GM 5.7L (350) Vortec Engine

Although all of Chevrolet’s siblings of the period (Buick, Cadillac, Oldsmobile, Pontiac, and Holden) designed their own V8s, it was the Chevrolet 305 and 350 cu in (5.0 and 5.7 L) small-block that became the GM corporate standard. Over the years, every American General Motors division except Saturn and Geo used it and its descendants in their vehicles.

In 1991, GM created a new-generation small-block engine called the “LT1 350”, distinct from the high-output Generation I LT-1 of the 1970s. It displaced 5.7 L (350 cu in), and was a 2-valve pushrod design. The LT1 used a reverse-flow cooling system which cooled the cylinder heads first, maintaining lower combustion chamber temperatures and allowing the engine to run at a higher compression than its immediate predecessors.

LT1 engine was used in:

Y-body:

  • 1992–1996 Chevrolet Corvette C4

F-body:

  • 1993–1997 Chevrolet Camaro Z28, B4C and SS
  • 1993–1997 Pontiac Firebird Formula, Trans Am, and Firehawk

B-body:

  • 1994-1996 Buick Roadmaster
  • 1994–1996 Chevrolet Caprice
  • 1994–1996 Chevrolet Caprice Police Package
  • 1994–1996 Chevrolet Impala SS
  • 1994–1996 Chevrolet Caprice Wagon
  • 1994–1996 Buick Roadmaster Wagon

D-body:

  • 1994–1996 Cadillac Fleetwood

There were a few different versions of the LT1. All feature a cast iron block, with aluminum heads in the Y and F bodies, and cast iron heads in the B and D bodies. Corvette blocks had four-bolt main caps, while most other blocks were two-bolt main caps. Block castings remained the same between 2 and 4 bolt mains.

The 92–93 LT1s used speed density fuel management, batch-fire fuel injection and a dedicated Engine Control Module (ECM). In 94 the LT1 switched to a mass airflow sensor and sequential port injection. A new, more capable computer controlled the transmission as well as the engine and got a new name: Powertrain Control Module (PCM). Where the ECM held its calibration information in a replaceable PROM chip, the 94-95 OBD1 PCMs are reprogrammable through the diagnostic port.

The LT4 was available on the following vehicles:

  • 1996 Chevrolet Corvette only when equipped with 6-speed manual transmission (includes all Grand Sports) (Production: 6,359)
  • 1997 Chevrolet Camaro SLP/LT4 SS 6-speed (Production: 100 for the U.S., 6 for Canada. There were 2 prototypes)
  • 1997 Pontiac Firebird SLP/LT4 Firehawk 6-speed (Production: 29)

The LT4 was the special high-performance version of the new-generation LT1. It featured a slightly more aggressive camshaft profile, 1.6:1 aluminum roller rocker arms, lighter hollow intake valves and liquid-sodium filled exhaust valves, larger fuel injectors, performance crankshaft, higher 10.8:1 compression ratio and high-flow intake manifold (painted red) with extra material above the port available to allow port matching to the raised port LT4 cylinder heads. The LT4 was conservatively underrated at 330 hp (246 kW) and 340 lb⋅ft (461 N⋅m). It was introduced in the 1996 model year, for the last year of the C4 Corvette, and came standard on all manual transmission (ZF 6-speed equipped) C4 Corvettes. The engine was passed down to 1997 SLP Camaros SS and SLP Firehawks with 6-speed manual transmissions.

For model year 1990, Chevrolet released the Corvette ZR-1 with the radical Lotus Engineering-designed double overhead cam LT5 engine. Engineered in the UK but produced and assembled in Stillwater Oklahoma by specialty engine builder Mercury Marine, the all-aluminum LT5 shared only the 4.4 inch bore spacing with any previous sbc engine. It does not have reverse cooling and is generally not considered a small block Chevrolet.

The LT5 was available on the following vehicles:

  • 1990-1995 Chevrolet Corvette C4 ZR-1 equipped with 6-speed manual transmission (Production: 6,939). Although the LT5 was never used in another production GM vehicle, it did make its way into several Corvette concepts, race cars and even into a limited run of the Lotus Elise GT1.
Gen I Years Engine option code (VIN identifier) Power (hp) Torque (lb.-ft.) Displacement (c.i.) Fuel (octane) Bore x Stroke (in) Compression ratio Block & heads (iron or aluminum) Block features
I 1996 – 02 L30 (M) 220@4600 290@2800 305 3.743 x 3.48 9.1:1 Iron Truck/van only
I 1987 – 95 L03 (E/H) 170@4400 255@2400 305 3.743 x 3.48 9.1:1 Iron TBI; passenger car used roller cam
I 1988 – 96 L05 (K) 210@4400 300@2800 350 4.0 x 3.48 9.3:1 Iron TBI; 9C1 optioned Caprice and F-bodies had hydraulic roller cam
I 1978 – 88 LG4 (F/H) 150-170@4600 240-250@2800 305 3.743 x 3.48 8.6:1 Iron 4bbl Quadrajet
I 1981 – 86 LE9 (F) 165@4400 240@2000 305 3.743 x 3.48 9.5:1 Iron Truck/Van only – electronic spark control module used
I 1982 – 83 LU5 165-175 305 3.743 x 3.48 ?:1 Iron “Crossfire EFI 5.0L”
I 1967 – 80 L48 (K) 165-195 380 350 4.0 x 3.48 8.25-10.5:1 Iron
I 1969 – 70 L46 350 350 93req 4.0 x 3.48 11.0:1 Iron Corvette only
I 1969 – 76 L65 145 220 350 87 4.0 x 3.48 8.5:1 Iron 2bbl
I 1969 – 88 LM1 (L) 155-175 350 4.0 x 3.48 Iron 4bbl Rochester Quadrajet (4MV, M4MC, E4ME); retail option until 1981 when last used with the Camaro Z28; post-1980 use of the LM1 was for 9C1-optioned B (Caprice, Impala) and G-bodies (Malibu)
I 1970 – 74 ZQ3 190-300 270-3500 350 4.0 x 3.48 8.5-10.25:1 Iron 4bbl, Corvette. L48 camshaft
I 1970 – 72 LT1 250-370@6000 270-300@4000 350 4.0 x 3.48 9.1:1 Iron 4bbl
II 1992 – 97 LT1 (P) 260-305@4800-5200 325-340@2400-3400 350 91 OCTANE 4.0 x 3.48 10.4:1 Iron (Aluminum FOR F and Y Bodies) Reverse Flow Heads
I 1973 – 80 L82 205-250 255-285 350 4.0 x 3.48 9:1 Iron 4bbl Rochester Quadrajet; flat top pistons with a D-shaped relief cut for valve clearance
I 1981 L81 190 280 350 4.0 x 3.48 8.2:1 Iron 4bbl Rochester Quadrajet (E4ME), Corvette
I 1970 – 86 LS9 (L) 165@3800 275@1600 350 4.0 x 3.48 8.2:1 Iron 4bbl, truck
I 1981 – 86 LT9 (M) 160@3800 250@2800 350 4.0 x 3.48 8.3:1 Iron 4bbl, truck
I 1982 – 84 L83 200-205 285-290 350 4.0 x 3.48 9.0:1 Iron CrossFire
I 1985-92 L98 (8) 225-250@4000 330-345@3200 350 4.0 x 3.48 9.5-10:1 Iron/Aluminum (Corvette) TPI
I 1996-02 L31 (R) 255-350@4600 330-350@2800 350 4.0 x 3.48 Iron truck, Vortec
I 1970-80 245-265 400 4.120 x 3.75 Iron 70-72 4bolt main, 73-80 2bolt main
I 1975-76 110 133@3600 262 3.671 x 3.1 Iron Nova and Monza only; 2bbl Rochester 2GC carburetor
I 1994-96 L99 (W) 200 245 263 3.736 x 3.0 Iron reverse cooling, Caprice, special ops, police vehicles
I 1983-88 L69 (G) 180-190@4800 240@3200 305 3.743 x 3.48 9.5:1 Iron H.O., Firebird/Camaro, Monte Carlo SS only
I 1985-92 LB9 (F) 190-230 275-300 305 3.743 x 3.48 Iron TPI, Firebird/Camaro only
I 1976-82 LG3 (U) 145@4400 245@2400 305 3.743 x 3.48 8.5:1 Iron 2bbl

 

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