If there is one great aspect to General Motor’s small-block V-8s, it is that they have a lot in common. This is especially true with the Gen III V-8. It means parts off the Z06 Corvette engine, the LS6, fit on 6.0-liter Gen III truck engines without a lot of work. So, this is the chapter that will tell you what other quality original equipment manufacturer (OEM) parts can be swapped to different vehicles and provide real performance. Not only does this chapter show you what factory performance parts to use and how to swap them onto your base engine for a power increase, there are many tips and tricks on how to massage a little more performance out of these same pieces for little or no money.
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The components discussed here are arranged in order from the foundation components up to the small details. They include engine blocks, cylinder heads, intakes, camshafts, throttle bodies, MAF sensors, and airboxes. The airbox, MAF, and throttle body are all simple remove and replace (R and R) jobs on many vehicle platforms. The block, cylinder heads, camshaft, and intake require the engine to be removed from the vehicle. But, as you’ll see elsewhere in this book, the Gen III V-8 engine is by far the easiest to disassemble and reassemble of any GM V-8 engine ever built — once you know the tricks and tips, which you’ll get here.
Engine Blocks
The Gen III V-8 engine blocks are pretty much externally the same between the aluminum and iron versions. If you are looking to minimize the weight of your vehicle, there is no better way than using the aluminum LS1 or LS6 engine blocks as the foundation for your engine. These blocks are superior to any other small-block aluminum block on the market — period. An advantage to running the iron block would be that it can be bored to 4.000 inch (vs. the 3.893-inch LS1 engine bore) to achieve a 6.0-liter engine.
The 1997–’99 Gen III block (bottom) had these machined holes for a rear oil passage. This makes them less desirable than the 1999 and later blocks (top) with their open oil passage area.
If you’re trying to figure out what Gen III V-8 aluminum block to use, look for the ones with these cast-in-place slots in the base of the crank mains. These deal with high-RPM crankcase pressures better than previous block designs.
Look for the part numbers on the back of the blocks as a way to figure out what block you’re looking at. This is an early cast-iron 6.0-liter block.
If you are going to use the aluminum engine block for a big-hp engine, many builders suggest that you avoid the ’97-’98 LS1 engine block. These blocks have a shallow oil transfer galley at the rear of the block that limits equal flow of oil to the main lifter oil galleys. This galley is visible only with the rear cover removed. If the engine is complete, the valve covers on it will have their bolts around the perimeter of the cover (post- 1998 Gen III V-8 valve covers were a center-bolt design).
If the engine is torn down, the way to tell which block you are looking at is by removing the rear block cover. The ’97-’98 blocks have just two holes above the cam bore, while the ’99 and later blocks have a large cavity cast into the block above the cam bore.
Overall, the less-desirable early aluminum blocks look the same as the later blocks, but the casting number, located on top of the driver side of the bellhousing mount area on the ’97-’98 blocks, is 12550592, 12559846, 12559090.
The LS1 engine block will serve the majority of performance applications, but the LS6 aluminum engine blocks (casting number 12561168) that came in the Z06 are the most desirable blocks for hot-rod engines because they are designed to handle high-RPM, big-hp situations. For the most part, they are identical to ’01 and later LS1 blocks. Pre ’01 blocks have a hole machined through the main webs to improve bay-to-bay crankcase breathing. The hole cures the bay-to-bay oil-vapor pumping issues, but the cast-in ports found in the ’01 and later blocks are an improvement on that fix, so they are that much more desirable.
The 6.0-liter cast-iron engine blocks have incredible capability, as they are identical in design to the aluminum blocks, but the cast iron has more strength. Unfortunately, the added strength will cost you about 88 pounds. Notice the oiling found on early LS1s above and to the right of the camshaft bore. Also, note the 6.0-liter cast into the right rear bore of the block.
If you are building a big horsepower engine, the cast-iron version of the Gen III V-8 has been shown to easily handle over 800 hp. Most enthusiasts use the 6.0-liter block and the stock 3.622-inch crank, because this is an inexpensive combination good for making power.
The expensive choice for blocks would be to order a C5R aluminum block from GM Performance Parts. They are very expensive (over $6,000), but if you want to build a 4.125-inch bore, 7.0-liter engine, this is the only block available to do it with.
Tip: If you are going to use the high-performance C5R engine block as the foundation for your engine, make sure to grind out any leftover casting sand and sharp burrs. These racingintent engines usually have a fair amount of rough edges as shipped (the assumption is that a race shop will know to prep them in this fashion, but you may not).
Cranks
The same 3.622-inch crank is used in the LS1 and LS6 engine, so there is no reason to be swapping them. The crank is cast, but it has rolled fillets, which means the side edges of the bearing journals are compressed into a soft radius to minimize stress risers in that area. This crank has unusual strength for a cast piece and has a lightening hole drilled through it to improve bay-to-bay breathing and reduce rotating weight. If more cubic inches are desired or if you plan to make more than 550 hp, going to an aftermarket forged crank is a viable option.
The factory cast cranks are extremely capable and common throughout the car Gen III line (left). The truck cranks (right) have a different rear seal surface width.
The truck Gen IIIs use a variety of cranks, the main difference being the width of the rear main seal surface. The 4.8-liter crank has 3.270-inch stroke, while all the other Gen III truck engines use the standard 3.622-inch crank. If the Gen III V-8 engine is from a 2500 or Heavy-Duty truck, it will most likely have a wider seal pad on the crank. The car and truck seal surface diameters are common, but the heavy-duty trucks have a thicker seal surface. Making things more confusing with the truck vs. car Gen III V-8 crank issue is that in the last few years, many of the truck engines were redesigned to come with the standard, narrow “car” seal pad.
In general, the car crank is considered more desirable because it is lighter.
Tip: Be aware that the 2001 and later Gen III V-8s cranks run a tighter tolerance based on improvements in GM production capability.
Rods
You can use the stock connecting rods if you’re building an engine that will make 550 hp or less. If you do plan on using factory connecting rods, the way to go is with the LS1/LS6 rods for car engines.
The LS1 and LS6 use the same powdered-metal, cracked-cap rod, which uses a pressed-in piston pin. All of the Gen III V-8 factory rods are 6.096 inches in length and use 8-mm rod bolts.
The car and truck powdered-metal rods can handle over 500 hp with little more than the addition of aftermarket rod bolts.
There are a few versions of factory rod bolts that feature improvements that GM engineers have made over the years. Essentially, avoid the ’97-’98 rod bolts, but the bolts used from ’99 and beyond have been known to handle over 450 hp without issue. ARP and a few other fastener manufacturers make good replacement bolts for the stock rods and they’re good insurance — so it’s recommended that you install aftermarket rod bolts no matter what power you’re going to make.
Pistons
There is a difference in the material of the pistons used in the LS1 and LS6. Both are lightweight, flat top eutectic cast aluminum pieces with pressed on pins that can handle being in a 500+ hp Gen III engine. The original LS1 pistons are made by Mahle using an aluminum/silicon alloy called M124. LS6 pistons are made of M142, which has a higher content of copper and nickel than M124. M142 is stronger and exhibits reduced expansion at high temperatures than M124. This helped the Gen III team use tighter bore clearances to minimize oil consumption and piston noise while maximizing durability. Later pistons are also coated to minimize piston scuffing due to tighter tolerances.
Often, in a performance engine the stock pistons are replaced with aftermarket forged pistons, which is not a bad idea. The forgings are more forgiving to abuse, meaning they don’t fracture like the cast pistons under detonation, instead usually “lifting” a ring land, melting through the piston dome, or cracking off a small section of the ring land. A cast piston is more apt to simply self-destruct in similar situations.
In the truck Gen IIIs, the LQ9 piston is the best choice. These pistons are also eutectic cast aluminum, but they have a low-friction coating on the thrust faces of the pistons and floating piston pins. These pistons are not recommended in engines making more than 450 hp, as they are heavier than the LS1 pistons.
The hole in the factory aluminum piston in the number 4 hole on this LS6 engine is from the overuse of a 150-hp nitrous kit. Considering the temperature and detonation abuse it experienced, as shown by the speckled aluminum on the face of the piston, it’s impressive that the piston just burned instead of completely shattering.
Valves
The lightweight, hollow-stem valves are one of the cooler components in the 2002 and beyond LS6 engines. The hollow section of the exhaust valvestem is packed with a sodium-potassium mixture to help it remain cool, while the intake valvestem is left hollow. These valves are racing-inspired components that will improve throttle response, valve control, and heat management on any Gen III. More than that though, they have GM part numbers, which means they’ve made it through OEM durability testing and validation.
Tip: The ’02 and later LS6 valves are 0.6 mm longer than the previous LS1/LS6 valves to compensate for changes to the ’02 LS6 camshaft base circle. If you make the swap to these valves, use them with properly matched components — or for simplicity, just use the ’02 LS6 cam and valvesprings with them. The lifters, pushrods, rockers, retainers, and locks are all common.
The factory valvetrain works great up to about 6,500 rpm, but if you plan on revving the engine higher than that, plan on adding larger valvesprings and stronger aftermarket pushrods. The valve spacing was standardized early in the engine process for the smallest bore diameter of 96 mm, so all agree there is power to be found in increasing the intake-valve size and interlocking the valveseats.
Valvesprings
GM has literally spent millions developing valvesprings that can handle the valve motion of the Gen III V-8 with a minimum of drama. The Gen III valvesprings are one of the best compromises in pushrod engine technology. They are light and compact, yet perform similarly or better than a multi-coil performance valvespring. The “ovate” spring wire and “beehive” design are key to achieving this performance. Depending on your camshaft specs, the LS6 (PN 12565313) and ASA (American Speed Association) valvesprings will meet just about any street requirements.
The “beehive” LS6 ovate-wire valvesprings are impressive. Comp Cams and other aftermarket companies also make high-performance valvesprings of this design that will handle over 0.600 inches of lift.
As with all GM components, the development didn’t stop the day the Gen III showed up in 1997. To identify valvesprings, they are painted, tinted, and/or have a stripe painted on the length of the spring. Check out the chart above.
An added benefit is if you are using factory valves and valvesprings, the need to shim the valvesprings is greatly reduced. This is important as the valve uses the steel base washer to shed heat, and the more shims, the harder it is to shed the heat into the aluminum head.
This Tech Tip is From the Full Book, HOW TO BUILD HIGH-PERFORMANCE CHEVY LS1/LS6 V-8S. For a comprehensive guide on this entire subject you can visit this link:
LEARN MORE ABOUT THIS BOOK HERE
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Camshafts
By far, the best improvement you can make on your Gen III V-8 is to install a performance camshaft. For cost reasons, many of the early Gen IIIs had a common camshaft that didn’t optimize power, but was used because it simplified the assembly process and reduced cost. In 2001, GM began to proliferate camshafts for the various engines to show power increases.
Probably the most popular camshaft for any Gen III V-8 is the ’02 LS6 cam. It is truly an impressive piece and should be — GM engine development engineers utilize supercomputer modeling systems to get an engine combination close and then dyno test multiple cams at fractionally different parameters to isolate which is the best for a specific package. The LS6 cam is a result of that type of development and is a superior product that makes power in just about any Gen III engine combination that it is installed.
If you are looking for a little more aggressive camshaft, the ASA or “Hot” cams offered by GM Performance Parts take the lessons learned from the building of hot-rod engines and the ASA circle-track racing engine and offer them to you through GM Performance Parts.
One of the cool aspects of the Gen III V-8 is the cam can be changed without pulling the entire engine apart. Simply pull the valve covers, loosen the rockers, remove the pushrods, and pull the front drive. Spin the cam one revolution to seat the lifters in the lifter trays, and the cam can be slid out. Lube up the new cam with engine oil, slide it in, and reassemble the engine.
Tip: When swapping a camshaft, always check the valvetrain geometry by putting the lobe at 50 percent lift and visually inspecting whether the rocker tip is in the middle of the valvestem. Also, at max lift the rocker tip should not be off the tip of the valve. Use different length pushrods to correct valvetrain misalignment. This is especially important when swapping in cams with different base circles — like the ’02 and later LS6 cams.
The factory plastic lifter retainers will drain more oil if you drill 1/2-inch holes on their lower face. This helps to manage the oil better in the engine. The more desirable lifters are ’01 and later fully encapsulated versions (left). The early versions have some durability issues in high-hp applications.
There’s some real power to be had in the way of a cam swap, because GM used common camshafts to simplify the build process of their engines.
Tip: Whenever installing a more aggressive camshaft, it’s recommended that the stock pushrods be replaced with more robust aftermarket pushrods. The stock pushrods are optimized for light weight and have a tendency to flex and sometimes break in hot-rod applications.
Tip: On Gen III 6.0-liter LQ4-powered trucks, sliding in the ’02 LS6 cam while bolting on the small chamber LS6 heads will net about 400 hp. The higher compression of the engine is bled off by the longer duration of the LS6 cam at low-rpm but pumps up the highrpmhorsepower. You will need to run Premium fuel, though. The calibration will need to be altered to give the engine the appropriate fuel ratio, spark advance, and transmission line pressure adjustments to handle the newfound power.
As you can see from the cam chart on this page, as Gen III production continued, GM used more aggressive camshafts for increased power production. If you have an older Gen III engine, upgrading to a later cam is an easy way to find “hidden” power.
Cylinder Heads
The Gen III V-8 heads have small, internal changes throughout the portfolio that make substantial differences in their performance, but they’re essentially common. In general, the LS6 and LQ4/LQ9 cylinder heads are what everyone desires if they are building a performance engine (see page 28 for a rundown of all the details on the Gen III V-8 cylinder-head portfolio).
While all performance Gen III V-8 heads are cast aluminum with identical valve guide spacing (there were some iron Gen III V-8 heads made for the early truck engines that are not thought of as performance pieces), there are differences to justify the desires of performance enthusiasts.
The LS1 (left) and LS6 (right) heads look similar if you don’t know what you’re looking for — the next few pages will show you the details.
The LS1 chambers (right) are slightly larger than the LS6 chambers (left), but the shaping is more important to the engineers. They were able to get some better mixture motion in the LS6 chambers for additional power production.
The LS6 was developed for the Z06 Corvette, and the aluminum LQ4/LQ9 heads are a derivative of the LS6 heads — same ports, but 8-cc bigger chamber. If you are building a naturally aspirated (NA) engine, the LS6 heads are the best choice. If you’re building a boosted engine, the LQ4/LQ9 head is desirable because of the larger chamber.
As far as performance modifications, the valve spacing limits the valve sizes that can be packaged in the chambers. The biggest valve package that will fit without moving the guides seems to be 2.05/1.60-inch valves, though the valve seats will need to be interlocked, which we’re told increases power.
These heads are available with CNC machined intake and exhaust ports, which is really the way to go. GM spent a considerable amount of money to develop CNC ported LS6 heads because they thought CNC’d heads would be required to make 400+ horsepower. When they wern’t, these heads were applied to the Corvette racing program. These are available from GM Performance Parts. These heads do not have machining in the chamber area, due to the rules in the series they were created for, but they flow better than many fully CNC’d heads. Some aftermarket companies use the LM7 5.3- liter cylinder heads as a starting point, then CNC machine the intake and exhaust ports and combustion chamber. The reason they start with the 5.3 head is it is cast with a smaller combustion chamber (61 cc) than the LS6 and LQ9 heads, so they can machine the chambers without making them too big.
If you want to do some port cleanup work, here’s a tip. Don’t grind on the intake ports near the valve, but blend the ports to match up with the ports in the intake.
The “D”-shaped exhaust ports are a dead giveaway that you’re looking at an LS6 head. The pre-LS6 LS1 heads have oval-shaped exhaust ports. LS1 heads from 2001 and later were common to the LS6 (a positive to the GM method of commonality in the assembly plants). Notice the head on the left are sand cast and the one the right has the markings of being an SPM head — the more desireable piece.
Many of the road racers look for the LS6 heads with these triangles under the exhaust port between the headbolt bosses on the side of the cylinder heads. Many racers claim these are good for a 6-to-10-hp lift over the heads that otherwise look identical. The horsepower improvement are due to casting-core differences between sand casting (left) and semi-permament mold (SPM) casting (right), but we aren’t able to see any differences.
The LS1 and LS6 intake ports look similar, but the LS6 has slightly larger ports for improved flow. This photo is of one of GMPP’s CNC’d LS6 performance heads.
Tip: The Corvette road racers and other “in-the-know” Gen III performance enthusiasts are always looking for the Gen III heads that have what they call the “triangle” casting marks on the exhaust port side of the cylinder head as they have shown the ability to make more power than the heads that don’t have these marks on them.
These marks are left by the semi-permanent-mold (SPM) casting process used by two of the three cylinder head casting facilities creating heads for GM. Apparently, in random testing the sand cast heads have been about 5 to 7 hp down from the SPM heads. The SPM heads have shown practically no variation in power production.
Fasteners
The factory torque-to-yield cylinder head fasteners will handle over 500 hp, but you cannot reuse them. They are one-shot players only! These fasteners are very consistent and inexpensive, considering the job they do. But when GM says to only use them once, they aren’t kidding. One torque sequence, then throw them away.
As a purchasing tip, buy the cylinderhead fasteners for all ’97-’03 Gen IIIs in a kit (PN 12498545) that has enough fasteners to do both cylinder heads. The ’04 block uses all the same length head bolts that need to be purchased in a kit.
The single-use head bolts now come in a kit with a single part number, which makes sense because you can’t reuse these bolts once they are removed (i.e., you’ll need a full set every time you take off the heads).
Failing to blow out the blind bolt holes with compressed air to remove any liquid before you torque the bolts can lead to a worthless cracked block like this one.
Tip: This is important! Make sure you blow out all fastener holes with compressed air before installing fasteners. Many of the tapped holes in the Gen III block are “blind,” which means they are closed off at the bottom. Any oil or other incompressible fluid at the bottom of the hole could cause the engine block to crack when the fastener is torqued down. The engine block will be junk if fluid does cause a crack! So, avoid this big problem by blowing out all bolt holes.
Intake Manifold
Since the Gen III V-8 intake manifold is made of nylon and has a wall thickness of only 3 mm, there is little to be done with the internal shape of the ports. The LS6 intake that came out in ’01 is the piece to use, as it will flow enough air for 650 hp and beyond. The LS6-style intake became the standard intake on all LS1 engines in 2002, but it’s still called the LS6 intake.
The visual way to tell whether you are looking at an LS6 intake is to look for the flat, low-slung floor. The LS1 intake floor has more clearance between the bottom of the intake and valley plate cover on the engine. The LS1 intake floor also has a double swoop in it where it is deeper at the center.
Otherwise, the LS1 and LS6 intakes look almost exactly alike. There is a rumor this intake was raced in Corvette racing the season before it came out on the production Corvette and went undetected because it looked almost exactly like the LS1 intake. Hmmmmm.
The LS1 (left) and LS6 (right) intake manifolds look similar if you don’t know what to look for. The shape of the floor is what gives the LS6 intake away.
If the intake is mounted on an engine, the best way to determine whether you are looking at an LS6-style intake is by looking between the valley plate and the bottom of the intake. The intake with the “wing”-shaped floor on the top is an LS1 intake, the intake with the flat floor on the bottom is an LS6 intake. As a tip, all 2001 and later LS-engines came with the LS6- style intake.
If you don’t have any height restrictions and don’t have a problem with the visually challenged look of it, the truck intake is a cost effective way to make streetable power. We have been advised that it works in NA engines making over 400 hp below 5,500 rpm, or with a turbo making 700+ hp. The truck intake is a common part from the 4.8-liter to the 6.0-liter, so there are plenty of them out there.
Tip: Some road racers have been using the pre-LS6 steam tubes underneath the LS6 intake to improve cooling in cylinder number 7 (they previously had detonation problems in that hole). While the steam tubes weren’t used on factory LS6s, they will fit under the intake by slightly grinding down some of the stiffening ribs on the bottom side of the intake. Some racers just install the steam tube component and, during rebuilds, find some small indentations where the ribs come in contact with it.
Tip: The 2001 LS6 fuel injectors have higher flow, and to simplify the manufacturing process, the 2001 LS1s received these same injectors, also.
Another way to identify the LS6-type intake (right) is by looking underneath it. The LS6 intake has a flat floor, while the LS1 style intake has a lot of shape, with a single hump down the length of the intake. Also, the LS6-and-later intakes have the square ribbing between their intake ports, while the early intakes have large “x” ribbing.
By the time the LS6 came out, the GM Engineers improved the calibration of the engines and eliminated the AIR system inlet into the intake manifold. Because of this, hot-rodders can delete this system when upgrading to the LS6 intake. Use GM PN 12558346 to plug the hole in the intake.
This Tech Tip is From the Full Book, HOW TO BUILD HIGH-PERFORMANCE CHEVY LS1/LS6 V-8S. For a comprehensive guide on this entire subject you can visit this link:
LEARN MORE ABOUT THIS BOOK HERE
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Coils
There are three versions of coils used on the Gen III V-8 that are distinguishable by their external shape or their usage. There are two truck coils many hot-rodders describe by their external appearance — they are called the “round” and “triangle” coils. The LS1- engine coils are more rectangular in shape with the spark plug wire connector at the bottom of the coil. The triangle truck coil looks similar to the LS1 coils but the spark plug wire connector is in the midsection of the coil. We’re told by GM engineers that the differences are merely external, as a result of the three different coil suppliers.
The factory coils have about a 60 mJ spark, which can knock you on your can if you get the full blast — so these coils are good for big power. In fact, the stock coils have been known to handle over 1000-hp turbo applications with no problem. They’ve gotten a bum rap from the blower and turbo crowd as many claim the coils struggle to handle highRPM, big-number power. Actually, the problem is not the coils, but with the spark dwell timing.
The three styles of coils that come on Gen III V8s from the factory are shown here. The LS1/LS6 coil is on the right, and the two styles of truck coils are shown in the middle and on the left. Many engine builders believe the round truck coils perform better in high-horsepower applications than the other two coils.
On boosted engines, the dwell needs to be lengthened at higher RPM but kept near stock levels at low RPM to avoid overheating the coils. Changing the dwell in the production calibration is not easily done, but there are some uplevel and newer aftermarket controllers, like the Big Stuff III system, that will allow spark dwell changes vs. RPM. It can be tough to follow GMs PN scheme, so finding coils using the visual method works best in this case.
Oil Pans
Depending on what vehicle you are installing the Gen III V-8 in, GM has an oil pan for you. If you are installing into a vehicle that came with a Gen III engine, there really isn’t any need to swap to a different pan. For instance, the Z06 LS6 engine runs the same oil pan and oil scraper as the Corvette LS1. The same can be said for the LQ9; it uses the same oil pan as the lower-hp LQ4 and smaller 4.8- and 5.3-liter engines.
The Corvette batwing oil pan (left) looks much different than the Camaro/Firebird F-body oil pan (middle) and full size truck/SUV oil pan (right). The F-body pan gets the most hot-rod usage by far because of its shallow front section, 5.25-inch deep rear-sump design (flange to bottom), and availability.
These two Corvette oil pans are identical except the one on the right is a two-piece design, while the pan on the left is the early one-piece pan. Use the two-piece pan as it’s easier to clean and check oil pick-up height.
The Corvette pan is an extremely shallow rear-sump design often described as the “batwing” pan. As with all Gen III oil pans, it’s cast aluminum and comes with a factory installed oil scraper tray attached to the main bearing cap bolts. But the ’Vette pans were originally made as a one-piece design, and then refined into a two-piece design. The two-piece pan is more desirable, because it’s easier to clean, check the pickup height, and install.
All of the GM oil pans come with crank windage trays and oil containment trays to minimize oil wrapping around the crank and sloshing in the crankcase. Notice the F-body pan is shortened as it won’t fit in the shallow front section of the pan, but the ‘Vette and truck windage trays are full length.
The Camaro and Firebird (F-body) oil pans are a rear-sump design also, but they don’t have the kick outs of the batwing Corvette pan. The F-car pans also have a shortened oil scraper because the front of the pan gets too shallow to fit the scraper all the way to the front, as it does on the ’Vette and truck oil pans.
The truck oil pans are rear sumps, but the sump is three inches deeper than the sumps on the car oil pans. This is good for powerful engines, as it is more oil to lubricate and cool, and also provides room to get the oil away from the spinning crank. These pans are sometimes used in hot-rod applications where hood height is not an issue, but usually the F-car pan is selected.
The pans are a structural member of the powertrain, so the transmission mounts to the oil pan and the engine block — delivering forces to both. This was done for improved NVH. We’re told you can use an aftermarket oil pan that doesn’t have these holes if you really want to. But for those that want to save some money and want a quieter, smoother-riding vehicle, it’s good to know the factory oil pan has an enormous amount of development in it.
If you are using the Gen III in a custom application, you might have to trim the sump or crossmember to create clearance. There are some aftermarket pans now coming onto the market, but in general, most hot-rodders are cutting off portions of the stock pans and welding on plate aluminum to fit various applications.
Throttle Body
The factory throttle bodies come either as a cable actuated or as an electronic throttle control (ETC) unit. Both come in multiple inside diameters. For performance applications, usually bigger is better, and smoothing the inside surfaces will show a small increase in performance. Going too big with a cable actuated throttle body can make lowRPM driveability challenging, which is part of the reason GM went with the ETC — it allows minute application adjustments based on wheel speed, engine speed, and other vehicle sensor inputs to make 405-hp vehicles easy to drive.
The most desirable throttle bodies are the 85-mm inside diameter units that came on the Corvettes and trucks. Some of the truck units were cable actuated, so they are sought out for F-cars and hot rods. The ’Vette has had the 85-mm ETC since it first came with the Gen III in 1997. Various trucks (mostly all-wheel-drive trucks) have come with the 85-mm ETC.
The early 75-mm LS1 throttle body (left) can be easily replaced with an 80-mm LQ4 throttle body (right) for an increase in airflow. The LS6 throttle bodies are 80 mm, but they are electronic throttle control (ETC), whereas the LQ4 throttle body is cable actuated.
GM is slowly going to all ETC, like the LQ9 (left) and LS6 (right) shown, so hopefully it won’t be long before an aftermarket company comes up with an ETC throttle pedal for hot rods. This way, automotive enthusiasts won’t have to keep retrofitting back to cable throttle bodies (like the LQ4 unit shown in the middle)
Tip: For improved throttle-body airflow, smooth the transition surfaces up to and after the throttle blade with a 180-grit tootsie roll on a grinder. Be careful not to touch the area where the throttle blade seats in the body, as this will negatively affect idle quality.
Mass Airflow (MAF) Sensors
The simple modification that should be performed to every MAF sensor is the gentle removal of the inside screen. GM obviously saw the light on this after a few years, because the ’02 Z06 Corvette doesn’t have a screen in the MAF.
Changing to a larger or higher-flowing MAF sensor will often change how the computer interprets the amount of air entering the engine; so check this before installing a new MAF.
Tip: To remove the screen, carefully negotiate two fingers through the back of the MAF (past the wires that read the airflow) until they are touching the screen. Push on the screen until it pops out. Some truck MAFs come with a lock ring that needs to be removed before the screen can be pushed out. You are done with this performance improvement.
Tip: The screen is used to straighten the air coming into it to minimize false airflow readings, but on the LS vehicles with straight intakes, the screen isn’t required. On trucks where the air tube approaches the MAF from the side, the screen should be left in unless you’re willing to make calibration changes to account for the new readings.
To remove the screen, carefully push from behind to unseat it from the MAF body. Be very careful not to touch the sensor components, as they are very fragile and easily damaged.
Airbox
While there are many aftermarket airboxes available, GM has continued to search for power in the factory airboxes over the years. Just swapping a Z06/LS6 intake box and air tube in the place of an LS1 engine airbox won’t cause a huge increase in power by itself. But it does allow more air to pass into the engine, which becomes increasingly necessary as other performance parts produce more power with the same engine.
The MAF on the left is from an LS6 engine, while the MAF on the right is from a 5.3-liter truck engine. The LS6 MAF screen is easily popped out, but the truck MAF has a lock ring that must be removed before the screen can be popped out.
Some of the possible airbox upgrade ideas are listed below:
Corvette: Z06 LS6 5.7-liter Airbox on LS1
Camaro: SS airbox and hood from SLP on LS1 Camaro
Firebird: Ram Air airbox and hood from SLP Firebird
Trucks: Escalade LQ9 6.0-liter airbox in V-8 truck
Tip: A simple way to increase the breathing capability of the stock airbox is to cut holes in the bottom of the airbox. GM doesn’t put these holes in because the vehicles have a tough time passing the water ingestion testing (simulating situations like the Alabama porch washer and flooded road crossing) and allow more intake noise to be heard. Since you aren’t going to be fording a river anytime soon (are you?) and the intake noise soothes your hot rod soul, opening up the stock airbox with some holes is all good.
The SS and Ram Air hoods are very effective at getting cold air into the F-body intakes. They mate up with the stock airbox and are impressive in their packaging. They are still available new from GM dealers and SLP.
Written by Will Handzel and Posted with Permission of CarTechBooks
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