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The LS1 Gen III 346-cubic-inch 5.7-liter small block V8 was the first LS engine put into production under the hood of the 1997 Corvette. Later the Camaro and GTO also received this powerplant until 2004. There is controversy over if this engine was the replacement for the Gen II small-block 350 engine or if the 5.3 iron block is the new 350 as it is more common and less expensive.

This all new engine  featured an aluminum block and cylinder heads (cathedral port) 10:1:1 compression, a bore of 3.898 inches and a stroke of 3.62 inches. Originally the LS1 made 345 horsepower and 350lb.-ft. of torque.


In 2001 GM decided to bring more power to the table and created the LS6 for the C5 Corvette Z06. A brother to the LS1, the LS6 shares displacement with the LS1 but features a new block casting with a new oil passages and water jacket design for better cooling and oil flow. LS6 engines also had a more aggressive camshaft and better cylinder heads that bumped up compression to 10:5:1.The LS6 had a better flowing intake manifold, as well as other subtle changes such as injectors, valve springs, and exhaust. This made for a higher revving more powerful engine. The Ls6 produced a then impressive 385 horsepower and 385 lb.-ft. of torque, but in 2002 was bumped up to 405. You can find the LS6 in the 2001-2004 Corvette Z06 and first generation (2004-2005) Cadillac CTS-V.


The LS2 364-cubic-inch 6.0-liter engine was the start of the Gen IV engines. Now don’t confuse this with the iron block 6.0 truck engine. This all aluminum performance engine features 10:9:1 compression, a 3.62-inch stroke, a 4-inch bore, and redesigned flat-top pistons. With a 6500-rpm redline this engine produces 400hp, and 400 lb.-ft. of torque.  The LS2 was found in base 2005-2007 C6 Corvette, 2005-2007 CTSV, 2005-2006 GTO, Trail Blazer SS and even the SSR roadster pickup.


The LS3 Gen IV 376 cubic inch 6.2-liter engine is very similar to the LS2 with bigger numbers. With a bore of 4.065 inches, a stroke of 3.622 and L92 style cylinder heads, This one produces 430 horsepower and 424 lb.-ft. Exhaust is one of the biggest variables in the output of the LS3. The factory exhaust manifolds hide horsepower and by adding the Z06 factory exhaust, power numbers increase to 436 horsepower and 428 lb.-ft. of torque in the C6. The LS3 can be found in the 2008-2013 Corvette, 2009 Pontaic G8 GXP, 2014-2016 Chevy SS, and 2010-2015 Camaros equipped with a manual transmission.


Automatic-equipped 5th-gen Camaros have their own version of the LS3 called the L99. The L99 is essentially the same as an LS3 but features active fuel management (AFM, also known as displacement on demand [DOD] or cylinder deactivation), variable valve timing, and a different camshaft. The L99 produces 400hp.


Different from the rest, the LS4 is a transverse -mounted Gen IV 325.1 cubic inch 5.3-liter engine designed for the front-wheel-drive line up. These vehicles include ’05-’08 Grand Prix, ’06-’09 Impala SS, ’06-’07 Monte Carlo SS, and ’08-’09 Buick Lacrosse. Different from the 5.3 truck engine this block is aluminum with LS6 style cylinder heads. Built as compact as possible, the LS4 features a flattened water pump, a different bell housing, a shortened crankshaft, and a redesigned front belt accessories. This engine produces 303 horsepower and 323 lb.-ft. of torque and has active fuel management (AFM). If you were to swap this beast into a mid-engine Pontiac Fiero you wouldn’t be disappointed.


The big legendary LS7 has the classic 427-cubic-inch (7.0-liter) displacement in its aluminum block. The largest  factory LS engine with a bore of 4.125 inches, and 4-inch stroke. With sleeved cylinders, a forged-steel crankshaft, titanium connecting  rods, CNC-ported cylinder heads, 2.20-inch intake valves, and 11:0:1 compression, this engine produces 505 horsepower and 470 lb.-ft. of torque. What is truly amazing is its 7,000rpm redline. The LS7 is a very special kind of crazy and it can be found in 2006-2013 Corvette Zo6, as well as the very unique 2014-2015 Camaro z28. GM also produced an LSX style racing version of the LS7 called the LS7.R , not intended for the public. LS7.R was build specifically for the C5-R/C6-R Corvette in the American Le Mans racing series.


The top dog, the most powerful, the LS9! Similar to the LSA in displacement with more power. Built stronger to accommodate extra horsepower achieved by a larger 2.3-liter supercharger, as well as a more aggressive camshaft. With the addition of an extra 82 horsepower over the LSA, GM added a forged crank, pistons and rods, as well a better air-to-water intercooler to keep it all cool. What is really special about this engine is they are all hand built in Wixom, Michigan. The LS9 debuted in the 2009 specifically for the Corvette ZR1 and is rated at 638 horsepower and 604 lb.-ft of torque.


A monster 376-cubic-inch 6.2-liter engine with a 1.9-liter supercharger. Now you need to understand that this is not just an LS3 with a supercharger, there is more to it than that. Don’t confuse this with the LS9 either.  GM was looking for a more powerful engine for the CTS-V and ZL1 Camaros. It was later decided to build a supercharged version of the LS3 and it has less compression at 9:1:1 to run safer under boost.  GM used a forged crankshaft, oil-spray cooled Hypereutectic pistons, and a hydraulic roller camshaft made to handle boost. There was many other little things that were done to make this engine superior to the LS3, but what your probably wondering is what kind of number it puts down. Well it makes 556 horsepower and 551 lb.-ft. of torque at 9 psi of boost!


The Vortec name has been used a lot in the Chevy engine line-up. It was not until 1999 and newer body GM trucks that these engines  became LS based. You should know that all Vortec truck engines use an iron block. They are built and tuned differently than a true LS engine. Over the years GM has produced so many versions of these engines that it is hard to list all of them, but they are all similar. 4.8, 5.3, 6.0, 6.2, and the often forgotten 8.1 big block are now available. Because trucks are so common in America, there are hundreds of thousands of these engines out there, making them cheap and easy to find parts for. They are also very simple and easy to get reliable horsepower out of making it a very common engine to swap into a project car.


Designed and built for the purpose of racing, LSX engines come as several sizes and options. The LS7.R is the odd one out with an aluminum block. All other LSXs are built with a cast-iron block to withstand over 2000 horsepower with forced induction! You can order your LSX crate engine from Chevrolet Performance, or from any authorized Chevrolet Performance dealer.
Firing order: 1-8-7-2-6-5-4-3

The firing order of the LS1/Vortec V8 has been revised from the Gen I and Gen II engines. This was done to provide more power, less crankshaft rotational stress and better emission and idle qualities.
The camshaft sensor is a 1X pulse sensor which is synchronized to the #1 firing of the engine (Whether or not it is on its firing or exhaust stroke). The reluctor is located on the back of the camshaft. As the reluctor rotates, it interrupts the magnetic field produced by the sensor and the pcm interprets this as a pulse, after the signal is buffered by the internal circuitry of the CMP. The pcm uses this signal in conjunction with the crankshaft sensor (CKP) to determine the crank position and stroke. The pcm monitors this signal for any problems and sets the appropriate DTC (diagnostic trouble code) for loss or degraded signal. The pcm provides the +12V power, ground and signal return for the CMP. A loss of this signal will result in longer starting times. The location of the CMP is on the top rear center of block.
The crankshaft sensor is a 24X pulse sensor that controls ignition coil firing and injector pulse. The 24 tooth reluctor wheel is mounted on the back of the crankshaft. This location is known as the "quiet" deflection zone that minimizes any false signals to the pcm that can be misinterpreted as a fault. As with the CMP, the crankshaft sensor is a magnetic sensor that has the field interrupted by the passing of the teeth on the reluctor. This signal is conditioned by the sensor circuitry so it can be properly used by the pcm. The pcm constantly times the pulse intervals it receives, in conjunction with the CMP to resync the point of the #1 firing stroke. Any changes to the timed intervals at each firing order stroke is read by the pcm as a change in crankshaft velocity. Using the other sensors such a MAP, and TPS, the pcm can determine the changes in crankshaft speed when the engine is accelerating or decelerating, within normal operating conditions, and when the changes are outside the normal parameters, the pcm detects this as a misfire, and the appropriate DTC is set. A loss of this signal will result in a no-start condition. The location of the CKP is on the right hand side above the starter.
The LS1 engines use two knock sensors, the part number is the same for both, but they have two distinct wires to the pcm. The front sensor (KS1) monitors the first 4 cylinders (2 each left and right) while the KS2 monitors the back 4 cylinders. Based on information from the crankshaft sensor, the pcm can detect which cylinder is firing, and each cylinder that is causing a knock situation. The information broken down into a trouble code can tell the technician which cylinder is not receiving fuel, or spark, or is under knock conditions. 
Depending on the type of MAF sensor, the IAT can be either located in the air intake tract or internal to the MAF sensor. The LS6 uses the 85mm MAF that has the IAT integral to the sensor. The IAT (which is also the same as the MAT on older Fuel Injected engines) uses a thermistor which changes resistance based on the air temperature entering the engine. The normal range is from 100K ohms @ -39F, to 70ohms at +266F. At room temperature, this can be from 1500 to 2500 ohms. The pcm supplies a 5V signal to the sensor and monitors the signal on the return. This voltage variation is used by the pcm along with the MAF to determine air density and therefore alter the spark timing accordingly. When the engine is completely cooled down, the scan tool should read a temperature close to the ambient air temperature. When the engine is started and running, the temperature should rise as under hood temperature increases.
The ECT, like the IAT is a thermistor sensor, so it also changes the resistance based on temperature. The same range of resistance (ohms) is used as in the IAT. The pcm also sends a 5V signal to the sensor and monitors the return voltage. When the engine has not been run for several hours, the scan tool should read the IAT and ECT temperatures close to each other. The PCM uses the signal for many of the control systems that affect fuel economy, emissions and idle, so any degraded or loss of signal has a great impact on the engine performance. There are two different ECT sensors. One is a three wire used on very early (1997-98) LS1 engines, where the third wire (usually green) goes directly to the temperature gauge on the instrument panel. The later engines use a two wire sensor and the pcm conditions the signal and a separate signal from the pcm goes to the gauge on the instrument cluster. The ECT location is in the front of driver's side cylinder head.
The MAP sensor is used to measure the amount of pressure change inside the intake manifold. When the vacuum signal is high (idle and deceleration) the voltage is low, while under load and acceleration, when the vacuum signal is low, the voltage from the MAP sensor is high. Just remember that the MAP is inversely proportional to what is measured with a vacuum gauge. This signal is used for the following operations: Altitude compensation Ignition timing control Speed density fuel management default (MAF sensor failure).
The MAF sensor is used to measure the amount of air entering the engine. Idle conditions equal a low air flow, and engine under acceleration indicates a high air flow. The pcm uses the MAF to determine the amount of fuel delivery to the engine. The MAF sensor has a ignition +12V power source, a ground and signal return. The sensor is a hot wire type that the MAF frequency output is a function of how much power it takes to keep the sensing wire at a preset temperature above the ambient temperature. Air flowing across the heated sensing wire cools the wire, and the current increases to maintain this preset temperature. The current increase or decrease is proportional to the air flow. The MAF sensor converts this current into a frequency which is read by the pcm and calculates the air flow in grams per sec (gm/sec). The scanner should display around 9-14 gm/sec, on a fully warmed up engine at idle. The pcm monitors this voltage to determine if the MAF is performing properly and sets the appropriate DTC based on this information. There are two types of MAF sensors. One is he 75mm used on the early LS1 engines, which is a three wire type, and the 85MM version used on the LS6 which has the integral IAT sensor (5 pin sensor).
Like the older engines, the TP (or TPS) is mounted on the throttle body throttle shaft. The sensor is a potentiometer that varies the voltage output based on position (in this case, the angle of the throttle blade). At idle, the output voltage is around 0.6V, and at WOT this voltage is around 4.0V. The pcm sees the signal, along with the CMP, CKP, MAP and MAF to determine if the engine is accelerating or not. This affects many systems, including emission system and fuel calibration control. An erratic or faulty TP sensor will cause erratic engine performance. A DTC will be set depending on the type of fault condition the pcm sees.
The IAC is a pcm controlled stepper motor located in the throttle body, just above the TP sensor. The IAC has pintle that moves back and forth controlling idle speed based on temperature and external loads imposed on it such as the alternator output and AC compressor load. Basically the IAC bypasses air from the outside through a opening just behind the throttle blades. Thus, it acts as a "controlled vacuum leak". The pintle moves away from its seat, to bypass more air and increasing idle speed ( on cold engine start up, or when loads are added that would cause the engine to stall), and moves toward its seat, decreasing the amount of bypass air and lowering idle speed (with engine warming up). The pcm moves the pintle in steps, called "counts". The higher the number, the higher the idle speed and lower counts result in decreased idle speed. The idle speed is determined on: Battery voltage Coolant temperature Engine load Engine rpm ( as determine by the CKP) If the rpm drops below specification with the throttle closed, the pcm will increase the pintle position and calculate this in its memory to prevent stalling. Engines speed is a function of total air intake into the engine (IAC pintle position + throttle angle + bypass air + calibrated vacuum loss through accessories). The controlled idle speed is programmed into the pcm and the correct IAC position is determined for all engine operating parameters. The minimum air rate is set at the factory with a stop screw. This setting allows just enough air to bypass the throttle blade to cause the IAC pintle to be positioned in a calibrated number of steps. NOTE: Do not attempt to adjust idle speed by turning the screw on top of the right side of throttle body, you will damage the IAC motor.
The VSS is an important sensor used by the pcm to determine how fast the vehicle is moving. Located at the back end (tailshaft) of the transmission on either the automatic (4L60E) or manual (T56), this sensor is basically a signal generator that puts out an AC signal that the voltage also increases proportional to how fast the vehicle is moving. The reluctor in the transmission is a 40 tooth wheel. The VSS can be miscalibrated by not using the factory calibrated tire size and gear ratio that was originally installed with the vehicle. Any LS1 retrofit into another vehicle will certainly mean that the pcm will have to be recalibrated for the new tire size and/or gear ratio.
The ignition control for the LS consists of the following systems: One ignition coil for each cylinder Separate IC control circuit for each coil CMP CKP PCM To control the proper firing order of the ignition coil, the pcm bases the information of the following: Engine load based on MAP sensor signal Air intake based on MAF signal input Intake air temperature Crankshaft position Engine speed (RPM) The 24X signal from the CKP not only determines the firing of the ignition coils, but the firing of the injectors as well. The pcm ground the circuit of the IC and this triggers the ignition coil to fire. The timing is not adjustable. Each cylinder has its own coil. The early 1997-98 LS1 engines with perimeter valve cover bolts had the coils mounted directly to the valve cover, later engines that used the center bolt covers has coil mounting brackets.
The O2 sensors on the LS1 are used to monitor the oxygen content in the exhaust gasses. The optimum mixture is to keep to close as a 14.7 to 1 ratio as possible.
The LS1 engines use 4 sensors, 2 on each side, one ahead of the catalytic converters, the other one is called the post catalytic sensor. The first sensor in the stream ahead of the converter is use to trim the fuel calibration to keep the emissions to a minimum, the post-cat sensor is to monitor the efficiency of the converter. The first sensor swings from about .250V to .900V, adjusting from rich to lean detection. The post-cat sensor should have barely any voltage swing at all, if it does, it means the catalytic converter is defective and not cleaning up the exhaust. Any deficiency in any sensor will set a DTC. Most retrofits will not use the post-cat sensor if legal to do so, but the pcm will have to be reprogrammed to ignore the two post cat sensors or a SES light will come on and a code will be thrown. The first two sensors will have to be retained.
August 31, 2019 — Joseph Losco