 6 | | 1996-2002 | | | SCPI | 9.2:1 | L35 | 5 | | 1996-2002 | | | SCPI | 9.2:1 | L35 | 3,4,6 | | 1996-2002 | | | SCPI | 9.2:1 | L35 | 2 | | 1996-1998 | | | SCPI | 9.2:1 | L35 | 1 | | 1999-2002 | | | SCPI | 9.2:1 | L35 | 7 | |
Legend
LU3 and LG3 MPFI
2002 saw major changes to the 4.3L fuel injection system. For 2002 California emission Chevrolet Astros, GMC Safaris, Chevrolet Silverados and GMC Sierras all came equipped with the updated LU3 4.3L. 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 4.3L 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. 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 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 fullsize 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 190-200 hp and 250-260 ft·lbf of torque.
| Year | Horsepower | Torque | Fuel System | Compression Ratio | RPO | Applications |
|---|
| 2003 | | | MPFI | 9.2:1 | LG3 | 5 | | 2003-05 | | | MPFI | 9.2:1 | LU3 | 3,4,6 | | 2002-2003 | | | MPFI | 9.2:1 | LU3 | 2 | | 2002-2003 | | | MPFI | 9.2:1 | LU3 | 1 | | 2004-2009 | | | MPFI | 9.2:1 | LU3 | 1,2 | |
Legend
Turbocharged LB4 4.3L V6
In 1991 GMC introduced the GMC Syclone limited edition truck that used a turbocharged 4.3L 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 natuarally aspired LB4's long-block was shared with the turbo version. However, the vehicles that used the 4.3L 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 48 mm twin-bore throttle body from the 5.7L TPI Corvette engine was used on the engine's top end.
The Turbocharged 4.3L was last used in the GMC Typhoon in the 1993 model year. The engine produced @ 4400 rpm and of torque @ 3600 rpm.
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