For years now, enthusiasts have been retrofitting early project cars with LS-series engines and Gen III PCM conversions. The available features (cable or electronic throttle, cruise control, forced induction support, and so on) make the Gen III PCMs highly desirable for nearly any conversion.
The following projects are fine examples of Gen III control systems for small-block engines, turbocharged V-8 and V-6 engines, LT1 engines, and big-block engines.
This Tech Tip is From the Full Book, HOW TO USE AND UPGRADE TO GM GEN III LS-SERIES POWERTRAIN CONTROL SYSTEMS. For a comprehensive guide on this entire subject you can visit this link:
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Project 1: 24x Small-Block Chevy in a 1933 Willys
This is Bill Adam’s 1933 Willys. I met Bill in 2002 when he and his son, Troy, heard there was a guy down the road (me) playing with TPI engines. Bill is a retired toolmaker and fabricated just about everything in this car. He was one of the fi rst in town to install a fuel-injected V-8 engine in a street rod. When I fi rst met Bill, his Willys had an original 1987 5.7L TPI engine with aftermarket wire harness and an ECM (GM# 1227727) from a 1990 Corvette. The Willys ran great, but after seeing some of the newer technology I was playing with, Bill couldn’t leave well enough alone.
GM 4x Vortec Small-Block System
In 2006, Bill and I worked together to upgrade the ECM to a 2002 PCM (GM# 12200411) for single coil and distributor operation using a 1996–2002 ignition system and 2002 Express Van calibration fi le. In hot rodder fashion, the electronics upgrade turned into a heads-up upgrade, including ported aftermarket heads, LT4 hotcam, and TPIS Mini Ram intake manifold. Ultimately the conversion to the GM truck ignition system with this PCM was a failure due to a persistent corrosion problem within (several different styles of) the Vortec distributor.
EFI Connection 24x Small-Block System
Bill was ready to throw in the towel and go back to the TPI ECM. But by then, the prototyping of an EFI Connection24x crankshaft reluctor for small-block engines was nearly complete. So, Bill’s Willys became the first vehicle to receive a 24x conversion (the second was my S10 Wildside pickup).
Removing the high voltage from the Vortec distributor, we only needed the camshaft position signal it provides. Moisture or no moisture within the distributor cap, Bill no longer had to worry about ignition problems related to the Vortec distributor. The 4x Vortec small-block crankshaft reluctor was removed and replaced with the first 24x small-block crankshaft reluctor.
A problem with any crankshaft reluctor installation on an engine that did not originally have a crankshaft reluctor (1995-older) is that General Motors changed the timing cover sealing surface just enough that the 1996- newer plastic Vortec timing covers leak. Although TPIS has since resolved this problem with a machined billet aluminum timing cover, Bill cleaned the face of this 1987 block to apply JB Weld to the trouble areas, ground the new surfaces flat, and then generously applied red RTV sealant to protect against oil leaks.
For the hassle and oil leak risk involved, you are better off buying the TPIS billet-aluminum timing cover and being done with it. TPIS designed their billet-aluminum small-block timing cover for original crankshaft sensor placement, making this beautiful timing cover a direct bolt on for 1996-newer small-block engines as well.
Bill initially chose the 1990 TPI ECM because it offered speed density operation. The 1990–1992 TPI ECMs use a MAP sensor to determine how much fuel to deliver. With tight clearance ahead of the throttle body, and a mechanical fan, a MAF sensor was not possible in this engine bay. The 1996-newer GM fuel management systems use both a MAF and a MAP but the MAF sensor is often eliminated and the PCM is programmed to rely on the MAP sensor for fuel delivery.
Ignition Coil Selection
Bill chose to use LS1 ignition coils (simply because they were available). Some owners unnecessarily get caught up with ignition coil selection. General Motors has used five types of ignition coils (see Chapter 6). Any set of eight ignition coils can be used interchangeably. In fact, among LS-series engines, all ignition coil wire harnesses match every LS-series engine wire harness.
Be aware that the PCM calibration has dwell settings that may need to be adjusted if you use a different set of eight ignition coils. EFI Connection uses the very common GM# 12573190 ignition coils because they fit best on the small-block/LT1 valve covers to allow clearance for oil fill cap, PCV valve, and breather.
DTCs on Startup
Production GM vehicles contain solenoids, relays, sensors, and on-board modules not used in most conversion projects. Upon initial startup of your Gen III PCM conversion, you may notice DTCs that have set related to something that is not used in your vehicle.
Using a base calibration from a 2002 LS1 Camaro with a 4L60-E transmission, the Willys set more than 30 DTCs immediately following the first engine startup. DTCs related to the 4L60-E transmission, emissions equipment, air conditioning, cooling fans, and alternator (that covers just about all of them) can be disabled because the LS1 PCM is not controlling or monitoring this equipment for this vehicle. The mass airflow DTC (P0102) is actually required for DTC processing for speed density operation, but the calibration is set to never illuminate the MIL. It is “normal” for a conversion and clearly explained in EFILive documentation.
VATS Bypass Modules
Almost daily, enthusiasts throw money away by purchasing VATS bypass modules. I quickly found one of these modules on eBay advertising, “Normally it costs between $150 and $300 to have this feature deleted from the PCM. By using our module you accomplish the same function for less and you won’t have to ship your PCM/ ECM to have it reprogrammed.” A VATS bypass module is often purchased during the parts gathering phase of a project and then not used.
The problem with using a bypass module is that the PCM still requires programming to disable other functions specific to the original car. No matter how well-built these modules are, they do nothing more than allow the engine to run so that you can be greeted with an MIL that indicates you need your PCM reprogrammed.
The PCM calibration requires a few changes beyond disabling VATS. Avoid the VATS bypass module and let your tuner disable VATS in the PCM calibration while making other necessary changes.
Bill and I began with a PCM calibration from a vehicle with a 4L60-E transmission so the idle table values would be appropriate for the 700R4 automatic transmission in the car. The PCM immediately sets DTCs related to the 4L60-E transmission. We disabled these within the PCM calibration using EFILive tuning software. This is an appropriate step as they are disabled in a PCM calibration from a manual transmission vehicle. Had General Motors released an LS-series vehicle with the 700R4 transmission, they too would have disabled these DTCs. Bill and I had the foresight to build the engine wire harness to support a 4L60-E transmission.
Adding cruise control to the Willys was an afterthought. The installation was completed; start to finish, over the better part of a Saturday. We scored a used 1998 LS1 Camaro cruise control module on eBay for about $50 and pulled a brake switch from a 1996 LT1 brake pedal assembly that was lying around. The addition of cruise control set us back about $75 and several hours of labor. The Willys required a slight variation on the typical cruise control wiring (see Chapter 14).
First, Bill prototyped a throttle body linkage adapter for the TPI throttle body. This was the most difficult part of the installation because the cruise control cable was designed for an LS1 engine throttle bracket and throttle body. This adapter can be reworked for a better, and cleaner, installation.
Bill identified a stealthy location for the cruise control module beneath the driver’s seat and on the bottom side of the floor. The F-Body cable is plenty long enough to mount the cruise control module out of sight.
While we could have used just about any GM brake switch from a vehicle with cruise control, we had a 1996 F-Body brake switch that fit nicely within the tight space of the dash. We tapped into the stop lamp circuit and TCC brake signal circuit to satisfy the cruise control module’s brake switch signal requirements. Bill used a steering column from an early GM vehicle with cruise control. The multifunction lever (turn signal and cruise control switch lever) only had the set/coast feature, so we wired the cruise ON/OFF to switched 12V ignition, ignoring the resume/accel feature.
The cruise control module requires a 4,000-pulse-permile VSS signal, so we looked to the LS1 PCM. The PCM’s primary VSS output was already being used for the speedometer (red connector, cavity 50, green/white wire), so we used the PCM’s secondary VSS output wire at the red connector, cavity 49. The final step was to change the PCM’s secondary VSS output signal to 4,000 pulses per mile using EFILive tuning software.
Bill’s 1933 Willys is a fine example of a Gen III PCM bringing modern fuel injection, tuning, and additional nice-to-have features (such as cruise control) to an early street rod. The only improvement left for the Willys is a 4L60-E transmission upgrade. The 700R4 has seen better days and Bill is already looking forward to the drivability improvements after a 4L60-E installation.
Project 2: Twin-Turbo Small-Block Chevy in a 1998 GMC Truck
Jeff Jones is the owner of a unique 1998 GMC Sierra. Although his professional automotive day job is as a Lexus technician, his automotive hobby includes GM engine performance. Looking for more performance from his 5.0L Vortec engine, he went to the salvage yard to source two turbos for a little added “boost.” The plastic Vortec intake manifold was problematic for several reasons, including the inability to properly size fuel injectors for the additional demands of using two turbos. A Ram Jet 350 intake manifold was a direct fi t to the 5.0L Vortec engine and allowed for external fuel injectors, a forward-facing throttle body, and better airfl ow than the original intake manifold. The next issue was to address the limitations of the 1996–2000 Vortec “black box” PCM that General Motors designed to power the truck.
Jeff’s twin-turbo build required a better PCM than was in the car. The truck’s original black box PCM is not capable of reading boost or MAP sensor values above 105 kpa. He dismissed aftermarket ECUs with a hunch that a newer GM PCM may allow for the rest of his truck (gauges, transmission, air conditioning, etc.) to remain fully functional. Jeff knew that the Vortec 5.0L engine in his GMC was used through 2002 in the Chevy Express Van and that the 2002 Express Van used the same PCM (GM# 12200411) that is used with 2002 LS-series engines.
With the buzz on Internet message forums discussing LS1 vehicles being tuned for forced induction while using the original GM PCM, he had a promising direction forward. Thanks to EFILive, the GM PCM can be loaded with a custom OS to fully support forced induction.
Repinning the Engine Wire Harness
While wiring in a new PCM may seem like an enormous task, General Motors has made this rather easy by using the same connector terminals for 1996–2000 truck PCMs and the 2001–2002 GM# 12200411 PCM. The connector family and series are Delphi Micro- Pack 100W. Although the connectors are different, the terminals are interchangeable. All that is required is a terminal removal tool (or your fingernail), wiring diagrams, and a little time.
Jeff has been helping truck owners repin their black box PCMs for the newer PCM (GM# 12200411) for years through a well-documented repin guide. The Gen III PCMs require two 80-cavity Micro-Pack 100W connectors; each connector uses two colored and indexed retainers. This PCM requires two blue retainers and two red retainers.
The 1996–2000 PCM is located on the driver-side fender in the engine bay. The engine wire harness is easily accessed and serviceable when disconnected from the PCM. The Vortec black box PCM uses four (sometimes fi ve) connectors.
The new PCM fi ts nicely in the location of the original black box PCM. The engine wire harness is repinned, one wire at a time, with the two 80-cavity LS-series PCM connectors. If you take your time, you can make the harness rework of the new PCM look as if it has always been there.
Gear Select Switch
In an automatic transmission vehicle, the PCM needs to know when the transmission is in park or neutral (P/N), or in gear. Manual transmission vehicles do not have a gear select switch.
In 1996–2000 GM trucks, the automatic transmissions have a gear select switch mounted on the side of the transmission case. The four-gear select switch wires are routed to the instrument cluster. Jeff chose to splice into these four wires from inside the truck to avoid corrosion and weather-related issues that can occur if the splices are made under the truck.
Because the first use of this PCM (GM# 12200411) in this 1998 GMC truck was with a calibration from a 2002 Express Van (4x crankshaft reluctor), the calibration’s gear select switch type was already set to PRNDL (because the 2002 Express Van has a gear select switch on the side of the transmission).
After the 24x conversion, Jeff began with a 2002 LS1Camaro/Firebird calibration and had to change the gear select switch type from P/N Switch to PRNDL. The LS1 Camaro and Firebird do not use a gear select switch on the side of the transmission since a P/N switch is in the center console that applies a single ground signal to the PCM (blue connector, pin 34) to indicate P/N.
An alternative after a 24x conversion is to begin with a calibration from an LS-series truck because the calibration is already set to the gear select switch type of PRNDL, as LS-series trucks have a gear select switch mounted on the side of the transmission case.
Dual electric fans from a 2002 LS1 Firebird were installed after the PCM conversion. The Gen III PCMs can control up to two electric fans. The PCM does not supply power and ground for the fans, it supplies the ground trigger to the fan relays. The fan relays supply the power and ground for the fans. A quick trip to the local salvage yard sourced three relays and connectors for the wiring involved. By using the three relays, as is done in the LS1 Camaro/Firebird, the PCM can command low-/ high-speed operation of the two electric fans. (See Chapter 9 for more about electric fan operation.)
After the dual electric fan installation, Jeff added the Camaro/Firebird three-wire A/C pressure sensor for proper operation of the electric fans when the A/C was on. Now the cooling fans cycle properly to meet the demands of the A/C system. (See Chapter 11 for more information about A/C operation.)
The LS1 Firebird electric fans are mounted neatly behind the radiator.
4x Crankshaft Signal: Single Coil and Distributor
On a Vortec small-block engine, the CKP sensor signal output is 4x and CMP sensor signal output is 1x. The ignition system for all Vortec small-block engines is single coil and distributor. Although the ignition system remained the same, the new PCM brought the benefits of forced induction support, electric fan operation, engine speed beyond 5,800 rpm, and popular tuning software support. After all, locating a chassis dyno facility that is fluent with the LS-series PCMs is rather easy.
24x Crankshaft Signal: Coil-Per-Cylinder Ignition
Several years after the PCM conversion, this 5.0L Vortec engine received an EFI Connection 24x crankshaft reluctor and new crankshaft sensor. Having already repinned the engine wire harness at the PCM, all that had to be done was add 10 ignition coil control wires and use the 12V switched ignition and ground wires from the original ignition module and coil wiring to power the eight LS ignition coils. Rather than mount the ignition coils on the valve covers, a bracket was made to mount them on the firewall.
Jeff has been gathering parts for a swap from cable throttle to electronic throttle. With a 24x crankshaft reluctor in the engine, he may install a 2003-newer Gen III PCM. Electronic throttle equipment is plentiful in 2003-newer LS-series trucks, but he will run into a snag with electric fan operation while the A/C is on because the 2003- newer GM trucks eliminated the 12V A/C request to the PCM.
A workaround is to activate the electric fan relays from the A/C control switch (and disable the resulting electric fan DTCs in the PCM calibration).
To keep PCM-controlled electric fan operation while the A/C is on, either LS1/LS6 Corvette electronic throttle equipment or 1999–2002 GM truck electronic throttle equipment may be used while retaining the PCM (GM# 12200411). (See Chapter 8 for more information about electronic throttle equipment.)
Regardless of his choice, the Ram Jet 350 intake manifold accepts any Gen III throttle body and the cruise control switches in the steering column multifunction lever integrate seamlessly with any Gen III TAC module. With several electronic pedal assembly options, a custom mount and possible alterations to the pedal length may be required to properly locate the accelerator pedal pad.
The PCM swap was the foundation for every modification that has been done to Jeff’s truck. He considers this project and PCM-related upgrades to be one of the most educational and fun things he has ever done. From Internet message forums, Jeff has learned from people around the world with this same passion, and they shared information and creative ideas. Through this DIY project, he has created unexpected friendships that help to keep this passion alive.
I met Jeff at his home while en route to the 2009 Car Craft Summer Nationals event. Sharing his genuine passion for GM engine management fuels my flame for this exciting hobby. Don’t let the Lexus technician title fool you; Jeff represents GM performance through and through!
Project 3: Turbo 4.3L V-6 3x Conversion
Fuel injection for GM’s popular 4.3L V-6 engines was introduced in the 1980s with a TBI unit on the top of the engine’s intake manifold. These TBI units use two fuel injectors to distribute fuel in a central location within the intake manifold. Engine vacuum pulls the air/ fuel mixture into each cylinder for combustion. These early 4.3L engines are controlled by ECMs designed to be used with the two TBI injectors.
The 1991 GMC Syclone received the first 4.3L V-6 engine to feature multi-port injection; it had six individual fuel injectors for fuel delivery into each cylinder head intake runner. This improved method of fuel delivery required a new ECM with internal drivers capable of operating the six high-impedance fuel injectors. Although six fuel injectors are used, the ECM has only two injector drivers to run a batch fi re mode (one bank of three injectors at a time). Sequential fi re injection was not available for the GMC Syclone or GMC Typhoon.
The 1991 GMC Syclone and 1992–1993 GMC Typhoon do not share the ECM or ignition system with any other 4.3L V-6 engine application. The unique requirement for forced induction, a turbocharger fitted on these 4.3L V-6 engines, was an ECM and calibration capable of controlling the engine’s six fuel injectors and spark advance while under boost (2-bar) conditions. The typical 4.3L V-6 ECM of those days was not designed to be used with this turbocharged engine.
With upgraded engine components (and more boost), 4.3L V-6 owners have gone to the aftermarket to install new (and expensive) fuel management systems for greater tuneability and control of their powerplant. Unfortunately, aftermarket systems may lack support for the vehicle’s gauges, cruise control, and transmission torque converter lockup control, thus requiring additional aftermarket solutions that only add to the expense of an upgraded fuel management and ignition system.
Gen III PCM
Here is great news for the 4.3L V-6: General Motors has inexpensive production parts available to use the Gen III PCM with any 4.3L V-6 engine. The 2001–2002 PCM (GM# 12200411) was used with both LS-series V-8 engines and the 4.3L V-6 engines found in S-series trucks and vans. These engines are fi tted with the 1996-newer 3x crankshaft reluctor and single coil and distributor Vortec ignition system. The same tuning software, such as EFILive, is used with this PCM, regardless of V-6 or V-8 calibration. Other tuning benefi ts, such as custom operating systems for 2- and 3-bar MAP support, are conveniently included.
GM’s 3x crankshaft reluctor for Vortec V-6 engines is shaped to allow clearance for only a single roller timing chain. Production GM engines use a single roller timing chain, so if upgrading to a double roller timing chain, EFI Connection’s 3x billet-steel crankshaft reluctor is required for reluctor-to-timing chain clearance.
The 1996 4.3L Vortec V-6 engine was updated with an upper balance shaft. The changes to the face of the engine block required a new, and taller, timing cover. This timing cover made provision for the CKP sensor that is used to receive an engine position signal from the 3x crankshaft reluctor.
Those with an early 4.3L V-6 are not able to use the GM plastic Vortec timing cover because the upper portion of the cover does not seal to the early engine block. Fortunately the early 4.3L V-6 engines share the same timing cover as Gen I small-block engines. For CKP sensor provision for early 4.3L engines, the TPIS billet-aluminum small-block timing cover provides the best fi tment while properly sealing to the face of the engine block.
The GM# 12200411 PCM controls the six fuel injectors in sequential fi re (not batch fi re) mode. This means individual control of the fuel injectors. With the requirement of six fuel injectors, this newer PCM cannot be used with TBI units.
Early 4.3L TBI engines must receive a multi-port injection intake manifold upgrade so that six fuel injectors may be used. This requirement may be fi lled by sourcing a used Syclone or Typhoon intake manifold, aftermarket or custom manifold, or upgrading to Vortec cylinder heads and a production GM intake manifold. An attractive option for 4.3L engines using Vortec cylinder heads is the 4.3L marine manifold because it features external fuel injectors and a Gen III 3-bolt type throttle body.
The Syclone/Typhoon, Vortec truck, and LS-series throttle body TPS and IAC engines are directly compatible with this PCM. In fact, so are the ECT, IAT, and MAP sensors used with these V-6 and V-8 engines. The only remaining sensors to add are knock sensors, heated O2 sensors, optional MAF sensor, CMP sensor, and CKP sensor.
Single Coil and Distributor Ignition
The GM# 12200411 PCM was only used with the 4.3L V-6 engines in a single coil and distributor configuration. General Motors wrote the calibration software to expect 3x crankshaft and 1x camshaft signals for engine operation. This PCM uses the 3x crankshaft signal (and other engine sensor inputs) to control the ignition spark advance through the Vortec ignition module and single coil.
It may seem that by providing a higher-resolution crankshaft signal (such as a 24x LS-series crankshaft signal), the PCM controls one coil per cylinder but it simply does not work that way. GM’s 24x encoded signal is mapped for V-8 engines only. Had General Motors released a PCM calibration that supported coil-per-cylinder ignition for the V-6, an appropriate crankshaft reluctor with increased tooth count (higher resolution) could be installed to eliminate single coil and distributor ignition. What General Motors has provided, however, is no disappointment.
Tuning software, such as EFILive, delivers the same tuning benefi ts that sell us on the use of the Gen III PCM for LS-series engines as it does for V-6 engines. Through the same calibration tables and parameters, the same tuning software and hardware, and the same tuning techniques, this PCM is a fantastic engine controller for any 4.3L V-6 engine.
Vortec cylinder heads are plentiful in the boneyards and offer excellent performance gain compared to the early 4.3L cylinder heads. The lower Syclone and Typhoon intake manifold may be modified to accommodate the raised intake runners of the Vortec cylinder heads. Rather than machine the Syclone or Typhoon intake manifold for the Vortec head bolt pattern, the Vortec heads can be drilled for the early 4.3L V-6 bolt pattern to create a better seal and clamping force.
3x Crankshaft Reluctor
The 3x crankshaft reluctor installs on the crankshaft and is firmly held in place between the crankshaft timing sprocket and crankshaft balancer. GM’s 3x crankshaft reluctor fully seats against the crankshaft timing sprocket only when using a single roller timing chain. Double roller timing chain installations require EFI Connection’s 3x crankshaft reluctor.
Vortec Distributor Assembly
The 1996-newer 4.3L V-6 distributor assembly installs in the traditional distributor location and is used to provide a 1x camshaft signal to the PCM. The PCM uses this camshaft signal to determine intake or exhaust stroke for any given cylinder during engine operation.
Project 4: 24x LT1 Conversion to Eliminate Optispark in an F-Body
The 24x LT1 conversion is considered one of the best upgrades for a 1993–1997 F-Body. LT1 owners are finding limited tuning support and must fight ignition system problems due to the front-mount Optispark distributor. EFI Connection’s well-designed 24x conversion hardware brings the LS1 PCM to the LT1 car in similar fashion to how General Motors would have done it. This owner’s intent was to get the most power possible out of the engine and eliminate an ignition hiccup experienced in the upper RPM. This 24x conversion accomplished both goals and has forever eliminated woes associated with the LT1 Optispark distributor.
Step 1: Retrieve LT1 PCM Calibration
Because this car has been previously tuned, we pull the calibration fi le out of the LT1 PCM using the C.A.T.S. OBD-II tuner. The calibration will be used later as a reference while making a starter calibration fi le for the LS1 PCM using EFILive software.
Step 2: Inspect Engine Bay Prior to Disassembly
Here is the engine bay before disassembly. The LT1 PCM and engine wire harness will be removed and replaced with an LS1 PCM and new 24x LT1 wire harness from EFI Connection.
Step 3: Drain Coolantt
The 24x conversion requires that the timing cover be removed from the engine. The water pump must be removed before the timing cover, so the coolant is drained.
Step 4: Remove Balancer
A proper puller, such as this Kent Moore J-39046 tool, is used to remove the balancer from the crankshaft hub. Without this tool, there may be difficulty pulling the balancer due to the tight space between the engine and electric fan assembly.
Step 5: Note LT1 Hub Configuration
The LT1 engine has a separate crankshaft balancer and hub. (Other engines have a one-piece balancer.) The bolt pattern of the Camaro/Firebird hub is not the same as other LT1 engines. The Kent-Moore J-39046 provides alternate through-hole configurations to remove any LT1 crankshaft hub.
Step 6: Remove Water Pump
The water pump is removed to allow for timing cover removal. This includes removing the hoses, ECT sensor harness connector, and six attaching bolts. The water pump is held in place by two locating pins in the engine block near the top of the front timing cover. The Water pump housing is gently pried from the two locating pins to remove the water pump.
Step 7: Remove Ignition Module and Coil
The ignition module and coil mounted on front of bank 1 cylinder head is removed. It is not used after the 24x conversion. This car also had its aftermarket ignition controller removed. An aftermarket ignition module is not needed for any 24x conversion.
Step 8: Remove Optispark Attaching Bolts
The three Optispark attaching bolts are removed. Two are easily reached from above and one is easily reached from below. The Optispark is then removed from the timing cover.
Step 9: Remove Optispark
With the removal of nine spark plug wires and vacuum/vent hose the Optispark distributor is removed from the front of the engine. The Optispark timing cover seal and three attaching bolts will be used with the installation of the CMP sensor housing.
Step 10: Use Hub Removal Tool and Bar
GM service shops use the Kent Moore J-39046 hub removal and installation tool to service the variety of LT1 crankshaft hubs. This tool makes removal and installation of an LT1 hub safe and easy. (Although the tool is expensive, you can do yourself a big favor by buying and reselling it on ebay.)
A hub removal bar is inserted into the front of the crankshaft. The removal bar bottoms out in the crankshaft bolt hole and will be used with the removal tool to pull the crankshaft hub from the snout of the crankshaft.
The hub removal tool flange is installed on the hub with three attaching bolts. The flange has alternate through-hole patterns forthe removal of other LT1 crankshaft hubs (such as Corvette and Caprice/ Impala). The front nut is fi rst lubricated with antiseize compound to prevent galling of the threads. With the nut threaded into the removal tool fl ange, it is tightened to apply pressureagainst the hub removal bar. As the nut is turned, the crankshaft hub is pulled away and removed from the snout of the crankshaft.
Step 11: Loosen Oil Pan
Before the timing cover can be removed, the front of the oil pan must drop. All but the rear two oil pan fasteners are removed. As the rear two oil pan nuts are loosened, the front of the oil pan drops to allow the timing cover to be removed.
Step 12: Remove Timing Cover
With the front of the oil pan dropped, the timing cover is carefully pried from the engine. The 1996– 1997 4x crankshaft reluctor was used by the PCM for misfi re detection. It will be removed and replaced with EFI Connection’s 24x crankshaft reluctor.
Step 13: Test Fit 1x Camshaft Reluctor
The Gen III PCM requires a 1x camshaft signal so that the stroke (intake or exhaust is known for any given cylinder during engine operation. This 1x camshaft reluctor is installed in front of the camshaft timing sprocket using three new button-head bolts. The 1995–1997 LT1 engines have a long dowel pin in the front of the camshaft that is used to drive the Optispark distributor. For 1995–1997 camshafts only, the pin must be replaced (if possible), tapped in (if possible), or cut near flush with the surface of the 1x camshaft reluctor. No other camshaft requires modification to the camshaft pin. Some aftermarket camshafts use a slightly oversized pin that requires very light reaming or drilling of the 1x camshaft reluctor dowel pin hole. A test fi t of the camshaft reluctor should allow it to fully seat against the face of the camshaft timing sprocket and the camshaft dowel pin near-flush with the reluctor flange.
Step 14: Attach 1x Camshaft Reluctor Bolts
The 1x camshaft reluctor is installed using the three new button-head bolts, which have received removable liquid thread locker. Assembly requires each bolt to be turned the distance of several threads at a time in a clockwise or counter-clockwise order to avoid binding the camshaft reluctor with the attaching bolts.
Step 15: Install 1x Camshaft Reluctor
With the attaching bolts finger tight, they are then torqued to GM’s recommended 18 ft-lbs. If the bolts need to be removed for future timing set or camshaft service, they should be removed several turns at a time in a clockwise or counter-clockwise order. Removal with an impact gun pushes the head of the bolts through the top of the camshaft reluctor, causing permanent damage to the reluctor.
Step 16: Install 24x Crankshaft Reluctor
EFI Connection’s 24x crankshaft reluctor is installed. Notice the crankshaft woodruff key is flush with the face of the 24x crankshaft reluctor. LT1 hubs do not have a keyway, so the key must be flush with the reluctor. The 1992–1995 LT1 engines require the removal of the crankshaft timing sprocket, removal of the woodruff key, and installation of the 1996–1997 LT1 crankshaft key. The OBD-I LT1 engines do not have a crankshaft reluctor, so the early woodruff key does not engage with the 24x crankshaft reluctor.
Step 17: Install Timing Cover
The timing cover is installed. An aluminum water pump seal tool was used to prevent damage to the water pump drive seal. This was a $25 tool from eBay.
Step 18: Install Crankshaft Hub
The crankshaft hub is ready for installation. The 1992–1995 (OBD-I) LT1 engines do not have a 4x crankshaft reluctor. These early hubs are longer than the1996–1997 (OBD-II) LT1 hubs used with engines that do have a 4x crankshaft reluctor. For this reason, when installing the 24x crankshaft reluctor in a 1992– 1995 LT1 engine, the hub must either be shortened by the thickness of the 24x crankshaft reluctor or a 1996–N1997 hub must be used.
Step 19: Use Installation Tool
The Kent Moore J-39046 installation tool is used to install the crankshaft hub. The installation screw is first threaded into the crankshaft, then loosely set onto the snout of the crankshaft. An installation thrust bearing and forcing nut are then installed onto the installation screw.
Step 20: Push Hub onto Crankshaft
Using a wrench, the installation forcing nut is tightened against the installation thrust bearing. As the forcing nut is tightened, the hub is pulled onto the crankshaft. The crankshaft hub bolt is torqued to GM’s recommended 75 ft-lbs.
Step 21: Fully Seat Crankshaft Hub
Proper installation of the crankshaft hub is very important. If the crankshaft hub is not fully seated, the crankshaft reluctor wheel is loose and the engine runs very poorly while intermittently stalling as the CKP sensor loses signal from a wobbly crankshaft reluctor wheel.
Step 22: Install Camshaft Sensor Housing
EFI Connection’s camshaft sensor housing is installed in the location where the Optispark distributor used to be, using the same three Optispark attaching bolts through the timing cover. A Gen IV CKP sensor is used to get the 50-percent duty-cycle signal from the 1x camshaft reluctor installed on the front of the camshaft timing sprocket.
Step 23: Remove Kick Panel Trim
Prior to removing the engine wire harness from the engine bay, four connections must be disconnected in the passenger-side kick-panel area. The kick panel trim is carefully lifted up and out of the car after removing the Phillips-head attaching screws.
Step 24: Disconnect Dash Harness Connectors
Four dash harness connectors must be disconnected. The 10-cavity white (connector C220), 10-cavity blue (connector C230), 4-cavity black (connector C210), and A/C evaporator housing temperature sensor connectors are disconnected. The LS1 PCM does not use the A/C evaporator housing temperature sensor for A/C operation. The LS1 PCM properly, and seamlessly, controls the A/C system in the LT1 car.
Step 25: Remove Engine Wire Harness
The LT1 engine wire harness is removed. Removal is a bit tedious and needs some patience and care. The front of the car must be elevated to remove harness connections near the bottom of the engine and at the transmission.
Step 26: Disconnect HVAC Vacuum Line
The HVAC temperature control vacuum hose must be disconnected. This hose is taped within the LT1 engine wire harness to supply engine vacuum to the HVAC controls inside the vehicle.
Step 27: Prep Ignition Coil Bracket for Installation
The ignition coil bracket assemblies are installed on each valve cover by removing the four center bolts. The bolts are replaced with new, longer bolts and spacers between the ignition coil bracket and valve cover. The coil bracket is carefully fitted to the valve cover so that the aluminum spacers do not slide off the attaching bolts.
Step 28: Install Ignition Coil Bracket
After tightening the four coil bracket bolts, the ignition coils are installed onto the coil bracket assembly. The ignition coil harness is then connected to each of the four coils on each bracket. The center, seven-cavity connector is the same as found with any GM LS-series ignition coil harness; allowing compatibility with any new or reworked LS-type engine harness.
Step 29: Inspect Engine Wire Harness
The original LT1 engine wire harness (top) will no longer be used. The new EFI plug-and play engine wire harness (bottom) is ready for installation. It contains several extra wires bundled beyond the fi rewall grommet that are unique to this car’s installation. These wires are for nitrous installation and conversion from a 4L60-E automatic transmission to a T56 manual transmission.
Step 30: Inspect 24x Conversion
After installing the water pump and refilling the coolant, this 1997 Trans Am is now fully equipped for LS1 PCM use. EFI Connection’s 24x hardware and new plug-and-play wire harness provide a factory-look installation. Many who see the vehicle at local car show events do not notice the LS1 PCM upgrade.
Step 31: Transport to Dyno
This 1997 Trans Am was trailered to Smokey’s Dyno & Performance in Akron, Ohio, for final tuning. Since this photo was taken, Smokey’s Dyno & Performance has been relocated to a new, and larger, facility in the same area.
Step 32:Calibrate PCM
The previous LT1 PCM calibration is used only as a reference while a starter calibration file is creatd for the LS1 PCM using EFILive tuning software. This starter calibration file allows the engine to run well enough to begin the custom tuning process while the car is run on the dyno.
Step 33:Dyno Tun
The car is properly strapped to the chassis dyno. An ideal location for the wide-band O2 sensor is in the exhaust and close to the engine. When a third O2 sensor bung is not available in the exhaust, the wide-band sensor is often installed in the tailpipe (as here). By using the wide-band sensor’s air/fuel mixture readings, adjustment are made to the PCM calibration.
This car was tuned previously with the same engine configuration. The 24x conversion yielded an increase of roughly 10 hp and 10 lb-fts of torque. The final results are an impressive 420 hp and 402 lb-fts of torque.
Project 5: Big-Block Ram Jet 502 24x Conversion
Without question, GM’s Ram Jet 502 crate engine is designed to impress. This engine is big, beautiful, and boasts an impressive 502 hp and 565 lb-fts of torque! What it lacks is modern features including OBD-II diagnostics, distributor-less ignition, electronic automatic transmission support, cruise control, electric fan control, and popular tuning support from a tuning package such as EFILive.
The Ram Jet 502 shortcomings can be summed up in one word: MEFI. The marine electronic fuel injection (MEFI) ECM bundled with this engine had marine use in mind and not the comforts of on-road use.
Let’s take a look at what is required to use the Gen III PCM with the Ram Jet 502.
Step 1: Remove Valve Cover
A 24x conversion on this engine requires eight ignition coils. For convenience, LS1 ignition coils can be mounted on top of the valve covers using two valve covers (GM# 12554353). Although the Gen VII 8.1L valve cover looks similar, the bolt pattern and height is incorrect for Gen VI big-block engines.
Step 2: Remove Distributor and Valve Covers
The small-cap HEI distributor, plug wires, valve covers, and valve cover gaskets are not used.
Step 3: Install Valve Covers and Ignition Coils
These valve covers require LS1/LS6 ignition coils (GM# 12558948). Any other ignition coil does not fit the mounting holes.
Notice how the layout of ignition coils matches the angle of the spark plug configuration. Bank 1 ignition coils are toward the rear of the engine; bank 2 ignition coils are toward the front of the engine. This is the best layout for the angled spark plugs.
Step 4: Remove Old Distributor
The early small-cap HEI distributor is replaced with a 1996–2002 Vortec distributor assembly. Hold on to the distributor clamp because it is required with the new distributor.
Step 5: Choose New Distributor
The small-cap HEI distributor (left) bundled with the Ram Jet 502 crate engine is for use with 1985–1992 TPI-type ECMs and MEFI-series ECMs. This distributor is replaced with a 1996–2002 Vortec distributor (right) for the purpose of driving the oil pump and providing a camshaft signal to the Gen III PCM. This Vortec distributor is offered through the aftermarket. It has an improved design as it is made of cast aluminum rather than the plastic GM equivalent. The Vortec distributor cap is replaced with EFI Connection’s cast-aluminum cap to eliminate spark plug wire provision.
Step 6: Install Distributor
The Vortec distributor uses a CMP sensor to output a 1x signal (50-percent duty cycle) to the PCM for the purpose of indicating the stroke for each cylinder while the engine is running. In fact, this is the only electronic purpose of this distributor.
Step 7: Install Aluminum Distributor Cap
Any 1996-newer Vortec 4.3, 5.0, 5.7, or 7.4L distributor assembly may be used to accomplish the Gen III PCM requirement of a 1x camshaft signal. EFI Connection’s cast-aluminum cap is then installed to eliminate spark plug wire provision and provide a clean look.
Step 8: Remove Balancer
The balancer must be removed to remove the timing cover. A quality removal tool is inexpensive, and preferred to avoid damage to the crank snout and/or balancer.
Step 9: Remove Oil Pan Bolts
With the balancer removed, the front of the oil pan must drop before the timing cover can be removed. All but the rear two oil pan bolts are removed. The rear two oil pan bolts are loosened to allow the front of the oil pan to drop.
Step 10: Remove Timing Cover
With the balancer and timing cover removed, the crank is nearly ready to receive the 24x crankshaft reluctor.
Step 11: Inspect Timing Set
For any big-block 24x conversion, this is the point of the installation that becomes critical. Not all GM big-block timing sets are the same. More specifi cally, not all Gen VI big-block engine timing sets are the same. With varying crankshaft timing sprocket thicknesses, the 24x crankshaft reluctor may be located too far forward of the CKP sensor, causing a no-start condition and wear on the timing cover as the crankshaft reluctor binds with the timing cover during engine rotation.
Step 12: Remove Crankshaft Timing Sprocket
This Gen VI timing cover is production equipment from a 1996-newer Gen VI 7.4L engine. That engine has a 4x crankshaft reluctor. The placement of that 4x crankshaft reluctor is determined by the thickness of the crankshaft timing sprocket used with the engine. The timing cover sensor hole is located in a position where the CKP sensor gets a signal from the crankshaft reluctor. Because we are using a Gen VI 7.4L timing cover with the Ram Jet 502, we must consider the difference in crankshaft timing sprocket thickness between the 7.4L crankshaft timing sprocket and Ram Jet 502 timing sprocket. For this reason, the crankshaft timing sprocket is removed.
Step 13: Mill Timing Sprocket to Fit
The Ram Jet 502 crankshaft timing sprocket (left) is noticeably different than the Gen VI 7.4L crankshaft timing sprocket (right). It appears that the Ram Jet 502 sprocket seats closer to the engine. In reality, the sprocket is seated quite differently on the 502 crankshaft. Measurements of the 7.4L and Ram Jet 502 camshaft timing sprockets confirm that the location of the sprocket teeth is the same on the two engines. What varies is the distance from the front of the sprocket teeth to the seating surface of the crankshaft reluctor. The 7.4L sprocket measures .143 inch from the sprocket teeth to the front of the sprocket. The Ram Jet 502 sprocket measures .203 inch from the sprocket teeth to the front of the sprocket. The .060-inch difference is milled from the front of the Ram Jet 502 crankshaft sprocket before installation so that the crankshaft reluctor is within the CKP sensor range and does not bind against the timing cover.
Step 14: Install Crankshaft Reluctor
With the crankshaft timing sprocket and timing chain reinstalled, the 24x crankshaft reluctor simply slides on the front of the crank snout and is seated against the crankshaft timing sprocket.
Step 15: Choose Timing Cover
The MEFI system does not use a CKP sensor, so the timing cover is cast without the sensor hole.
The 502 engine’s timing cover (right) was replaced by a factory 7.4L (left) timing cover with a provision for the CKP sensor, which is easier than modifying the 502 cover from the crate engine.
Step 16: Install Timing Cover
The Gen VI 7.4L timing cover is installed and the oil pan is ready for reassembly.
Step 17: Modify Balancer
For proper crankshaft pulley alignment (so that the belt rides in-line with the rest of the front engine accessories), the snout of the balancer must be machined. For this installation, the 24x crankshaft reluctor that was installed measures .190-inch in thickness, so .130 inch is removed from the snout of the balancer before installation.
Step 18: Install Balancer
The balancer is installed using a proper installation tool. A mallet should never be used to force the balancer onto the crankshaft. A proper installation tool is inexpensive and avoids damage to the engine and balancer.
Step 19: Reassemble Front of Engine
This Ram Jet 502 is now equipped with the 24x crankshaft signal requirement of the Gen III PCM. There is no need for an external crankshaft reluctor and sensor solution when an internal solution is available.
Step 20: Remove Throttle Body
With the throttle body removed, the two bores in the front of the intake plenum can be seen. A throttle body upgrade requires modification to the front of the plenum for throttle blade clearance.
Step 21: Remove Throttle Body (continued)
EFI Connection’s electronic mono blade throttle body (top) is designed for the bolt pattern of the Ram Jet 502 (and TPI/LT1) intake plenum. The mono-blade throttle body flows nearly 1,250 cfm of air, making the most of the 502’s breathing ability.
The original twin 48-mm throttle body (bottom) flowing approximately 670 cfm has plenty of room for additional horsepower and torque with a throttle body upgrade. TPIS offers a cable-driven, mono-blade throttle body for the Ram Jet 502.
Step 22: Inspect Complete Conversion
This Ram Jet 502 is now ready for Gen III PCM control. This particular configuration, with an electronic mono-blade throttle body, supports cruise control through an LS1 Corvette TAC module. This engine can just as easily be configured for use with a cable throttle body and an external, cable-driven, cruise control module (see Chapter 12).
Written by Mike Noonan and Posted with Permission of CarTechBooks