When you’re thinking of building a performance Chevelle, one fact is undeniable: you need more power than the stock Chevelle came with. Even the engine that set the muscle car world on its ear—the venerable and almost myth-like LS6—is outdated for what most people want in their modern Chevelle.
An engine swap doesn’t necessarily mean changing to something totally different under your hood. If you have a small-block car, you can now build a 427-ci version of the old mouse motor that makes more than 600 hp and runs on pump gas without any power adders. Factor in a supercharger or turbo, and things can get really crazy. And if you have a big-block, the sky is the limit.
This Tech Tip is From the Full Book “CHEVELLE PERFORMANCE PROJECTS: 1964-1972“. For a comprehensive guide on this entire subject you can visit this link:
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Even swapping out a small-block for a big-block isn’t terribly challenging, since these cars were available with both originally. People have been swapping back and forth since 1964, so there is a plethora of parts and knowledge on exchanging a mouse for a rat and vice versa. You can have either small-block or big-block in all-aluminum, short-deck, tall-deck, strokers, and just about anything else you can dream up. I don’t want to oversimplify these swaps, but frankly, there’s a ton of really good information already available on how to do this.
Gen I vs LS
The engine swap detailed in this chapter is the most commonly talked-about and the least understood by the majority of Chevelle owners today. I’m talking about replacing your Gen I small-block or big-block with an LS engine. If you look at the top-per-forming Chevelles at national events, it’s hard to find one without some version of an LS engine between the vintage fenders. And by the looks of automotive magazines, you’d swear there isn’t a Gen I engine used in these cars anymore. I’d like to be the first to tell you that isn’t true.
And here’s another myth I’m happy to set straight: An LS swap is neither easy nor inexpensive. To help with perspective before you decide you need an LS, consider that a Toy-ota Tundra V-8 has as much in com-mon with your Gen I small-block as an LS engine. Blasphemy, you say? Let me explain.
The Simplicity Factor
It’s a common misconception that all Chevy engines are easy to swap and have a ton of commonal-ity among variants. That’s probably because since 1955, with the introduc-tion of the first small-block Chevrolet V-8 engine, all small-block Chevy engines retained the critical specs. Those include the head-bolt spacing, the accessory bolt-hole locations on the block, the bellhousing bolt pat-tern, and so on. The commonality became ingrained in performance builders to the point where most took it for granted. It nearly caused pande-monium when the one-piece crank seal was introduced, changing the crank, seal, and flywheel/flexplate centering register. These are now all referred to as Gen I small-blocks.
Factor The introduction of the LS design in 1997 ushered in a new era of Chevrolet engines. It shares nearly nothing with the Gen I. The exhaust ports are in a different loca-tion and the bolt pattern is different, absolutely none of the old accessory brackets bolt on, the water pump is completely different, the bellhous-ing bolt pattern is different, and the external dimensions are different. To add to the challenge, all LS engines offered in production vehi-cles were fuel-injected, which means no factory carbureted intake mani-folds and no mechanical ignition distribution system—it’s all com-putercontrolled.
So, why the emphatic acceptance of an engine that requires the learn-ing curve of a performance BMW or Mercedes engine? It is due in part to the fact that it is a Chevrolet V-8, and also because it is still a push-rod engine. One of the biggest arguments for the LS engine design, though, is that the valve location and port design in the cylinder heads is fan-tastic for making power. This wasn’t possible in the Gen I design, even in highly modified cylinder heads requiring unique intake manifolds and relocated exhaust ports. The LS arrangement solved a great many problems in moving the air/fuel mixture from the intake manifold into the cylinders with great effi-ciency. This cylinder head design also smoothes out more radical camshaft profiles which can be used without the choppy idle and decreased low-end torque that you would expect.
Another reason the engine is popular is that it has been mass-produced for more than a decade, placing literally millions of them on the road. They are also, to this day, the most powerful mass-produced engines General Motors has ever produced.
The bottom line is that the LS engine family is growing in popularity for engine swaps, and is definitely favored among the top car builders. This has led to a growing availability of parts to make installing one in your Chevelle a little easier than dropping in the aforementioned Toyota Tundra V-8. But this swap is far from a drop-in, bolt-on exercise. In addition to some custom work, you have a lot of choices to make. That starts with which LS engine to use.
Over the years, the engine has been available in all-iron, all-aluminum, and iron-block-with-aluminum-cylinder-heads versions. The displacement has varied from Vortec 4.8-liters (295 ci) to LS7 7.3 liters (427 ci), and power has ranged from 270 hp to 638. And the engines have been used in everything from pickup trucks to Corvettes.
Choosing your engine comes down to what is most important to you and how you use your car. And, naturally, your budget is a factor. An all-aluminum version has an advantage for all types of racing, reducing the front weight of your Chevelle more than 100 pounds. These engines are typically more expensive, but are also usually higher performance in stock form.
Another factor to consider is whether you’d be happy with the stock power. If not, you likely need to replace the crank, rods, and pistons to create a durable engine. It’s quite easy to spec out a $10,000 LS engine to make 500 hp or more.
Which brings us to brand-new LS engines from the Chevrolet Performance bin of crate engines. When we went to press with this book, Chevrolet Performance offered nearly a dozen versions of the LS engine as complete crate engines, plus a few race versions. They range from an economical LS327 (which is an iron-block 5.3-liter (327 ci) minus intake, exhaust, and accessories) all the way up to the LS9 supercharged 6.2-liter (376 ci) found in the 2012 ZR1 making 638 hp.
If you’re looking for a drop-in LS engine that’s brand new, this is a great way to go. No rebuilding, no used engine parts. But you still have quite a bit of homework to do before it’s bolted into your car and purring like a kitten.
On the used-engine front, you often hear about someone finding a complete LS engine for just a few hundred dollars. That might be tempting, but realize that these are usually 100,000-plus-mile engines that require rebuilding, and the displacement is seldom more than 5.7 liters (350 ci). One of the most sought after salvage yard engines is an L92/L99 6.0-liter engine out of a Denali or Escalade. These are all-aluminum. You can toss a carb and headers on one and make 430 hp and still have a 650-rpm idle without changing any internal engine parts.
The LS7 may be one of the most desirable candidates for swapping. It’s the largest in displacement and the highest in naturally aspirated power output from the factory. It’s all-aluminum, and it’s pretty cool to have a 427-ci engine in your classic Chevelle. There’s usually a “however,” and the however in this case is that it came from General Motors with a dry-sump oil system, and the oil pan requires significant surgery to your Chevelle crossmember for proper fitment. The unique crank makes it difficult to change to a wet-sump oiling system. I’ve seen a couple Chevelles with the LS7, but there was a lot of custom fabrication involved.
The biggest number to keep in mind is how much the various engine-swap components cost. It’s not uncommon to spend $4,000 on parts just to put an LS into your Chevelle.
While this may be one of the most-talked-about swaps today, before committing to an LS engine, ask yourself why you want one and determine how much it really costs. Replacing a 400-hp Gen I small-block with a 400-hp LS is an expensive venture for the benefit of being able to tell people your Chevelle has an LS engine in it. On the other hand, if you have no engine in your Chevelle, or are already planning on upgrading the headers, accessories, transmission, and so on, the LS should definitely be on your consideration list.
Project 1: LS Engine Installation
Step-1: Prepare for Installation
There’s quite a bit of prep to do before you’re ready to hoist your LS engine over your fenders for the first time. The very first thing you should do is buy yourself a good set of metric tools. That’s right, metric. Everything on these engines is metric. Start with a good kit, like this one from Kobalt, which comes with sockets, wrenches, and Allen wrenches. You also should have a set of six-point sockets, ratcheting wrenches, and Allen socket drivers.
Step-2: Choose Adapter Plates
LS engines use a totally different style of engine mount compared to older Chevys. Several companies offer adapter plates that bolt to the sides of the block and accept a traditional engine mount for a simple solution. However, all of these adapters place the engine in a slightly different location, fore and aft, in the chassis. The headers and oil pan may come in contact with the body or subframe. My recommendation is to get the engine mount adapters, headers, and oil pan from the same company, which means you have to consider all of the components when selecting one. The billet aluminum adapters shown are from Hooker, which also makes full-length 1¾-inch primary tube headers and oil pans. Three versions of the adapters are available: one positions the bellhousing flange at the stock location, another moves it forward, and a third moves it backward. Keeping the engine at stock location or moving it rearward is best for fitment of the headers and oil pan, as well as weight balance.
Step-3: Install Adapter Plates
This Trans Dapt engine mount adapter is installed on an LS3 engine. It requires a bit of grinding to clear a boss on the engine. Use Moroso solid engine mounts that are 1/4 inch taller than factory to help with oil pan clearance in an early Chevelle. The engine in the 1964–1967 Chevelles sits more than 1 inch closer to the engine crossmember and steering linkage than the engine in the 1968–1972 cars. This creates a challenge with oil pan clearance, and moving the engine up slightly with these engine mounts helps. Moroso also offers stock-height solid mounts. I prefer solid engine mounts because nothing moves as the engine revs. They do transfer more vibration to the chassis and, ultimately, the driver and passengers. Polyurethane mounts from Energy Suspension are an option for better control and durability than rubber, and better vibration isolation than solid mounts.
Step-4: Select Headers
The exhaust manifolds on some high-performance stock LS engines provide decent flow. But most of them do not fit in the chassis of a Chevelle very well. The best solution is a set of headers made specifically for an LS engine that’s going into a Chevelle. Hedman Headers makes mid-length and full-length headers designed to fit with Trans Dapt engine adapter plates. They have 13⁄4-inch primary tubes and 3-inch collectors. Hooker makes full-length headers designed to work with its engine adapter plates. You can also have custom headers made. This is usually more expensive and requires access to a talented fabricator, but it normally results in the best-fitting headers.
Step-5: Fit Headers
I used Hooker black ceramic-coated 1¾-inch primary tube headers with 3-inch collectors for installing a Chevrolet Performance 515-hp LS3 into a 1966 Chevelle. The headers were the best-fitting set I’ve installed on a Chevelle out of the box. However, I did have to massage them with a hammer in a couple of places because of our specific situation. First, the number five tube hit our steering shaft. I had previously converted the car’s steering shaft and were running a Borgeson 1-inch double-D shaft. This may or may not be an issue with the stock steering shaft on 1964–1967 cars, but I suspect it will be really close if not touching. It should not be a problem on the 1968–1972 Chevelles. To create a smooth dimple for clearance, wrap an impact socket with several layers of masking tape, place it on the tube at the correct area, and hit it with a hammer. Lay the port flange of the header flat on the ground to keep from bending it.
Step-6: Weld Temperature Sensor Bung onto Header
Most of the headers available for LS swaps come with oxygen sensor bungs welded into the collectors. If you’re using shorty headers, weld these bungs into the exhaust tubing approximately where the exhaust meets the flat section of the floorboards. If you’re using an aftermarket fuel-injection system or controller for the factory hardware, it most likely comes with weld-in bungs. If not, you can purchase them from most aftermarket fuel-injection companies.
Step-7: Oil Pan Options
The oil pan for an LS engine is one area that highlights the difference between 1964–1967 Chevelles and the later 1968–1972 cars. Because the crossmember, inner tie rods, and center link are closer to the oil pan on the early cars, finding an oil pan that fits is extra challenging, and most oil pans designed for Chevelles fit the later cars better than the early ones. Many of the most desirable LS engines come in Corvettes, trucks, or other applications that use an oil pan that don’t fit in any Chevelle. The sump generally comes too far forward, and the front section hangs down too low for crossmember and steering linkage clearance. Some people opt to cut, plate, and box the crossmember and convert to rack-and-pinion steering. If you go this route, make sure the manufacturer of the rack-and-pinion system assures you that its system fits your plan. Every oil pan comes with an oil pump pickup tube specific to the pan.
Step-8: Inspect Oil Pan Options
Here are some oil pan options. On the left is a Holley LS conversion pan for Chevelles. The sump is generous and sits about the same height as the crossmember in the car. The pan in the middle is an F-car pan, used on LS1-equipped Camaros and Firebirds in the 1990s. If your LS engine is moved as far back as possible in the chassis, this fits, but barely. It also makes getting the engine in and out extremely difficult because of the tight fit of the oil pan on the crossmember and the engine against the firewall. Street & Performance sells a modified version of this pan that reduces the sump, making it a better fit in the chassis. The pan on the right is a muscle car swap pan from Chevrolet Performance. The shape of the pan solves some issues, but the extra-deep sump hangs more than 1 inch below the crossmember in an early Chevelle. It also contacts the crossmember and steering linkage on the early cars. Milodon makes sheet-metal oil pans for LS swaps. A lot of people use these without any trouble, but the factory cast-aluminum pan is a structural part of the engine, providing strength on the bottom end. Reports vary as to how well these fit the early cars, although they do seem to fit the 1968–1972 cars well.
Step-9: Modify Pan for Clearance
The Holley oil pan requires fewer modifications to fit an early car than the others. Also, Holley is currently developing a new pan that should address these issues, as well as provide baffling in the sump for road and autocross racing. Use the Moroso 1/4-inch-tall solid engine mounts and insert 0.150-inch shims between the engine mounts and adapter plates to raise the engine another 1/3 inch in the chassis. This is sufficient to create a tiny gap between the Holley oil pan and the crossmember. With solid engine mounts, you don’t have settling or movement, so a tiny gap is enough. The fix for inner tie rod clearance is much more involved. With the engine in the car, mark the sides of the pan with the amount of room needed. Then raise the engine just high enough to be able to fully steer lock to lock, and trace the arc of the linkage on the bottom of the pan. The tie rods deflect when the car is cornering hard, so you need to add about 3/16 inch to all of the measurements. The result is that two windows need to be cut into the cast-aluminum oil pan by using an air-powered cut-off wheel and a reciprocating saw.
Step-10: Fit Pickup Tube to Oil Pan
If the oil pan you plan to use comes with a pickup tube running along the opposite side of the engine than the one you’re removing, or it connects to a different mounting location, you need to modify the windage tray. For example, the LS3 came in a Corvette and had the pickup tube on the driver’s side of the engine. The Holley pan (and most LS oil pans) has the pickup tube on the passenger’s side. You need to mock-up the placement of the tube under the engine and mark where it interferes with the windage tray. Typically, you need to cut away material near the mounting stud, and you may also need to trim the mount on the new oil pickup tube. Do so carefully, however. You do not want the pickup tube mount to break, allowing the tube to fall, potentially suctioning itself against the bottom of the pan and starving the engine of oil.
In early Chevelles, you need to reduce the depth of the oil pan where the pickup tube runs. This means cutting and welding the tube so it is as tight against the bottom of the engine as possible. This modification requires extreme care, because even a pinhole in the welds allows the oil pump to suck air, aerating the oil being pushed into the engine. That’s bad. You can order an F-car pickup tube from General Motors, which starts out fairly tight against the engine, and start cutting. You need it to be even higher than the original F-car tube, so make the first cut at the first bend in the tube as it connects to the pump. Then cut and weld a section to get the clearance you want and position the pickup exactly where Holley designed it in the oil pump. Hand-file the cut pieces and TIG-weld them for clean and controlled welds. Then pressure-test the tube by plugging the ends, applying air pressure through one of the plugs, and running soapy water over the tube to check for air leaks.
Step-11: Install Oil Trap Door in Pan
You can build a trap-door system in the sump area of the Holley oil pan for better oil control during hard cornering. The idea is to create a box around the oil pump pickup. By using trap doors to make it easy for oil to enter the area, but hard to exit during cornering, this reduces the chance of momentary oil starvation during high lateral G maneuvers. The Holley pan comes with the baffle shown, which bolts to the pan to further reduce windage. ABC Performance custom fabricated the metal insert located in the sump area of the pan. This cuts the horizontal surface area of the sump section by about 40 percent. Rivet this piece to the original bolt-in baffle. Both pieces need to be trimmed to fit the oil pump pickup tube, which means mocking up all of it on the engine, trimming, and repeating as needed.
Step-12: Install Oil Trap Door in Pan (Continued)
Most hinges are designed to screw onto a building’s door and have holes cut in them. It may take a bit of searching local hardware stores to find some without holes. You also want steel so you can weld them in place. Before they are welded in, cut them to fit around the clearance openings for the pickup tube. After cutting them, make sure that they still swing freely. Used a TIG or MIG to weld them in place.
Once the hinges are welded in, drill 3/4-inch holes where they are covered with the hinges down. These don’t have to seal. The idea is just to slow the oil and keep it close to the pickup tube. The hinges don’t fully open when installed, because they will contact the pickup tube. But they open enough to let oil enter the area when turning one direction and close to restrict oil movement in the other direction.
Attach the trap-door system to the baffle. Set the system in place and bolt the baffle to the pan. Measure the location of the oil pump pickup when installed, and position the trap-door system accordingly. Mark the position of the system on the baffle and then remove everything. Clamp the system to the baffle and drill several 1/8-inch holes through both pieces. Use rivets to attach them. Next thoroughly clean the entire assembly. For the final installation, use Blue Loctite on the four bolts that hold the baffle to the oil pan.
Step-13: Inspect Finished Oil Pan
This is the finished, modified Holley pan prepped to fit an early Chevelle chassis. I had ABC Performance bend and TIG-weld aluminum sections into the windows I cut out for inner tie rod clearance. This is tricky welding, as you are joining sheet aluminum to a cast aluminum pan. And oil has a way of seeping through the tiniest pores. The oil pan is a significant challenge for owners of early Chevelles wishing to do an LS swap.
Project 2: Water Pump and Front Accessories Installation
Step-1: Select Front Accessories Drive System
Most desirable LS engines do not come with a front accessory drive system that fits in a Chevelle, or at least they don’t look very nice. Most of the Chevrolet Performance crate engines come with a water pump and damper, but nothing else. In either case, you need an accessory drive system designed to mount the accessories you want and fit it into the Chevelle chassis. There are several companies offering kits, including Billet Specialties, DSE, and March Performance, Inc. They typically come with the accessories (power steering pump, air conditioning compressor, and alternator) because the variance in what could be used might lead to fitment issues with the brackets. Including the accessories with the kits ensures that they fit in the brackets and don’t cause interference problems.
General Motors used quite a few different water pumps, depending on what vehicle the LS was installed in and what accessories it had. Because the water pump has most of the accessory mount bolt holes in it, most aftermarket companies provide a new water pump with their kit. Some also provide a new damper for similar reasons. I installed a Billet Specialties Tru Trac accessory drive system with power steering and alternator (no air conditioning) on this car. If your engine has any accessories on it, remove these, as well as the water pump.
Step-2: Install Water Pump
The Billet Specialties accessory drive system comes with an Edelbrock aluminum water pump. Pay attention to where the various fasteners, studs, and spacers are supposed to install. Also, use anti-seize on any fasteners installed into aluminum. Bolt the water pump to the block. The Edelbrock water pump moved the upper radiator supply hose from the driver’s side to the passenger’s side of the engine. This is the more common placement on an LS engine, placing the inlet and outlet on the same side of the engine. (This one is on the driver’s side because it was a Corvette engine.)
Step-3: Install Accessory Brackets
With the new water pump in place, you can start bolting on the accessory brackets. Most accessory drive kits come in polished aluminum finish. This kit’s parts are powder-coated black. Most of the brackets are dual-purpose. This one mounts the alternator and is the top bracket for the power steering pump. The pump provided with the Billet Specialties Tru Trac is a remote reservoir style, but does not include a reservoir. You can use an original-style remote reservoir found on most late-model vehicles or order an optional billet aluminum reservoir from Billet Specialties. In either case, you need to remotely mount the reservoir, such as to the radiator core support right next to the radiator.
Step-4: Install Harmonic Damper
The Billet Specialties system includes an ATI damper because different dampers of various thicknesses were used by the factory, and this new damper eliminates that variance. However, there is no woodruff key in the crankshaft to align the damper. Using a flashlight, you can see the slot farther back for the key that drives the oil pump. ATI sells a kit that lets you pin the damper to the crank to keep it from spinning on the snout of the crank. This is advisable for all LS engines and should be considered required on any engine making more than 500 hp, or that you intend to rev above 6,000 rpm. The kit consists of a locating device (shown here bolted over the end of the crank), two drill bits, drill guides, and a pin.
Once the crank is drilled and you’ve cleaned all of the metal shavings away, install the new ATI damper. The damper has a very tight tolerance to the crankshaft’s outside diameter. If you align it perfectly, and there is absolutely no damage to the outside crank surface, the damper slips right on. Otherwise, you need to use an installation tool to pull the damper onto the crank. The Billet Specialties system comes with a brand-new GM damper bolt. Before you use the new bolt, install the old one and torque it to 240 ft-lbs, and then remove it. This seats the damper completely without stretching the new bolt. Then install your new bolt and tighten it to 37 ft-lbs. Finally, turn the bolt an additional 280 degrees (mark a reference point on the engine so you know when you reach this). It is most likely necessary to work in two increments of 140 degrees instead of trying to tighten the bolt with one almost full rotation of the ratchet.
Step-5: Inspect Accessories
This is what the setup looks like when complete. The pulley came already installed on the new PowerMaster alternator from Billet Specialties. You can choose either a 105-amp alternator or one that makes 140 amps. The pulley on the lower passenger’s side is an idler pulley. This is spring-loaded and applies tension on the serpentine belt. In the Billet Specialties system, this is a unique part. Some other kits use a GM idler pulley, so you can get a replacement just about anywhere. The pulley that’s high on the passenger’s side is where the air-conditioning compressor goes. If you do not have air conditioning, it’s just a dummy pulley to make the serpentine belt route properly.
Project 3: Engine Installation
Step-1: Install Engine in Chassis
It pays to do your homework in advance and prep the engine as much as possible before lifting it over the sheet metal. You will probably still have to put it in and take it out a couple of times, but this is better than a dozen times. With the radiator out of the car, there is plenty of room to drop the engine into the engine bay with the front accessory drive and complete clutch assembly bolted on. It gets tight if you also have the bellhousing bolted in place. However, if you are using engine mount adapter plates that place the engine farther back in the chassis against the firewall, the upper driver-side bellhousing bolt is extremely hard to get to once the engine is in place, so installing the bellhousing first is a good idea. Some people like to bolt the engine and transmission together and use a tilting engine lift to swing it all in at once. If you don’t want to risk damage to the painted firewall or core support, install the bellhousing and transmission later. It is a very good idea, however, to bolt the transmission to the engine on the ground before installing the engine to trial-fit everything. If you don’t do this you may end up lifting the heavy transmission into place several times under the car to get things sorted out.
Step-2: Select Wiring Harness for Engine
Once the engine is bolted to the frame for the last time, you can start wiring it. If you have retained the factory fuel-injection system, you have a few choices for an engine controller and wiring. You can modify the factory wiring if you grabbed it with the donor engine. There are forums that describe how to do this, but I don’t think it’s the best option. There are lots of sensors and variables used in a factory setting that aren’t needed and may not exist in a retrofit, creating the potential for a frustrating experience chasing engine codes. Going this route also eliminates the opportunity to tune the engine for performance rather than for emissions; the factory system must balance both, often at the detriment of performance. There are several aftermarket ECUs designed for retrofits. These come with a wiring harness that plugs into the factory engine sensors and connects to the original fuel injectors. Most control the ignition spark as well. Shown here is a Holley HP system, which allows you to use a laptop to modify the fuel and spark maps to fine-tune the engine. You can also purchase an optional handheld controller, which allows you to make broad changes to the fuel and spark without a laptop. This kit literally takes just a few hours to install (mounting the ECU and routing the wires are the hardest parts if your exhaust already has a bung for the oxygen sensor).
Step-3: Install Drive-by-Wire Throttle System
If you use the factory fuel injection, there is another obstacle. Almost all of these engines, and certainly the desirable versions, came with a drive-by-wire throttle. That means there is no throttle cable, and no provision to add one. You can purchase a drive-by-wire throttle pedal from Chevrolet Performance or Lokar. The advantage of this is that you do not need a cable or linkage protruding through the firewall. Some owners do not want to rely on a fully electronic drive-by-wire throttle, and therefore opt for mechanical throttle linkage. If you use a FAST EFI crate/ transplant kit, a new cable-operated throttle body is included.
Step-4: Install Starter
If you have a higher-horsepower factory LS engine or a built-up one, you want a starter with more cranking power than that of a factory unit. MSD makes this starter as part of its Advanced Power System (APS) line. Its core features are a 3-hp electric motor and 4.4:1 gear set. Internally, it has a very high quality assembly, including a balanced armature, and it is guided by two ball bearings for smooth engagement. A key advantage is that the billet mount can be clocked in different positions to fit in tight applications, which you have with headers in a Chevelle chassis. To fit the MSD starter, flatten the inside of two header tubes approximately 3/16 inch using the technique shown earlier. The starter comes with shims, which may be necessary for perfect alignment on the flexplate or flywheel, but this application didn’t require any. In most cases, you need to install the starter and passenger-side header at the same time.
Step-5: Select Radiator
Technically, you don’t need a new radiator. However, for a clean installation devoid of funky adapters and ugly hose routing, a new radiator, such as this Flex-a-Fit aluminum radiator from Flex-a-lite, is in order. Plus, you are probably stepping up in power, which means you should increase the cooling capacity as well. The inlet and outlet should both be on the passenger’s side of the radiator for an LS swap. This makes the radiator a dual-pass (the coolant enters on the passenger’s side, flows to the driver’s side, down to the lower half of the radiator, and back to the passenger’s side before returning to the engine) providing more cooling. The inlet and outlet should both be 1½ inches in diameter.
Step-6: Fit Steam Tube or Install Block-off Plates
Coolant does not flow through the intake manifold on an LS engine. This means that coolant in the engine is higher than the water outlet connected to the radiator. LS engines have a steam crossover tube at the front of the block connecting the coolant passages in the cylinder heads. This allows air trapped in the system to escape and be routed back into the cooling system. There are several ways you can deal with this steam tube. You can drill and tap the flat surface of the water pump and connect the steam tube to it. You can also have a fitting installed in the radiator and route the steam tube to the radiator with the upper radiator hose. If you choose to remove the steam tube and install GM block-off plates. If you block the passages, you need to remove the plugs when you first fill the radiator with coolant or water and allow all of the air to escape the system. When only water or coolant flows out of these holes, insert and tighten the plugs.
Step-7: Install Recommended Thermostat
If you’re using a salvage-yard engine or a crate engine from Chevrolet Performance, it has a thermostat with a higher opening temperature than you probably want. The “88C” stamped in this thermostat tells you that it is rated to open at 88 degrees C (190 degrees F). That’s not too bad, but some are even higher. If you run fuel injection, I suggest that you ask the controller manufacturer what temperature thermostat it recommends. The manufacturer’s fuel and timing maps are affected by the operating temperature of the vehicle. Typically, a thermostat between 160 and 180 degrees F works well with aftermarket controllers and helps keep the temperature of the engine lower, especially at highway speeds. Higher-temperature thermostats are used from the factory to help the engines meet emissions standards, but are not necessary for the engine to run properly.
Step-8: Select and Install Radiator Hoses
You need to find radiator hoses that fit the custom engine and radiator combination. The exact hoses you need depend on what combination of water pump your LS engine has, where the engine has been located according to what engine mount adapters you used, and what custom radiator you have. With that many variables, it’s impossible to provide part numbers for hoses that fit. The best thing to do is to bend a coat hanger or TIG welding rod to the shape you need for the upper and lower radiator hoses. Cut it to length and then visit a parts store. If you ordered a custom radiator with a 1½-inch inlet and outlet, the hoses need to be a consistent diameter. If you didn’t, then you also need to note the radiator hose diameter needed on each end. There are hundreds of preformed radiator hoses; if your parts store has a good selection, you will be able to find ones that fits. You may need to do a little trimming for length to fit perfectly.
Step-9: Install Oil Vapor Catch Tank
Most LS engines have one vent tube on each valve cover and another one on the lifter valley plate. This allows oil vapor and pressure from inside the engine to be released. From the factory, this pressure—and specifically the oil vapor—has to be captured and managed for emissions reasons. In a performance application, you want to make sure that the pressure is allowed to escape, and you want to capture the oil vapor to keep things clean under the hood. The easiest way to do this, if you’re running the factory valve covers, is to plumb the lines to a vapor catch can that mounts on the firewall or the radiator core support. There are several aluminum versions as well plastic ones. Essentially, the pressure pushes the oil vapor into the canister, which is designed to let the pressure pass through and release into the atmosphere, but extracts the oil and lets it collect inside the canister. You need to empty the canister periodically, and most have a drain petcock built in to make this easy.
Step-10: Inspect Finished Installation
This is what my LS engine installation looks like when it is finished. In contrast to the LS engine’s original form, which kept all of the modern, high-tech induction and exposed ignition coils, the finished product shows the under-the-hood appearance I wanted, retaining the muscle car heritage of an older Chevelle. This is one reason to opt for an LS engine with a single 4-barrel intake converted with the FAST EZ-EFI fuel injection rather than a port-injected system. The coils are hidden under coil covers from Holley. These are plastic covers that snap onto studs threaded into the stock GM valve covers. They are supposed to mimic a big-block valve cover appearance. The air cleaner is a 14-inch, spun-aluminum assembly with a 1-inch dropped base and a 14 x 3-inch K&N air filter. I painted the air cleaner and the plastic Holley coil covers with Mercedes silver paint. Even with shimming the engine upward and using the 1/4-inch-tall Moroso engine mounts, I was left with nearly 1/2 inch of clearance between the stock steel flat hood and the top of the air cleaner. This is the classic muscle car look, with the modern performance and efficiency of a fuel-injected, computer-controlled LS engine under the hood.
Written by Cole Quinnell and Posted with Permission of CarTechBooks