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LT1/LT4 Engine
'92 - '93 GM's generation II engine, the LT1, was introduced in '92 in the corvette and was rated at 300hp. In 93 the new 4th Gen. F-body arrived with the LT1 rated at 275hp. There are some significant differences between the new engine and earlier small blocks. Among them are the opti-spark distributor located on the front of the engine behind the gear driven water pump and crank balancer. The block, heads, timing cover, water pump, intake manifold and accessory brackets are not interchangeable with the earlier small blocks. Engine mounts and the bell-housing pattern remains the same. There were early and later versions of the aluminum head. The early head had a casting number of 10128374 and the later head had a casting number of 10128649.
The LT1 is reverse flow cooled meaning the water flows through the heads first then the block, instead of through the block and then the heads as is standard. Reverse flow cooling is a function of engine design and does not require a special radiator. An overflow tank is necessary to ensure there is no air in the system.
There are some differences between LT1's. The Corvette got 4 bolt mains and Aluminum heads. The F-body cars got 2 bolt mains and aluminum heads. The '94 - '96 Buick Roadmaster, Cadillac Fleetwood, Chevrolet Caprice, police cars and the Impala SS got the 5.7L with 2 bolt mains and cast iron heads and was rated at 265hp. There was also a 4.3L LT1 available in the big cars which is indistinguishable from the 5.7L, except for the different casting number and 4.3 cast into the top of the block just ahead of the bell-housing flange.
'94 Sequential Port Injection introduced this year. The new computer has a PROM that is not removable but can be reprogrammed. A mass airflow sensor was added to work with the map sensor still in use.
'95 A drain tube was added to the distributor to remove condensation buildup. The distributor has a new electrical connector, which is not compatible with the earlier harnesses. The distributor drive was enlarged and will not interchange with '92 - '94 LT1s.
'96 The LT1 picked up 10 extra HP in the F-body cars with the addition of a second catalytic converter. OBD II makes its debut this year. A Crank Position Sensor is added. The LT4 is introduced as an option in the Corvette only and was rated at 330hp. A few of the supertuners offered special editions of the F-body cars with LT4's in them apart from the factory.
'97 The last year for the LT1 and available only in the F-body cars. The new C5 or fifth generation Corvette came equipped with the new third generation small block; an all new, all aluminum 5.7L with no resemblance to the 1st or 2nd generation small blocks.
LS1 Engine
'97 The LS1, GM's generation III all aluminum engine makes it debut in the Corvette rated at 345hp. The LS1 has a deep skirted all aluminum block with 6 bolt mains. This block is 53 lbs. lighter than the LT1's block. The aluminum heads have equally spaced tall, narrow ports, which allows the injector spray to be aimed directly at the back of the intake valve. The composite intake has a low mounted plenum with the 15" long runners curving smoothly over the top of it. The LS1 uses a crank fire distributorless ignition system with one coil per cylinder. Corvette uses an electronic throttle while the V8 F-body uses a conventional throttle cable setup. The new Corvette uses a rear mounted transaxle, which is connected to the engine by a torque, tube, instead of using a conventional transmission.
'98 LS1 is introduced in the redesigned 4th Gen. F-body and is rated at 305hp. The LS1 engines used in the Corvette and the F-body are essentially the same with only minor differences. The Corvette has coil covers, different exhaust manifolds and the alternator mounted high on the left side requiring a remote power steering reservoir. The Corvette LS1 has a slightly different camshaft profile, which allows the engine to meet emissions requirements without using an EGR valve. The F-body has exposed coils and the alternator mounted on the left side below the power steering pump with integral reservoir.
'99 Minor changes in the head and valve cover. Coils are now mounted on a bracket bolted to the valve cover as one unit instead of individually.
Trucks
The new Vortec V8s available this year are versions of the LS1 engine found in Camaros and Corvettes. The truck engines have a cast iron block with aluminum heads and a different intake manifold with the plenum above the runners. The truck LS1 variations are available in 4.8, 5.3 and 6.0 liters. The exhaust manifolds are cast iron and the alternator is mounted high on the left side above the power steering pump with integral reservoir. The A/C compressor is mounted low on the right side like the LS1. The Vortec V8 transmission will bolt up to the Camaro and Corvette engines.
'00 F-bodies got cast exhaust manifolds.
LT1 - Physical Dimensions - 285hp
27 1/2" Long from front of water pump to bell housing flange
24 3/4" Wide measured to the outside of the stock exhaust manifolds
24" Tall from bottom of oil pan to top of throttle body
16" from bottom of oil pan to bottom of exhaust ports
525 lbs. with accessories
Bell-housing Flange
V8's have a different bolt pattern than V6
V8 pattern is the same 1955 - 1997
Flywheel V8
153 tooth 12 3/4" diameter
Transmission 700R4
93 Only, technically called 4L60(not to be confused with 4L60E)
5 wire connector on the left side
Transmission Dimensions 4L60E/700R4 Picture
32 1/2" long 22 1/2" Bell-housing flange to Trans mount
4L60E does not have a kick-down cable
13 Wire connector on right side of Trans
Transmission Dimensions BW T56 Picture
32 1/2" long 25 1/2" Bell-housing flange to Trans mount
Wiring hookups include backup lights, VSS, CAGS, and
Reverse Lockout (none of the wiring hookups are necessary for proper transmission operation)
Shifter is located on the Tailshaft 29" back from front of bell-housing flange
Transmission Gear Ratios
1 2 3 4 5 6
T56 3.36 2.07 1.35 1.00 0.80 0.62 93 Only
T56 2.66 1.78 1.30 1.00 0.74 0.50 94 and later
T5 2.95 1.94 1.34 1.00 0.74
4L60E 3.06 1.63 1.00 0.70
Driveshaft
V8 Shaft is 1 piece V6 is 2 piece
yoke is 1/4" shorter for V6 and automatic
V8 42" long not including yoke
V8 and V6 yokes are 27 spline Same as Powerglide, TH350,and T-5
Rear Axle
65 1/2" wide hub to hub with discs on 4 3/4" pattern
11 1/2" Rotor Single Piston Aluminum Caliper
Ratios available 2.73, 3.23, 3.42
28 Spline Axles
Cars with TCS have a reluctor ring on each axle
Cars without TCS have one reluctor ring on the differential Picture
Rack and Pinion
58 1/2" wide 14" between mounting holes
Brake Booster
9" Diameter
9" from front to the rear mounting points
Master Cylinder
7" long 4 1/2" Tall 2 Brake lines on right side
Aluminum Wheels
Stock 16x8 6 3/4" Backspacing
SS/WS6 17x9 7" Backspacing
Steering Column
Tilt, Cruise, Turn signal, ignition switch
36 1/2" long 3/4" Double D shaft
Cooling Fans
V8 cars have dual 12" fans
V6 cars have a single 16" fan 93 - 96
97 and later V6 got the dual fans like the V8
F-body Parts '98 - '01
LS1 - 305hp
65 lbs. lighter than LT1
26" Bell-housing flange to crank pulley
28" Bell-housing flange to front of water pump
25" Bottom oil pan to top of manifold
12.5" Bell-housing flange to center of motor mount
15" Bottom of oil pan to bottom of exhaust ports
26" Wide to outside of exhaust manifolds
T56 Transmission
Different bolt pattern for bell-housing
5 bolts in same place - 1 moved Picture
Different transmission to bell-housing bolt pattern
Trans input shaft is longer
Now uses a hydraulic throwout bearing instead of
slave cylinder / clutch fork for clutch release
Flywheel 14" 168 Teeth
4L60E Transmission
4L60E has removable bell-housing
Brakes
Front Discs 12"
Dual Piston aluminum calipers
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Zac (The Virgin 97 TA)
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